Commit 59bff30a authored by Randy Dunlap's avatar Randy Dunlap Committed by Catalin Marinas

Documentation: arm64: fix amu.rst doc warnings

Fix bullet list formatting to eliminate doc warnings:

Documentation/arm64/amu.rst:26: WARNING: Unexpected indentation.
Documentation/arm64/amu.rst:60: WARNING: Unexpected indentation.
Documentation/arm64/amu.rst:81: WARNING: Unexpected indentation.
Documentation/arm64/amu.rst:108: WARNING: Unexpected indentation.
Signed-off-by: default avatarRandy Dunlap <rdunlap@infradead.org>
Cc: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 3fabb438
......@@ -23,13 +23,14 @@ 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.
......@@ -57,11 +58,12 @@ 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
......@@ -78,10 +80,11 @@ 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.
......@@ -93,9 +96,10 @@ 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.
......@@ -105,8 +109,9 @@ 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.
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