diff options
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/LSM/Yama.rst | 4 | ||||
| -rw-r--r-- | Documentation/admin-guide/README.rst | 3 | ||||
| -rw-r--r-- | Documentation/admin-guide/cgroup-v2.rst | 30 | ||||
| -rw-r--r-- | Documentation/admin-guide/ext4.rst | 574 | ||||
| -rw-r--r-- | Documentation/admin-guide/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 86 | ||||
| -rw-r--r-- | Documentation/admin-guide/l1tf.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/memory-hotplug.rst | 444 | ||||
| -rw-r--r-- | Documentation/admin-guide/pm/intel_pstate.rst | 7 | ||||
| -rw-r--r-- | Documentation/admin-guide/security-bugs.rst | 47 |
11 files changed, 1155 insertions, 44 deletions
diff --git a/Documentation/admin-guide/LSM/Yama.rst b/Documentation/admin-guide/LSM/Yama.rst index 13468ea696b7..d0a060de3973 100644 --- a/Documentation/admin-guide/LSM/Yama.rst +++ b/Documentation/admin-guide/LSM/Yama.rst @@ -64,8 +64,8 @@ The sysctl settings (writable only with ``CAP_SYS_PTRACE``) are: Using ``PTRACE_TRACEME`` is unchanged. 2 - admin-only attach: - only processes with ``CAP_SYS_PTRACE`` may use ptrace - with ``PTRACE_ATTACH``, or through children calling ``PTRACE_TRACEME``. + only processes with ``CAP_SYS_PTRACE`` may use ptrace, either with + ``PTRACE_ATTACH`` or through children calling ``PTRACE_TRACEME``. 3 - no attach: no processes may use ptrace with ``PTRACE_ATTACH`` nor via diff --git a/Documentation/admin-guide/README.rst b/Documentation/admin-guide/README.rst index 15ea785b2dfa..0797eec76be1 100644 --- a/Documentation/admin-guide/README.rst +++ b/Documentation/admin-guide/README.rst @@ -51,8 +51,7 @@ Documentation - There are various README files in the Documentation/ subdirectory: these typically contain kernel-specific installation notes for some - drivers for example. See Documentation/00-INDEX for a list of what - is contained in each file. Please read the + drivers for example. Please read the :ref:`Documentation/process/changes.rst <changes>` file, as it contains information about the problems, which may result by upgrading your kernel. diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst index 184193bcb262..8384c681a4b2 100644 --- a/Documentation/admin-guide/cgroup-v2.rst +++ b/Documentation/admin-guide/cgroup-v2.rst @@ -966,6 +966,12 @@ All time durations are in microseconds. $PERIOD duration. "max" for $MAX indicates no limit. If only one number is written, $MAX is updated. + cpu.pressure + A read-only nested-key file which exists on non-root cgroups. + + Shows pressure stall information for CPU. See + Documentation/accounting/psi.txt for details. + Memory ------ @@ -1127,6 +1133,10 @@ PAGE_SIZE multiple when read back. disk readahead. For now OOM in memory cgroup kills tasks iff shortage has happened inside page fault. + This event is not raised if the OOM killer is not + considered as an option, e.g. for failed high-order + allocations. + oom_kill The number of processes belonging to this cgroup killed by any kind of OOM killer. @@ -1271,6 +1281,12 @@ PAGE_SIZE multiple when read back. higher than the limit for an extended period of time. This reduces the impact on the workload and memory management. + memory.pressure + A read-only nested-key file which exists on non-root cgroups. + + Shows pressure stall information for memory. See + Documentation/accounting/psi.txt for details. + Usage Guidelines ~~~~~~~~~~~~~~~~ @@ -1408,6 +1424,12 @@ IO Interface Files 8:16 rbps=2097152 wbps=max riops=max wiops=max + io.pressure + A read-only nested-key file which exists on non-root cgroups. + + Shows pressure stall information for IO. See + Documentation/accounting/psi.txt for details. + Writeback ~~~~~~~~~ @@ -1857,8 +1879,10 @@ following two functions. wbc_init_bio(@wbc, @bio) Should be called for each bio carrying writeback data and - associates the bio with the inode's owner cgroup. Can be - called anytime between bio allocation and submission. + associates the bio with the inode's owner cgroup and the + corresponding request queue. This must be called after + a queue (device) has been associated with the bio and + before submission. wbc_account_io(@wbc, @page, @bytes) Should be called for each data segment being written out. @@ -1877,7 +1901,7 @@ the configuration, the bio may be executed at a lower priority and if the writeback session is holding shared resources, e.g. a journal entry, may lead to priority inversion. There is no one easy solution for the problem. Filesystems can try to work around specific problem -cases by skipping wbc_init_bio() or using bio_associate_blkcg() +cases by skipping wbc_init_bio() or using bio_associate_create_blkg() directly. diff --git a/Documentation/admin-guide/ext4.rst b/Documentation/admin-guide/ext4.rst new file mode 100644 index 000000000000..e506d3dae510 --- /dev/null +++ b/Documentation/admin-guide/ext4.rst @@ -0,0 +1,574 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================== +ext4 General Information +======================== + +Ext4 is an advanced level of the ext3 filesystem which incorporates +scalability and reliability enhancements for supporting large filesystems +(64 bit) in keeping with increasing disk capacities and state-of-the-art +feature requirements. + +Mailing list: linux-ext4@vger.kernel.org +Web site: http://ext4.wiki.kernel.org + + +Quick usage instructions +======================== + +Note: More extensive information for getting started with ext4 can be +found at the ext4 wiki site at the URL: +http://ext4.wiki.kernel.org/index.php/Ext4_Howto + + - The latest version of e2fsprogs can be found at: + + https://www.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs/ + + or + + http://sourceforge.net/project/showfiles.php?group_id=2406 + + or grab the latest git repository from: + + https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git + + - Create a new filesystem using the ext4 filesystem type: + + # mke2fs -t ext4 /dev/hda1 + + Or to configure an existing ext3 filesystem to support extents: + + # tune2fs -O extents /dev/hda1 + + If the filesystem was created with 128 byte inodes, it can be + converted to use 256 byte for greater efficiency via: + + # tune2fs -I 256 /dev/hda1 + + - Mounting: + + # mount -t ext4 /dev/hda1 /wherever + + - When comparing performance with other filesystems, it's always + important to try multiple workloads; very often a subtle change in a + workload parameter can completely change the ranking of which + filesystems do well compared to others. When comparing versus ext3, + note that ext4 enables write barriers by default, while ext3 does + not enable write barriers by default. So it is useful to use + explicitly specify whether barriers are enabled or not when via the + '-o barriers=[0|1]' mount option for both ext3 and ext4 filesystems + for a fair comparison. When tuning ext3 for best benchmark numbers, + it is often worthwhile to try changing the data journaling mode; '-o + data=writeback' can be faster for some workloads. (Note however that + running mounted with data=writeback can potentially leave stale data + exposed in recently written files in case of an unclean shutdown, + which could be a security