@@ -23,6 +23,7 @@ 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.
@@ -57,6 +58,7 @@ 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.
@@ -78,6 +80,7 @@ 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
@@ -93,6 +96,7 @@ 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.
@@ -105,6 +109,7 @@ 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.
Add extra blank lines on some places, in order to avoid those warnings when building the docs: 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: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> --- Documentation/arm64/amu.rst | 5 +++++ 1 file changed, 5 insertions(+)