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authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-01 15:45:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-01 15:45:27 -0700
commitb23c4771ff62de8ca9b5e4a2d64491b2fb6f8f69 (patch)
tree3ff6b2bdfec161fbc383bba06bab6329e81b02f7 /Documentation/arm64
parentMerge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm (diff)
parentDocumentation: fixes to the maintainer-entry-profile template (diff)
downloadlinux-dev-b23c4771ff62de8ca9b5e4a2d64491b2fb6f8f69.tar.xz
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Merge tag 'docs-5.8' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet: "A fair amount of stuff this time around, dominated by yet another massive set from Mauro toward the completion of the RST conversion. I *really* hope we are getting close to the end of this. Meanwhile, those patches reach pretty far afield to update document references around the tree; there should be no actual code changes there. There will be, alas, more of the usual trivial merge conflicts. Beyond that we have more translations, improvements to the sphinx scripting, a number of additions to the sysctl documentation, and lots of fixes" * tag 'docs-5.8' of git://git.lwn.net/linux: (130 commits) Documentation: fixes to the maintainer-entry-profile template zswap: docs/vm: Fix typo accept_threshold_percent in zswap.rst tracing: Fix events.rst section numbering docs: acpi: fix old http link and improve document format docs: filesystems: add info about efivars content Documentation: LSM: Correct the basic LSM description mailmap: change email for Ricardo Ribalda docs: sysctl/kernel: document unaligned controls Documentation: admin-guide: update bug-hunting.rst docs: sysctl/kernel: document ngroups_max nvdimm: fixes to maintainter-entry-profile Documentation/features: Correct RISC-V kprobes support entry Documentation/features: Refresh the arch support status files Revert "docs: sysctl/kernel: document ngroups_max" docs: move locking-specific documents to locking/ docs: move digsig docs to the security book docs: move the kref doc into the core-api book docs: add IRQ documentation at the core-api book docs: debugging-via-ohci1394.txt: add it to the core-api book docs: fix references for ipmi.rst file ...
Diffstat (limited to 'Documentation/arm64')
-rw-r--r--Documentation/arm64/amu.rst42
-rw-r--r--Documentation/arm64/booting.rst36
2 files changed, 43 insertions, 35 deletions
diff --git a/Documentation/arm64/amu.rst b/Documentation/arm64/amu.rst
index 036783ee327f..452ec8b115c2 100644
--- a/Documentation/arm64/amu.rst
+++ b/Documentation/arm64/amu.rst
@@ -24,13 +24,13 @@ optional external memory-mapped interface.
Version 1 of the Activity Monitors architecture implements a counter group
of four fixed and architecturally defined 64-bit event counters.
-- CPU cycle counter: increments at the frequency of the CPU.
-- Constant counter: increments at the fixed frequency of the system
- clock.
-- Instructions retired: increments with every architecturally executed
- instruction.
-- Memory stall cycles: counts instruction dispatch stall cycles caused by
- misses in the last level cache within the clock domain.
+ - CPU cycle counter: increments at the frequency of the CPU.
+ - Constant counter: increments at the fixed frequency of the system
+ clock.
+ - Instructions retired: increments with every architecturally executed
+ instruction.
+ - Memory stall cycles: counts instruction dispatch stall cycles caused by
+ misses in the last level cache within the clock domain.
When in WFI or WFE these counters do not increment.
@@ -59,11 +59,11 @@ counters, only the presence of the extension.
Firmware (code running at higher exception levels, e.g. arm-tf) support is
needed to:
-- Enable access for lower exception levels (EL2 and EL1) to the AMU
- registers.
-- Enable the counters. If not enabled these will read as 0.
-- Save/restore the counters before/after the CPU is being put/brought up
- from the 'off' power state.
+ - Enable access for lower exception levels (EL2 and EL1) to the AMU
+ registers.
+ - Enable the counters. If not enabled these will read as 0.
+ - Save/restore the counters before/after the CPU is being put/brought up
+ from the 'off' power state.
When using kernels that have this feature enabled but boot with broken
firmware the user may experience panics or lockups when accessing the
@@ -81,10 +81,10 @@ are not trapped in EL2/EL3.