exposure in some situations.) Configuring + the filesystem with a large journal can also be helpful for + metadata-intensive workloads. + +Features +======== + +Currently Available +------------------- + +* ability to use filesystems > 16TB (e2fsprogs support not available yet) +* extent format reduces metadata overhead (RAM, IO for access, transactions) +* extent format more robust in face of on-disk corruption due to magics, +* internal redundancy in tree +* improved file allocation (multi-block alloc) +* lift 32000 subdirectory limit imposed by i_links_count[1] +* nsec timestamps for mtime, atime, ctime, create time +* inode version field on disk (NFSv4, Lustre) +* reduced e2fsck time via uninit_bg feature +* journal checksumming for robustness, performance +* persistent file preallocation (e.g for streaming media, databases) +* ability to pack bitmaps and inode tables into larger virtual groups via the + flex_bg feature +* large file support +* inode allocation using large virtual block groups via flex_bg +* delayed allocation +* large block (up to pagesize) support +* efficient new ordered mode in JBD2 and ext4 (avoid using buffer head to force + the ordering) + +[1] Filesystems with a block size of 1k may see a limit imposed by the +directory hash tree having a maximum depth of two. + +Options +======= + +When mounting an ext4 filesystem, the following option are accepted: +(*) == default + + ro + Mount filesystem read only. Note that ext4 will replay the journal (and + thus write to the partition) even when mounted "read only". The mount + options "ro,noload" can be used to prevent writes to the filesystem. + + journal_checksum + Enable checksumming of the journal transactions. This will allow the + recovery code in e2fsck and the kernel to detect corruption in the + kernel. It is a compatible change and will be ignored by older + kernels. + + journal_async_commit + Commit block can be written to disk without waiting for descriptor + blocks. If enabled older kernels cannot mount the device. This will + enable 'journal_checksum' internally. + + journal_path=path, journal_dev=devnum + When the external journal device's major/minor numbers have changed, + these options allow the user to specify the new journal location. The + journal device is identified through either its new major/minor numbers + encoded in devnum, or via a path to the device. + + norecovery, noload + Don't load the journal on mounting. Note that if the filesystem was + not unmounted cleanly, skipping the journal replay will lead to the + filesystem containing inconsistencies that can lead to any number of + problems. + + data=journal + All data are committed into the journal prior to being written into the + main file system. Enabling this mode will disable delayed allocation + and O_DIRECT support. + + data=ordered (*) + All data are forced directly out to the main file system prior to its + metadata being committed to the journal. + + data=writeback + Data ordering is not preserved, data may be written into the main file + system after its metadata has been committed to the journal. + + commit=nrsec (*) + Ext4 can be told to sync all its data and metadata every 'nrsec' + seconds. The default value is 5 seconds. This means that if you lose + your power, you will lose as much as the latest 5 seconds of work (your + filesystem will not be damaged though, thanks to the journaling). This + default value (or any low value) will hurt performance, but it's good + for data-safety. Setting it to 0 will have the same effect as leaving + it at the default (5 seconds). Setting it to very large values will + improve performance. + + barrier=<0|1(*)>, barrier(*), nobarrier + This enables/disables the use of write barriers in the jbd code. + barrier=0 disables, barrier=1 enables. This also requires an IO stack + which can support barriers, and if jbd gets an error on a barrier + write, it will disable again with a warning. Write barriers enforce + proper on-disk ordering of journal commits, making volatile disk write + caches safe to use, at some performance penalty. If your disks are + battery-backed in one way or another, disabling barriers may safely + improve performance. The mount options "barrier" and "nobarrier" can + also be used to enable or disable barriers, for consistency with other + ext4 mount options. + + inode_readahead_blks=n + This tuning parameter controls the maximum number of inode table blocks + that ext4's inode table readahead algorithm will pre-read into the + buffer cache. The default value is 32 blocks. + + nouser_xattr + Disables Extended User Attributes. See the attr(5) manual page for + more information about extended attributes. + + noacl + This option disables POSIX Access Control List support. If ACL support + is enabled in the kernel configuration (CONFIG_EXT4_FS_POSIX_ACL), ACL + is enabled by default on mount. See the acl(5) manual page for more + information about acl. + + bsddf (*) + Make 'df' act like BSD. + + minixdf + Make 'df' act like Minix. + + debug + Extra debugging information is sent to syslog. + + abort + Simulate the effects of calling ext4_abort() for debugging purposes. + This is normally used while remounting a filesystem which is already + mounted. + + errors=remount-ro + Remount the filesystem read-only on an error. + + errors=continue + Keep going on a filesystem error. + + errors=panic + Panic and halt the machine if an error occurs. (These mount options + override the errors behavior specified in the superblock, which can be + configured using tune2fs) + + data_err=ignore(*) + Just print an error message if an error occurs in a file data buffer in + ordered mode. + data_err=abort + Abort the journal if an error occurs in a file data buffer in ordered + mode. + + grpid | bsdgroups + New objects have the group ID of their parent. + + nogrpid (*) | sysvgroups + New objects have the group ID of their creator. + + resgid=n + The group ID which may use the reserved blocks. + + resuid=n + The user ID which may use the reserved blocks. + + sb= + Use alternate superblock at this location. + + quota, noquota, grpquota, usrquota + These options are ignored by the filesystem. They are used only by + quota tools to recognize volumes where quota should be turned on. See + documentation in the quota-tools package for more details + (http://sourceforge.net/projects/linuxquota). + + jqfmt=<quota type>, usrjquota=<file>, grpjquota=<file> + These options tell filesystem details about quota so that quota + information can be properly updated during journal replay. They replace + the above quota options. See documentation in the quota-tools package + for more details (http://sourceforge.net/projects/linuxquota). + + stripe=n + Number of filesystem blocks that mballoc will try to use for allocation + size and alignment. For RAID5/6 systems this should be the number of + data disks * RAID chunk size in file system blocks. + + delalloc (*) + Defer block allocation until just before ext4 writes out the block(s) + in question. This allows ext4 to better allocation decisions more + efficiently. + + nodelalloc + Disable delayed allocation. Blocks are allocated when the data