diff options
| author | Jinrong Liang <cloudliang@tencent.com> | 2023-05-31 15:50:52 +0800 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2023-09-27 14:23:51 -0700 |
| commit | b35babd3abea081de0611ce0d5b85281c18c52c7 (patch) | |
| tree | fbb5994f07dd588fe75060559dc373b38e633384 /Documentation/virt | |
| parent | 78b5605d44e65cb2e07181fcbcde8c76ad5b07b1 (diff) | |
KVM: x86/pmu: Add documentation for fixed ctr on PMU filter
Update the documentation for the KVM_SET_PMU_EVENT_FILTER ioctl
to include a detailed description of how fixed performance events
are handled in the pmu filter. The action and fixed_counter_bitmap
members of the pmu filter to determine whether fixed performance
events can be programmed by the guest. This information is helpful
for correctly configuring the fixed_counter_bitmap and action fields
to filter fixed performance events.
Suggested-by: Like Xu <likexu@tencent.com>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/oe-kbuild-all/202304150850.rx4UDDsB-lkp@intel.com
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Link: https://lore.kernel.org/r/20230531075052.43239-1-cloudliang@tencent.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'Documentation/virt')
| -rw-r--r-- | Documentation/virt/kvm/api.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index fda7f7b0115e..67347d827242 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5124,6 +5124,24 @@ Valid values for 'action':: #define KVM_PMU_EVENT_ALLOW 0 #define KVM_PMU_EVENT_DENY 1 +Via this API, KVM userspace can also control the behavior of the VM's fixed +counters (if any) by configuring the "action" and "fixed_counter_bitmap" fields. + +Specifically, KVM follows the following pseudo-code when determining whether to +allow the guest FixCtr[i] to count its pre-defined fixed event:: + + FixCtr[i]_is_allowed = (action == ALLOW) && (bitmap & BIT(i)) || + (action == DENY) && !(bitmap & BIT(i)); + FixCtr[i]_is_denied = !FixCtr[i]_is_allowed; + +KVM always consumes fixed_counter_bitmap, it's userspace's responsibility to +ensure fixed_counter_bitmap is set correctly, e.g. if userspace wants to define +a filter that only affects general purpose counters. + +Note, the "events" field also applies to fixed counters' hardcoded event_select +and unit_mask values. "fixed_counter_bitmap" has higher priority than "events" +if there is a contradiction between the two. + 4.121 KVM_PPC_SVM_OFF --------------------- |