aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/core-api
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2020-01-28 15:38:56 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-01-28 15:38:56 -0800
commita78208e2436963d0b2c7d186277d6e1a9755029a (patch)
tree090caa51386d811a2750aef3dc70cd247f6aa622 /Documentation/core-api
parentMerge tag '5.6-smb3-fixes-and-dfs-and-readdir-improvements' of git://git.samba.org/sfrench/cifs-2.6 (diff)
parentcrypto: arm/chacha - fix build failured when kernel mode NEON is disabled (diff)
downloadlinux-dev-a78208e2436963d0b2c7d186277d6e1a9755029a.tar.xz
linux-dev-a78208e2436963d0b2c7d186277d6e1a9755029a.zip
Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
Pull crypto updates from Herbert Xu: "API: - Removed CRYPTO_TFM_RES flags - Extended spawn grabbing to all algorithm types - Moved hash descsize verification into API code Algorithms: - Fixed recursive pcrypt dead-lock - Added new 32 and 64-bit generic versions of poly1305 - Added cryptogams implementation of x86/poly1305 Drivers: - Added support for i.MX8M Mini in caam - Added support for i.MX8M Nano in caam - Added support for i.MX8M Plus in caam - Added support for A33 variant of SS in sun4i-ss - Added TEE support for Raven Ridge in ccp - Added in-kernel API to submit TEE commands in ccp - Added AMD-TEE driver - Added support for BCM2711 in iproc-rng200 - Added support for AES256-GCM based ciphers for chtls - Added aead support on SEC2 in hisilicon" * 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (244 commits) crypto: arm/chacha - fix build failured when kernel mode NEON is disabled crypto: caam - add support for i.MX8M Plus crypto: x86/poly1305 - emit does base conversion itself crypto: hisilicon - fix spelling mistake "disgest" -> "digest" crypto: chacha20poly1305 - add back missing test vectors and test chunking crypto: x86/poly1305 - fix .gitignore typo tee: fix memory allocation failure checks on drv_data and amdtee crypto: ccree - erase unneeded inline funcs crypto: ccree - make cc_pm_put_suspend() void crypto: ccree - split overloaded usage of irq field crypto: ccree - fix PM race condition crypto: ccree - fix FDE descriptor sequence crypto: ccree - cc_do_send_request() is void func crypto: ccree - fix pm wrongful error reporting crypto: ccree - turn errors to debug msgs crypto: ccree - fix AEAD decrypt auth fail crypto: ccree - fix typo in comment crypto: ccree - fix typos in error msgs crypto: atmel-{aes,sha,tdes} - Retire crypto_platform_data crypto: x86/sha - Eliminate casts on asm implementations ...
Diffstat (limited to 'Documentation/core-api')
-rw-r--r--Documentation/core-api/index.rst1
-rw-r--r--Documentation/core-api/padata.rst169
2 files changed, 170 insertions, 0 deletions
diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
index ab0eae1c153a..ab0b9ec85506 100644
--- a/Documentation/core-api/index.rst
+++ b/Documentation/core-api/index.rst
@@ -39,6 +39,7 @@ Core utilities
../RCU/index
gcc-plugins
symbol-namespaces
+ padata
Interfaces for kernel debugging
diff --git a/Documentation/core-api/padata.rst b/Documentation/core-api/padata.rst
new file mode 100644
index 000000000000..9a24c111781d
--- /dev/null
+++ b/Documentation/core-api/padata.rst
@@ -0,0 +1,169 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================================
+The padata parallel execution mechanism
+=======================================
+
+:Date: December 2019
+
+Padata is a mechanism by which the kernel can farm jobs out to be done in
+parallel on multiple CPUs while retaining their ordering. It was developed for
+use with the IPsec code, which needs to be able to perform encryption and
+decryption on large numbers of packets without reordering those packets. The
+crypto developers made a point of writing padata in a sufficiently general
+fashion that it could be put to other uses as well.
+
+Usage
+=====
+
+Initializing
+------------
+
+The first step in using padata is to set up a padata_instance structure for
+overall control of how jobs are to be run::
+
+ #include <linux/padata.h>
+
+ struct padata_instance *padata_alloc_possible(const char *name);
+
+'name' simply identifies the instance.
+
+There are functions for enabling and disabling the instance::
+
+ int padata_start(struct padata_instance *pinst);
+ void padata_stop(struct padata_instance *pinst);
+
+These functions are setting or clearing the "PADATA_INIT" flag; if that flag is
+not set, other functions will refuse to work. padata_start() returns zero on
+success (flag set) or -EINVAL if the padata cpumask contains no active CPU
+(flag not set). padata_stop() clears the flag and blocks until the padata
+instance is unused.
+
+Finally, complete padata initialization by allocating a padata_shell::
+
+ struct padata_shell *padata_alloc_shell(struct padata_instance *pinst);
+
+A padata_shell is used to submit a job to padata and allows a series of such
+jobs to be serialized independently. A padata_instance may have one or more
+padata_shells associated with it, each allowing a separate series of jobs.