is + copied from userspace to the page cache, either via the write(2) system + call or when an mmap'ed page which was previously unallocated is + written for the first time. + + max_batch_time=usec + Maximum amount of time ext4 should wait for additional filesystem + operations to be batch together with a synchronous write operation. + Since a synchronous write operation is going to force a commit and then + a wait for the I/O complete, it doesn't cost much, and can be a huge + throughput win, we wait for a small amount of time to see if any other + transactions can piggyback on the synchronous write. The algorithm + used is designed to automatically tune for the speed of the disk, by + measuring the amount of time (on average) that it takes to finish + committing a transaction. Call this time the "commit time". If the + time that the transaction has been running is less than the commit + time, ext4 will try sleeping for the commit time to see if other + operations will join the transaction. The commit time is capped by + the max_batch_time, which defaults to 15000us (15ms). This + optimization can be turned off entirely by setting max_batch_time to 0. + + min_batch_time=usec + This parameter sets the commit time (as described above) to be at least + min_batch_time. It defaults to zero microseconds. Increasing this + parameter may improve the throughput of multi-threaded, synchronous + workloads on very fast disks, at the cost of increasing latency. + + journal_ioprio=prio + The I/O priority (from 0 to 7, where 0 is the highest priority) which + should be used for I/O operations submitted by kjournald2 during a + commit operation. This defaults to 3, which is a slightly higher + priority than the default I/O priority. + + auto_da_alloc(*), noauto_da_alloc + Many broken applications don't use fsync() when replacing existing + files via patterns such as fd = open("foo.new")/write(fd,..)/close(fd)/ + rename("foo.new", "foo"), or worse yet, fd = open("foo", + O_TRUNC)/write(fd,..)/close(fd). If auto_da_alloc is enabled, ext4 + will detect the replace-via-rename and replace-via-truncate patterns + and force that any delayed allocation blocks are allocated such that at + the next journal commit, in the default data=ordered mode, the data + blocks of the new file are forced to disk before the rename() operation + is committed. This provides roughly the same level of guarantees as + ext3, and avoids the "zero-length" problem that can happen when a + system crashes before the delayed allocation blocks are forced to disk. + + noinit_itable + Do not initialize any uninitialized inode table blocks in the + background. This feature may be used by installation CD's so that the + install process can complete as quickly as possible; the inode table + initialization process would then be deferred until the next time the + file system is unmounted. + + init_itable=n + The lazy itable init code will wait n times the number of milliseconds + it took to zero out the previous block group's inode table. This + minimizes the impact on the system performance while file system's + inode table is being initialized. + + discard, nodiscard(*) + Controls whether ext4 should issue discard/TRIM commands to the + underlying block device when blocks are freed. This is useful for SSD + devices and sparse/thinly-provisioned LUNs, but it is off by default + until sufficient testing has been done. + + nouid32 + Disables 32-bit UIDs and GIDs. This is for interoperability with + older kernels which only store and expect 16-bit values. + + block_validity(*), noblock_validity + These options enable or disable the in-kernel facility for tracking + filesystem metadata blocks within internal data structures. This + allows multi- block allocator and other routines to notice bugs or + corrupted allocation bitmaps which cause blocks to be allocated which + overlap with filesystem metadata blocks. + + dioread_lock, dioread_nolock + Controls whether or not ext4 should use the DIO read locking. If the + dioread_nolock option is specified ext4 will allocate uninitialized + extent before buffer write and convert the extent to initialized after + IO completes. This approach allows ext4 code to avoid using inode + mutex, which improves scalability on high speed storages. However this + does not work with data journaling and dioread_nolock option will be + ignored with kernel warning. Note that dioread_nolock code path is only + used for extent-based files. Because of the restrictions this options + comprises it is off by default (e.g. dioread_lock). + + max_dir_size_kb=n + This limits the size of directories so that any attempt to expand them + beyond the specified limit in kilobytes will cause an ENOSPC error. + This is useful in memory constrained environments, where a very large + directory can cause severe performance problems or even provoke the Out + Of Memory killer. (For example, if there is only 512mb memory + available, a 176mb directory may seriously cramp the system's style.) + + i_version + Enable 64-bit inode version support. This option is off by default. + + dax + Use direct access (no page cache). See + Documentation/filesystems/dax.txt. Note that this option is + incompatible with data=journal. + +Data Mode +========= +There are 3 different data modes: + +* writeback mode + + In data=writeback mode, ext4 does not journal data at all. This mode provides + a similar level of journaling as that of XFS, JFS, and ReiserFS in its default + mode - metadata journaling. A crash+recovery can cause incorrect data to + appear in files which were written shortly before the crash. This mode will + typically provide the best ext4 performance. + +* ordered mode + + In data=ordered mode, ext4 only officially journals metadata, but it logically + groups metadata information related to data changes with the data blocks into + a single unit called a transaction. When it's time to write the new metadata + out to disk, the associated data blocks are written first. In general, this + mode performs slightly slower than writeback but significantly faster than + journal mode. + +* journal mode + + data=journal mode provides full data and metadata journaling. All new data is + written to the journal first, and then to its final location. In the event of + a crash, the journal can be replayed, bringing both data and metadata into a + consistent state. This mode is the slowest except when data needs to be read + from and written to disk at the same time where it outperforms all others + modes. Enabling this mode will disable delayed allocation and O_DIRECT + support. + +/proc entries +============= + +Information about mounted ext4 file systems can be found in +/proc/fs/ext4. Each mounted filesystem will have a directory in +/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or +/proc/fs/ext4/dm-0). The files in each per-device directory are shown +in table below. + +Files in /proc/fs/ext4/<devname> + + mb_groups + details of multiblock allocator buddy cache of free blocks + +/sys entries +============ + +Information about mounted ext4 file systems can be found in +/sys/fs/ext4. Each mounted filesystem will have a