The fixed counters of AMUv1 are accessible though the following system
register definitions:
-- SYS_AMEVCNTR0_CORE_EL0
-- SYS_AMEVCNTR0_CONST_EL0
-- SYS_AMEVCNTR0_INST_RET_EL0
-- SYS_AMEVCNTR0_MEM_STALL_EL0
+ - SYS_AMEVCNTR0_CORE_EL0
+ - SYS_AMEVCNTR0_CONST_EL0
+ - SYS_AMEVCNTR0_INST_RET_EL0
+ - SYS_AMEVCNTR0_MEM_STALL_EL0
Auxiliary platform specific counters can be accessed using
SYS_AMEVCNTR1_EL0(n), where n is a value between 0 and 15.
@@ -97,9 +97,9 @@ Userspace access
Currently, access from userspace to the AMU registers is disabled due to:
-- Security reasons: they might expose information about code executed in
- secure mode.
-- Purpose: AMU counters are intended for system management use.
+ - Security reasons: they might expose information about code executed in
+ secure mode.
+ - Purpose: AMU counters are intended for system management use.
Also, the presence of the feature is not visible to userspace.
@@ -110,8 +110,8 @@ Virtualization
Currently, access from userspace (EL0) and kernelspace (EL1) on the KVM
guest side is disabled due to:
-- Security reasons: they might expose information about code executed
- by other guests or the host.
+ - Security reasons: they might expose information about code executed
+ by other guests or the host.
Any attempt to access the AMU registers will result in an UNDEFINED
exception being injected into the guest.
diff --git a/Documentation/arm64/booting.rst b/Documentation/arm64/booting.rst
index d063c05d5fb0..7552dbc1cc54 100644
--- a/Documentation/arm64/booting.rst
+++ b/Documentation/arm64/booting.rst
@@ -173,8 +173,10 @@ Before jumping into the kernel, the following conditions must be met:
- Caches, MMUs
The MMU must be off.
+
The instruction cache may be on or off, and must not hold any stale
entries corresponding to the loaded kernel image.
+
The address range corresponding to the loaded kernel image must be
cleaned to the PoC. In the presence of a system cache or other
coherent masters with caches enabled, this will typically require
@@ -239,6 +241,7 @@ Before jumping into the kernel, the following conditions must be met:
- The DT or ACPI tables must describe a GICv2 interrupt controller.
For CPUs with pointer authentication functionality:
+
- If EL3 is present:
- SCR_EL3.APK (bit 16) must be initialised to 0b1
@@ -250,18 +253,22 @@ Before jumping into the kernel, the following conditions must be met:
- HCR_EL2.API (bit 41) must be initialised to 0b1
For CPUs with Activity Monitors Unit v1 (AMUv1) extension present:
+
- If EL3 is present:
- CPTR_EL3.TAM (bit 30) must be initialised to 0b0
- CPTR_EL2.TAM (bit 30) must be initialised to 0b0
- AMCNTENSET0_EL0 must be initialised to 0b1111
- AMCNTENSET1_EL0 must be initialised to a platform specific value
- having 0b1 set for the corresponding bit for each of the auxiliary
- counters present.
+
+ - CPTR_EL3.TAM (bit 30) must be initialised to 0b0
+ - CPTR_EL2.TAM (bit 30) must be initialised to 0b0
+ - AMCNTENSET0_EL0 must be initialised to 0b1111
+ - AMCNTENSET1_EL0 must be initialised to a platform specific value
+ having 0b1 set for the corresponding bit for each of the auxiliary
+ counters present.
+
- If the kernel is entered at EL1:
- AMCNTENSET0_EL0 must be initialised to 0b1111
- AMCNTENSET1_EL0 must be initialised to a platform specific value
- having 0b1 set for the corresponding bit for each of the auxiliary
- counters present.
+
+ - AMCNTENSET0_EL0 must be initialised to 0b1111
+ - AMCNTENSET1_EL0 must be initialised to a platform specific value
+ having 0b1 set for the corresponding bit for each of the auxiliary
+ counters present.
The requirements described above for CPU mode, caches, MMUs, architected
timers, coherency and system registers apply to all CPUs. All CPUs must
@@ -305,7 +312,8 @@ following manner:
Documentation/devicetree/bindings/arm/psci.yaml.
- Secondary CPU general-purpose register settings
- x0 = 0 (reserved for future use)
- x1 = 0 (reserved for future use)
- x2 = 0 (reserved for future use)
- x3 = 0 (reserved for future use)
+
+ - x0 = 0 (reserved for future use)
+ - x1 = 0 (reserved for future use)
+ - x2 = 0 (reserved for future use)
+ - x3 = 0 (reserved for future use)