+
+Modifying cpumasks
+------------------
+
+The CPUs used to run jobs can be changed in two ways, programatically with
+padata_set_cpumask() or via sysfs. The former is defined::
+
+ int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
+ cpumask_var_t cpumask);
+
+Here cpumask_type is one of PADATA_CPU_PARALLEL or PADATA_CPU_SERIAL, where a
+parallel cpumask describes which processors will be used to execute jobs
+submitted to this instance in parallel and a serial cpumask defines which
+processors are allowed to be used as the serialization callback processor.
+cpumask specifies the new cpumask to use.
+
+There may be sysfs files for an instance's cpumasks. For example, pcrypt's
+live in /sys/kernel/pcrypt/<instance-name>. Within an instance's directory
+there are two files, parallel_cpumask and serial_cpumask, and either cpumask
+may be changed by echoing a bitmask into the file, for example::
+
+ echo f > /sys/kernel/pcrypt/pencrypt/parallel_cpumask
+
+Reading one of these files shows the user-supplied cpumask, which may be
+different from the 'usable' cpumask.
+
+Padata maintains two pairs of cpumasks internally, the user-supplied cpumasks
+and the 'usable' cpumasks. (Each pair consists of a parallel and a serial
+cpumask.) The user-supplied cpumasks default to all possible CPUs on instance
+allocation and may be changed as above. The usable cpumasks are always a
+subset of the user-supplied cpumasks and contain only the online CPUs in the
+user-supplied masks; these are the cpumasks padata actually uses. So it is
+legal to supply a cpumask to padata that contains offline CPUs. Once an
+offline CPU in the user-supplied cpumask comes online, padata is going to use
+it.
+
+Changing the CPU masks are expensive operations, so it should not be done with
+great frequency.
+
+Running A Job
+-------------
+
+Actually submitting work to the padata instance requires the creation of a
+padata_priv structure, which represents one job::
+
+ struct padata_priv {
+ /* Other stuff here... */
+ void (*parallel)(struct padata_priv *padata);
+ void (*serial)(struct padata_priv *padata);
+ };
+
+This structure will almost certainly be embedded within some larger
+structure specific to the work to be done. Most of its fields are private to
+padata, but the structure should be zeroed at initialisation time, and the
+parallel() and serial() functions should be provided. Those functions will
+be called in the process of getting the work done as we will see
+momentarily.
+
+The submission of the job is done with::
+
+ int padata_do_parallel(struct padata_shell *ps,
+ struct padata_priv *padata, int *cb_cpu);
+
+The ps and padata structures must be set up as described above; cb_cpu
+points to the preferred CPU to be used for the final callback when the job is
+done; it must be in the current instance's CPU mask (if not the cb_cpu pointer
+is updated to point to the CPU actually chosen). The return value from
+padata_do_parallel() is zero on success, indicating that the job is in
+progress. -EBUSY means that somebody, somewhere else is messing with the
+instance's CPU mask, while -EINVAL is a complaint about cb_cpu not being in the
+serial cpumask, no online CPUs in the parallel or serial cpumasks, or a stopped
+instance.
+
+Each job submitted to padata_do_parallel() will, in turn, be passed to
+exactly one call to the above-mentioned parallel() function, on one CPU, so
+true parallelism is achieved by submitting multiple jobs. parallel() runs with
+software interrupts disabled and thus cannot sleep. The parallel()
+function gets the padata_priv structure pointer as its lone parameter;
+information about the actual work to be done is probably obtained by using
+container_of() to find the enclosing structure.
+
+Note that parallel() has no return value; the padata subsystem assumes that
+parallel() will take responsibility for the job from this point. The job
+need not be completed during this call, but, if parallel() leaves work
+outstanding, it should be prepared to be called again with a new job before
+the previous one completes.
+
+Serializing Jobs
+----------------
+
+When a job does complete, parallel() (or whatever function actually finishes
+the work) should inform padata of the fact with a call to::
+
+ void padata_do_serial(struct padata_priv *padata);
+
+At some point in the future, padata_do_serial() will trigger a call to the
+serial() function in the padata_priv structure. That call will happen on
+the CPU requested in the initial call to padata_do_parallel(); it, too, is
+run with local software interrupts disabled.
+Note that this call may be deferred for a while since the padata code takes
+pains to ensure that jobs are completed in the order in which they were
+submitted.
+
+Destroying
+----------
+
+Cleaning up a padata instance predictably involves calling the three free
+functions that correspond to the allocation in reverse::
+
+ void padata_free_shell(struct padata_shell *ps);
+ void padata_stop(struct padata_instance *pinst);
+ void padata_free(struct padata_instance *pinst);
+
+It is the user's responsibility to ensure all outstanding jobs are complete
+before any of the above are called.
+
+Interface
+=========
+
+.. kernel-doc:: include/linux/padata.h
+.. kernel-doc:: kernel/padata.c