directory in +/sys/fs/ext4 based on its device name (i.e., /sys/fs/ext4/hdc or +/sys/fs/ext4/dm-0). The files in each per-device directory are shown +in table below. + +Files in /sys/fs/ext4/<devname>: + +(see also Documentation/ABI/testing/sysfs-fs-ext4) + + delayed_allocation_blocks + This file is read-only and shows the number of blocks that are dirty in + the page cache, but which do not have their location in the filesystem + allocated yet. + + inode_goal + Tuning parameter which (if non-zero) controls the goal inode used by + the inode allocator in preference to all other allocation heuristics. + This is intended for debugging use only, and should be 0 on production + systems. + + inode_readahead_blks + Tuning parameter which controls the maximum number of inode table + blocks that ext4's inode table readahead algorithm will pre-read into + the buffer cache. + + lifetime_write_kbytes + This file is read-only and shows the number of kilobytes of data that + have been written to this filesystem since it was created. + + max_writeback_mb_bump + The maximum number of megabytes the writeback code will try to write + out before move on to another inode. + + mb_group_prealloc + The multiblock allocator will round up allocation requests to a + multiple of this tuning parameter if the stripe size is not set in the + ext4 superblock + + mb_max_to_scan + The maximum number of extents the multiblock allocator will search to + find the best extent. + + mb_min_to_scan + The minimum number of extents the multiblock allocator will search to + find the best extent. + + mb_order2_req + Tuning parameter which controls the minimum size for requests (as a + power of 2) where the buddy cache is used. + + mb_stats + Controls whether the multiblock allocator should collect statistics, + which are shown during the unmount. 1 means to collect statistics, 0 + means not to collect statistics. + + mb_stream_req + Files which have fewer blocks than this tunable parameter will have + their blocks allocated out of a block group specific preallocation + pool, so that small files are packed closely together. Each large file + will have its blocks allocated out of its own unique preallocation + pool. + + session_write_kbytes + This file is read-only and shows the number of kilobytes of data that + have been written to this filesystem since it was mounted. + + reserved_clusters + This is RW file and contains number of reserved clusters in the file + system which will be used in the specific situations to avoid costly + zeroout, unexpected ENOSPC, or possible data loss. The default is 2% or + 4096 clusters, whichever is smaller and this can be changed however it + can never exceed number of clusters in the file system. If there is not + enough space for the reserved space when mounting the file mount will + _not_ fail. + +Ioctls +====== + +There is some Ext4 specific functionality which can be accessed by applications +through the system call interfaces. The list of all Ext4 specific ioctls are +shown in the table below. + +Table of Ext4 specific ioctls + + EXT4_IOC_GETFLAGS + Get additional attributes associated with inode. The ioctl argument is + an integer bitfield, with bit values described in ext4.h. This ioctl is + an alias for FS_IOC_GETFLAGS. + + EXT4_IOC_SETFLAGS + Set additional attributes associated with inode. The ioctl argument is + an integer bitfield, with bit values described in ext4.h. This ioctl is + an alias for FS_IOC_SETFLAGS. + + EXT4_IOC_GETVERSION, EXT4_IOC_GETVERSION_OLD + Get the inode i_generation number stored for each inode. The + i_generation number is normally changed only when new inode is created + and it is particularly useful for network filesystems. The '_OLD' + version of this ioctl is an alias for FS_IOC_GETVERSION. + + EXT4_IOC_SETVERSION, EXT4_IOC_SETVERSION_OLD + Set the inode i_generation number stored for each inode. The '_OLD' + version of this ioctl is an alias for FS_IOC_SETVERSION. + + EXT4_IOC_GROUP_EXTEND + This ioctl has the same purpose as the resize mount option. It allows + to resize filesystem to the end of the last existing block group, + further resize has to be done with resize2fs, either online, or + offline. The argument points to the unsigned logn number representing + the filesystem new block count. + + EXT4_IOC_MOVE_EXT + Move the block extents from orig_fd (the one this ioctl is pointing to) + to the donor_fd (the one specified in move_extent structure passed as + an argument to this ioctl). Then, exchange inode metadata between + orig_fd and donor_fd. This is especially useful for online + defragmentation, because the allocator has the opportunity to allocate + moved blocks better, ideally into one contiguous extent. + + EXT4_IOC_GROUP_ADD + Add a new group descriptor to an existing or new group descriptor + block. The new group descriptor is described by ext4_new_group_input + structure, which is passed as an argument to this ioctl. This is + especially useful in conjunction with EXT4_IOC_GROUP_EXTEND, which + allows online resize of the filesystem to the end of the last existing + block group. Those two ioctls combined is used in userspace online + resize tool (e.g. resize2fs). + + EXT4_IOC_MIGRATE + This ioctl operates on the filesystem itself. It converts (migrates) + ext3 indirect block mapped inode to ext4 extent mapped inode by walking + through indirect block mapping of the original inode and converting + contiguous block ranges into ext4 extents of the temporary inode. Then, + inodes are swapped. This ioctl might help, when migrating from ext3 to + ext4 filesystem, however suggestion is to create fresh ext4 filesystem + and copy data from the backup. Note, that filesystem has to support + extents for this ioctl to work. + + EXT4_IOC_ALLOC_DA_BLKS + Force all of the delay allocated blocks to be allocated to preserve + application-expected ext3 behaviour. Note that this will also start + triggering a write of the data blocks, but this behaviour may change in + the future as it is not necessary and has been done this way only for + sake of simplicity. + + EXT4_IOC_RESIZE_FS + Resize the filesystem to a new size. The number of blocks of resized + filesystem is passed in via 64 bit integer argument. The kernel + allocates bitmaps and inode table, the userspace tool thus just passes + the new number of blocks. + + EXT4_IOC_SWAP_BOOT + Swap i_blocks and associated attributes (like i_blocks, i_size, + i_flags, ...) from the specified inode with inode EXT4_BOOT_LOADER_INO + (#5). This is typically used to store a boot loader in a secure part of + the filesystem, where it can't be changed by a normal user by accident. + The data blocks of the previous boot loader will be associated with the + given inode. + +References +========== + +kernel source: <file:fs/ext4/> + <file:fs/jbd2/> + +programs: http://e2fsprogs.sourceforge.net/ + +useful links: http://fedoraproject.org/wiki/ext3-devel + http://www.bullopensource.org/ext4/ + http://ext4.wiki.kernel.org/index.php/Main_Page + http://fedoraproject.org/wiki/Features/Ext4 diff --git a/Documentation/admin-guide/index.rst b/Documentation/admin-guide/index.rst index 0873685bab0f..965745d5fb9a 100644 --- a/Documentation/admin-guide/index.rst +++ b/Documentation/admin-guide/index.rst @@ -71,6 +71,7 @@ configure specific aspects of kernel behavior to your liking. java ras bcache + ext4 pm/index thunderbolt LSM/index diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 9871e649ffef..b90fe3b6bc6c 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -856,6 +856,11 @@ causing system reset or hang due to sending INIT from AP to BSP. + disable_counter_freezing [HW] + Disable Intel PMU counter freezing feature. + The feature only exists starting from + Arch Perfmon v4 (Skylake and newer). + disable_ddw [PPC/PSERIES] Disable Dynamic DMA Window support. Use this if to workaround buggy firmware. @@ -1385,6 +1390,11 @@ hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs. If specified, z/VM IUCV HVC accepts connections from listed z/VM user IDs only. + + hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations + which allow the hypervisor to 'idle' the + guest on lock contention. + keep_bootcon [KNL] Do not unregister boot console at start. This is only useful for debugging when something happens in the window @@ -1749,12 +1759,24 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. + iommu.strict= [ARM64] Configure TLB invalidation behaviour + Format: { "0" | "1" } + 0 - Lazy mode. + Request that DMA unmap operations use deferred + invalidation of hardware TLBs, for increased + throughput at the cost of reduced device isolation. + Will fall back to strict mode if not supported by + the relevant IOMMU driver. + 1 - Strict mode (default). + DMA unmap operations invalidate IOMMU hardware TLBs + synchronously. + iommu.passthrough= [ARM64] Configure DMA to bypass the IOMMU by default. Format: { "0" | "1" } 0 - Use IOMMU translation for DMA. 1 - Bypass the IOMMU for DMA. - unset - Use IOMMU translation for DMA. + unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH. io7= [HW] IO7 for Marvel based alpha systems See comment before marvel_specify_io7 in @@ -2274,6 +2296,8 @@ ltpc= [NET] Format: <io>,<irq>,<dma> + lsm.debug [SECURITY] Enable LSM initialization debugging output. + machvec= [IA-64] Force the use of a particular machine-vector (machvec) in a generic kernel. Example: machvec=hpzx1_swiotlb @@ -2404,7 +2428,7 @@ seconds. Use this parameter to check at some other rate. 0 disables periodic checking. - memtest= [KNL,X86,ARM] Enable memtest + memtest= [KNL,X86,ARM,PPC] Enable memtest Format: <integer> default : 0 <disable> Specifies the number of memtest passes to be @@ -3523,6 +3547,12 @@ ramdisk_size= [RAM] Sizes of RAM disks in kilobytes See Documentation/blockdev/ramdisk.txt. + random.trust_cpu={on,off} + [KNL] Enable or disable trusting the use of the + CPU's random number generator (if available) to + fully seed the kernel's CRNG. Default is controlled + by CONFIG_RANDOM_TRUST_CPU. + ras=option[,option,...] [KNL] RAS-specific options cec_disable [X86] @@ -3534,14 +3564,14 @@ In kernels built with CONFIG_RCU_NOCB_CPU=y, set the specified list of CPUs to be no-callback CPUs. - Invocation of these CPUs' RCU callbacks will - be offloaded to "rcuox/N" kthreads created for - that purpose, where "x" is "b" for RCU-bh, "p" - for RCU-preempt, and "s" for RCU-sched, and "N" - is the CPU number. This reduces OS jitter on the - offloaded CPUs, which can be useful for HPC and - real-time workloads. It can also improve energy - efficiency for asymmetric multiprocessors. + Invocation of these CPUs' RCU callbacks will be + offloaded to "rcuox/N" kthreads created for that + purpose, where "x" is "p" for RCU-preempt, and + "s" for RCU-sched, and "N" is the CPU number. + This reduces OS jitter on the offloaded CPUs, + which can be useful for HPC and real-time + workloads. It can also improve energy efficiency + for asymmetric multiprocessors. rcu_nocb_poll [KNL] Rather than requiring that offloaded CPUs @@ -3595,7 +3625,14 @@ Set required age in jiffies for a given grace period before RCU starts soliciting quiescent-state help from - rcu_note_context_switch(). + rcu_note_context_switch(). If not specified, the + kernel will calculate a value based on the most + recent settings of rcutree.jiffies_till_first_fqs + and rcutree.jiffies_till_next_fqs. + This calculated value may be viewed in + rcutree.jiffies_to_sched_qs. Any attempt to + set rcutree.jiffies_to_sched_qs will be + cheerfully overwritten. rcutree.jiffies_till_first_fqs= [KNL] Set delay from grace-period initialization to @@ -3863,12 +3900,6 @@ rcupdate.rcu_self_test= [KNL] Run the RCU early boot self tests - rcupdate.rcu_self_test_bh= [KNL] - Run the RCU bh early boot self tests - - rcupdate.rcu_self_test_sched= [KNL] - Run the RCU sched early boot self tests - rdinit= [KNL] Format: <full_path> Run specified binary instead of /init from the ramdisk, @@ -4604,7 +4635,8 @@ usbcore.old_scheme_first= [USB] Start with the old device initialization - scheme (default 0 = off). + scheme, applies only to low and full-speed devices + (default 0 = off). usbcore.usbfs_memory_mb= [USB] Memory limit (in MB) for buffers allocated by @@ -4819,6 +4851,18 @@ This is actually a boot loader parameter; the value is passed to the kernel using a special protocol. + vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y. + May slow down system boot speed, especially when + enabled on systems with a large amount of memory. + All options are enabled by default, and this + interface is meant to allow for selectively + enabling or disabling specific virtual memory + debugging features. + + Available options are: + P Enable page structure init time poisoning + - Disable all of the above options + vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact size of <nn>. This can be used to increase the minimum size (128MB on x86). It can also be used to @@ -4994,6 +5038,12 @@ Disables the PV optimizations forcing the HVM guest to run as generic HVM guest with no PV drivers. + xen_scrub_pages= [XEN] + Boolean option to control scrubbing pages before giving them back + to Xen, for use by other domains. Can be also changed at runtime + with /sys/devices/system/xen_memory/xen_memory0/scrub_pages. + Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT. + xirc2ps_cs= [NET,PCMCIA] Format: <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]] diff --git a/Documentation/admin-guide/l1tf.rst b/Documentation/admin-guide/l1tf.rst index bae52b845de0..b85dd80510b0 100644 --- a/Documentation/admin-guide/l1tf.rst +++ b/Documentation/admin-guide/l1tf.rst @@ -553,7 +553,7 @@ When nested virtualization is in use, three operating systems are involved: the bare metal hypervisor, the nested hypervisor and the nested virtual machine. VMENTER operations from the nested hypervisor into the nested guest will always be processed by the bare metal hypervisor. If KVM is the -bare metal hypervisor it wiil: +bare metal hypervisor it will: - Flush the L1D cache on every switch from the nested hypervisor to the nested virtual machine, so that the nested hypervisor's secrets are not diff --git a/Documentation/admin-guide/mm/index.rst b/Documentation/admin-guide/mm/index.rst index ceead68c2df7..8edb35f11317 100644 --- a/Documentation/admin-guide/mm/index.rst +++ b/Documentation/admin-guide/mm/index.rst @@ -29,6 +29,7 @@ the Linux memory management. hugetlbpage idle_page_tracking ksm + memory-hotplug numa_memory_policy pagemap soft-dirty diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst new file mode 100644 index 000000000000..5c4432c96c4b --- /dev/null +++ b/Documentation/admin-guide/mm/memory-hotplug.rst @@ -0,0 +1,444 @@ +.. _admin_guide_memory_hotplug: + +============== +Memory Hotplug +============== + +:Created: Jul 28 2007 +:Updated: Add some details about locking internals: Aug 20 2018 + +This document is about memory hotplug including how-to-use and current status. +Because Memory Hotplug is still under development, contents of this text will +be changed often. + +.. contents:: :local: + +.. note:: + + (1) x86_64's has special implementation for memory hotplug. + This text does not describe it. + (2) This text assumes that sysfs is mounted at ``/sys``. + + +Introduction +============ + +Purpose of memory hotplug +------------------------- + +Memory Hotplug allows users to increase/decrease the amount of memory. +Generally, there are two purposes. + +(A) For changing the amount of memory. + This is to allow a feature like capacity on demand. +(B) For installing/removing DIMMs or NUMA-nodes physically. + This is to exchange DIMMs/NUMA-nodes, reduce power consumption, etc. + +(A) is required by highly virtualized environments and (B) is required by +hardware which supports memory power management. + +Linux memory hotplug is designed for both purpose. + +Phases of memory hotplug +------------------------ + +There are 2 phases in Memory Hotplug: + + 1) Physical Memory Hotplug phase + 2) Logical Memory Hotplug phase. + +The First phase is to communicate hardware/firmware and make/erase +environment for hotplugged memory. Basically, this phase is necessary +for the purpose (B), but this is good phase for communication between +highly virtualized environments too. + +When memory is hotplugged, the kernel recognizes new memory, makes new memory +management tables, and makes sysfs files for new memory's operation. + +If firmware supports notification of connection of new memory to OS, +this phase is triggered automatically. ACPI can notify this event. If not, +"probe" operation by system administration is used instead. +(see :ref:`memory_hotplug_physical_mem`). + +Logical Memory Hotplug phase is to change memory state into +available/unavailable for users. Amount of memory from user's view is +changed by this phase. The kernel makes all memory in it as free pages +when a memory range is available. + +In this document, this phase is described as online/offline. + +Logical Memory Hotplug phase is triggered by write of sysfs file by system +administrator. For the hot-add case, it must be executed after Physical Hotplug +phase by hand. +(However, if you writes udev's hotplug scripts for memory hotplug, these +phases can be execute in seamless way.) + +Unit of Memory online/offline operation +--------------------------------------- + +Memory hotplug uses SPARSEMEM memory model which allows memory to be divided +into chunks of the same size. These chunks are called "sections". The size of +a memory section is architecture dependent. For example, power uses 16MiB, ia64 +uses 1GiB. + +Memory sections are combined into chunks referred to as "memory blocks". The +size of a memory block is architecture dependent and represents the logical +unit upon which memory online/offline operations are to be performed. The +default size of a memory block is the same as memory section size unless an +architecture specifies otherwise. (see :ref:`memory_hotplug_sysfs_files`.) + +To determine the size (in bytes) of a memory block please read this file:: + + /sys/devices/system/memory/block_size_bytes + +Kernel Configuration +==================== + +To use memory hotplug feature, kernel must be compiled with following +config options. + +- For all memory hotplug: + - Memory model -> Sparse Memory (``CONFIG_SPARSEMEM``) + - Allow for memory hot-add (``CONFIG_MEMORY_HOTPLUG``) + +- To enable memory removal, the following are also necessary: + - Allow for memory hot remove (``CONFIG_MEMORY_HOTREMOVE``) + - Page Migration (``CONFIG_MIGRATION``) + +- For ACPI memory hotplug, the following are also necessary: + - Memory hotplug (under ACPI Support menu) (``CONFIG_ACPI_HOTPLUG_MEMORY``) + - This option can be kernel module. + +- As a related configuration, if your box has a feature of NUMA-node hotplug + via ACPI, then this option is necessary too. + + - ACPI0004,PNP0A05 and PNP0A06 Container Driver (under ACPI Support menu) + (``CONFIG_ACPI_CONTAINER``). + + This option can be kernel module too. + + +.. _memory_hotplug_sysfs_files: + +sysfs files for memory hotplug +============================== + +All memory blocks have their device information in sysfs. Each memory block +is described under ``/sys/devices/system/memory`` as:: + + /sys/devices/system/memory/memoryXXX + +where XXX is the memory block id. + +For the memory block covered by the sysfs directory. It is expected that all +memory sections in this range are present and no memory holes exist in the +range. Currently there is no way to determine if there is a memory hole, but +the existence of one should not affect the hotplug capabilities of the memory +block. + +For example, assume 1GiB memory block size. A device for a memory starting at +0x100000000 is ``/sys/device/system/memory/memory4``:: + + (0x100000000 / 1Gib = 4) + +This device covers address range [0x100000000 ... 0x140000000) + +Under each memory block, you can see 5 files: + +- ``/sys/devices/system/memory/memoryXXX/phys_index`` +- ``/sys/devices/system/memory/memoryXXX/phys_device`` +- ``/sys/devices/system/memory/memoryXXX/state`` +- ``/sys/devices/system/memory/memoryXXX/removable`` +- ``/sys/devices/system/memory/memoryXXX/valid_zones`` + +=================== ============================================================ +``phys_index`` read-only and contains memory block id, same as XXX. +``state`` read-write + + - at read: contains online/offline state of memory. + - at write: user can specify "online_kernel", + + "online_movable", "online", "offline" command + which will be performed on all sections in the block. +``phys_device`` read-only: designed to show the name of physical memory + device. This is not well implemented now. +``removable`` read-only: contains an integer value indicating + whether the memory block is removable or not + removable. A value of 1 indicates that the memory + block is removable and a value of 0 indicates that + it is not removable. A memory block is removable only if + every section in the block is removable. +``valid_zones`` read-only: designed to show which zones this memory block + can be onlined to. + + The first column shows it`s default zone. + + "memory6/valid_zones: Normal Movable" shows this memoryblock + can be onlined to ZONE_NORMAL by default and to ZONE_MOVABLE + by online_movable. + + "memory7/valid_zones: Movable Normal" shows this memoryblock + can be onlined to ZONE_MOVABLE by default and to ZONE_NORMAL + by online_kernel. +=================== ============================================================ + +.. note:: + + These directories/files appear after physical memory hotplug phase. + +If CONFIG_NUMA is enabled the memoryXXX/ directories can also be accessed +via symbolic links located in the ``/sys/devices/system/node/node*`` directories. + +For example:: + + /sys/devices/system/node/node0/memory9 -> ../../memory/memory9 + +A backlink will also be created:: + + /sys/devices/system/memory/memory9/node0 -> ../../node/node0 + +.. _memory_hotplug_physical_mem: + +Physical memory hot-add phase +============================= + +Hardware(Firmware) Support +-------------------------- + +On x86_64/ia64 platform, memory hotplug by ACPI is supported. + +In general, the firmware (ACPI) which supports memory hotplug defines +memory class object of _HID "PNP0C80". When a notify is asserted to PNP0C80, +Linux's ACPI handler does hot-add memory to the system and calls a hotplug udev +script. This will be done automatically. + +But scripts for memory hotplug are not contained in generic udev package(now). +You may have to write it by yourself or online/offline memory by hand. +Please see :ref:`memory_hotplug_how_to_online_memory` and +:ref:`memory_hotplug_how_to_offline_memory`. + +If firmware supports NUMA-node hotplug, and defines an object _HID "ACPI0004", +"PNP0A05", or "PNP0A06", notification is asserted to it, and ACPI handler +calls hotplug code for all of objects which are defined in it. +If memory device is found, memory hotplug code will be called. + +Notify memory hot-add event by hand +----------------------------------- + +On some architectures, the firmware may not notify the kernel of a memory +hotplug event. Therefore, the memory "probe" interface is supported to +explicitly notify the kernel. This interface depends on +CONFIG_ARCH_MEMORY_PROBE and can be configured on powerpc, sh, and x86 +if hotplug is supported, although for x86 this should be handled by ACPI +notification. + +Probe interface is located at:: + + /sys/devices/system/memory/probe + +You can tell the physical address of new memory to the kernel by:: + + % echo start_address_of_new_memory > /sys/devices/system/memory/probe + +Then, [start_address_of_new_memory, start_address_of_new_memory + +memory_block_size] memory range is hot-added. In this case, hotplug script is +not called (in current implementation). You'll have to online memory by +yourself. Please see :ref:`memory_hotplug_how_to_online_memory`. + +Logical Memory hot-add phase +============================ + +State of memory +--------------- + +To see (online/offline) state of a memory block, read 'state' file:: + + % cat /sys/device/system/memory/memoryXXX/state + + +- If the memory block is online, you'll read "online". +- If the memory block is offline, you'll read "offline". + + +.. _memory_hotplug_how_to_online_memory: + +How to online memory +-------------------- + +When the memory is hot-added, the kernel decides whether or not to "online" +it according to the policy which can be read from "auto_online_blocks" file:: + + % cat /sys/devices/system/memory/auto_online_blocks + +The default depends on the CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config +option. If it is disabled the default is "offline" which means the newly added +memory is not in a ready-to-use state and you have to "online" the newly added +memory blocks manually. Automatic onlining can be requested by writing "online" +to "auto_online_blocks" file:: + + % echo online > /sys/devices/system/memory/auto_online_blocks + +This sets a global policy and impacts all memory blocks that will subsequently +be hotplugged. Currently offline blocks keep their state. It is possible, under +certain circumstances, that some memory blocks will be added but will fail to +online. User space tools can check their "state" files +(``/sys/devices/system/memory/memoryXXX/state``) and try to online them manually. + +If the automatic onlining wasn't requested, failed, or some memory block was +offlined it is possible to change the individual block's state by writing to the +"state" file:: + + % echo online > /sys/devices/system/memory/memoryXXX/state + +This onlining will not change the ZONE type of the target memory block, +If the memory block doesn't belong to any zone an appropriate kernel zone +(usually ZONE_NORMAL) will be used unless movable_node kernel command line +option is specified when ZONE_MOVABLE will be used. + +You can explicitly request to associate it with ZONE_MOVABLE by:: + + % echo online_movable > /sys/devices/system/memory/memoryXXX/state + +.. note:: current limit: this memory block must be adjacent to ZONE_MOVABLE + +Or you can explicitly request a kernel zone (usually ZONE_NORMAL) by:: + + % echo online_kernel > /sys/devices/system/memory/memoryXXX/state + +.. note:: current limit: this memory block must be adjacent to ZONE_NORMAL + +An explicit zone onlining can fail (e.g. when the range is already within +and existing and incompatible zone already). + +After this, memory block XXX's state will be 'online' and the amount of +available memory will be increased. + +This may be changed in future. + +Logical memory remove +===================== + +Memory offline and ZONE_MOVABLE +------------------------------- + +Memory offlining is more complicated than memory online. Because memory offline +has to make the whole memory block be unused, memory offline can fail if +the memory block includes memory which cannot be freed. + +In general, memory offline can use 2 techniques. + +(1) reclaim and free all memory in the memory block. +(2) migrate all pages in the memory block. + +In the current implementation, Linux's memory offline uses method (2), freeing +all pages in the memory block by page migration. But not all pages are +migratable. Under current Linux, migratable pages are anonymous pages and +page caches. For offlining a memory block by migration, the kernel has to +guarantee that the memory block contains only migratable pages. + +Now, a boot option for making a memory block which consists of migratable pages +is supported. By specifying "kernelcore=" or "movablecore=" boot option, you can +create ZONE_MOVABLE...a zone which is just used for movable pages. +(See also Documentation/admin-guide/kernel-parameters.rst) + +Assume the system has "TOTAL" amount of memory at boot time, this boot option +creates ZONE_MOVABLE as following. + +1) When kernelcore=YYYY boot option is used, + Size of memory not for movable pages (not for offline) is YYYY. + Size of memory for movable pages (for offline) is TOTAL-YYYY. + +2) When movablecore=ZZZZ boot option is used, + Size of memory not for movable pages (not for offline) is TOTAL - ZZZZ. + Size of memory for movable pages (for offline) is ZZZZ. + +.. note:: + + Unfortunately, there is no information to show which memory block belongs + to ZONE_MOVABLE. This is TBD. + +.. _memory_hotplug_how_to_offline_memory: + +How to offline memory +--------------------- + +You can offline a memory block by using the same sysfs interface that was used +in memory onlining:: + + % echo offline > /sys/devices/system/memory/memoryXXX/state + +If offline succeeds, the state of the memory block is changed to be "offline". +If it fails, some error core (like -EBUSY) will be returned by the kernel. +Even if a memory block does not belong to ZONE_MOVABLE, you can try to offline +it. If it doesn't contain 'unmovable' memory, you'll get success. + +A memory block under ZONE_MOVABLE is considered to be able to be offlined +easily. But under some busy state, it may return -EBUSY. Even if a memory +block cannot be offlined due to -EBUSY, you can retry offlining it and may be +able to offline it (or not). (For example, a page is referred to by some kernel +internal call and released soon.) + +Consideration: + Memory hotplug's design direction is to make the possibility of memory + offlining higher and to guarantee unplugging memory under any situation. But + it needs more work. Returning -EBUSY under some situation may be good because + the user can decide to retry more or not by himself. Currently, memory + offlining code does some amount of retry with 120 seconds timeout. + +Physical memory remove +====================== + +Need more implementation yet.... + - Notification completion of remove works by OS to firmware. + - Guard from remove if not yet. + + +Locking Internals +================= + +When adding/removing memory that uses memory block devices (i.e. ordinary RAM), +the device_hotplug_lock should be held to: + +- synchronize against online/offline requests (e.g. via sysfs). This way, memory + block devices can only be accessed (.online/.state attributes) by user + space once memory has been fully added. And when removing memory, we + know nobody is in critical sections. +- synchronize against CPU hotplug and similar (e.g. relevant for ACPI and PPC) + +Especially, there is a possible lock inversion that is avoided using +device_hotplug_lock when adding memory and user space tries to online that +memory faster than expected: + +- device_online() will first take the device_lock(), followed by + mem_hotplug_lock +- add_memory_resource() will first take the mem_hotplug_lock, followed by + the device_lock() (while creating the devices, during bus_add_device()). + +As the device is visible to user space before taking the device_lock(), this +can result in a lock inversion. + +onlining/offlining of memory should be done via device_online()/ +device_offline() - to make sure it is properly synchronized to actions +via sysfs. Holding device_hotplug_lock is advised (to e.g. protect online_type) + +When adding/removing/onlining/offlining memory or adding/removing +heterogeneous/device memory, we should always hold the mem_hotplug_lock in +write mode to serialise memory hotplug (e.g. access to global/zone +variables). + +In addition, mem_hotplug_lock (in contrast to device_hotplug_lock) in read +mode allows for a quite efficient get_online_mems/put_online_mems +implementation, so code accessing memory can protect from that memory +vanishing. + + +Future Work +=========== + + - allowing memory hot-add to ZONE_MOVABLE. maybe we need some switch like + sysctl or new control file. + - showing memory block and physical device relationship. + - test and make it better memory offlining. + - support HugeTLB page migration and offlining. + - memmap removing at memory offline. + - physical remove memory. diff --git a/Documentation/admin-guide/pm/intel_pstate.rst b/Documentation/admin-guide/pm/intel_pstate.rst index 8f1d3de449b5..ac6f5c597a56 100644 --- a/Documentation/admin-guide/pm/intel_pstate.rst +++ b/Documentation/admin-guide/pm/intel_pstate.rst @@ -465,6 +465,13 @@ Next, the following policy attributes have special meaning if policy for the time interval between the last two invocations of the driver's utilization update callback by the CPU scheduler for that CPU. +One more policy attribute is present if the `HWP feature is enabled in the +processor <Active Mode With HWP_>`_: + +``base_frequency`` + Shows the base frequency of the CPU. Any frequency above this will be + in the turbo frequency range. + The meaning of these attributes in the `passive mode <Passive Mode_>`_ is the same as for other scaling drivers. diff --git a/Documentation/admin-guide/security-bugs.rst b/Documentation/admin-guide/security-bugs.rst index 30491d91e93d..164bf71149fd 100644 --- a/Documentation/admin-guide/security-bugs.rst +++ b/Documentation/admin-guide/security-bugs.rst @@ -26,23 +26,34 @@ information is helpful. Any exploit code is very helpful and will not be released without consent from the reporter unless it has already been made public. -Disclosure ----------- - -The goal of the Linux kernel security team is to work with the bug -submitter to understand and fix the bug. We prefer to publish the fix as -soon as possible, but try to avoid public discussion of the bug itself -and leave that to others. - -Publishing the fix may be delayed when the bug or the fix is not yet -fully understood, the solution is not well-tested or for vendor -coordination. However, we expect these delays to be short, measurable in -days, not weeks or months. A release date is negotiated by the security -team working with the bug submitter as well as vendors. However, the -kernel security team holds the final say when setting a timeframe. The -timeframe varies from immediate (esp. if it's already publicly known bug) -to a few weeks. As a basic default policy, we expect report date to -release date to be on the order of 7 days. +Disclosure and embargoed information +------------------------------------ + +The security list is not a disclosure channel. For that, see Coordination +below. + +Once a robust fix has been developed, our preference is to release the +fix in a timely fashion, treating it no differently than any of the other +thousands of changes and fixes the Linux kernel project releases every +month. + +However, at the request of the reporter, we will postpone releasing the +fix for up to 5 business days after the date of the report or after the +embargo has lifted; whichever comes first. The only exception to that +rule is if the bug is publicly known, in which case the preference is to +release the fix as soon as it's available. + +Whilst embargoed information may be shared with trusted individuals in +order to develop a fix, such information will not be published alongside +the fix or on any other disclosure channel without the permission of the +reporter. This includes but is not limited to the original bug report +and followup discussions (if any), exploits, CVE information or the +identity of the reporter. + +In other words our only interest is in getting bugs fixed. All other +information submitted to the security list and any followup discussions +of the report are treated confidentially even after the embargo has been +lifted, in perpetuity. Coordination ------------ @@ -68,7 +79,7 @@ may delay the bug handling. If a reporter wishes to have a CVE identifier assigned ahead of public disclosure, they will need to contact the private linux-distros list, described above. When such a CVE identifier is known before a patch is provided, it is desirable to mention it in the commit -message, though. +message if the reporter agrees. Non-disclosure agreements ------------------------- |