* [PATCH v3] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter
@ 2023-05-31 7:50 Jinrong Liang
2023-08-16 3:29 ` JinrongLiang
2023-09-28 16:40 ` Sean Christopherson
0 siblings, 2 replies; 3+ messages in thread
From: Jinrong Liang @ 2023-05-31 7:50 UTC (permalink / raw)
To: Sean Christopherson
Cc: Paolo Bonzini, Like Xu, Bagas Sanjaya, Wanpeng Li, Jinrong Liang,
kvm, linux-kernel
From: Jinrong Liang <cloudliang@tencent.com>
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>
---
v3:
- Rebased to 5c291b93e5d6(tag: kvm-x86-next-2023.04.26)
- Revise documentation to enhance user understanding. (Sean)
- Post this patch separately from the selftests changes. (Sean)
v2:
- Wrap the code from the documentation in a block of code; (Bagas Sanjaya)
v1:
https://lore.kernel.org/kvm/20230414110056.19665-5-cloudliang@tencent.com
Documentation/virt/kvm/api.rst | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index a69e91088d76..9f680eb89b2b 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -5122,6 +5122,24 @@ 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
---------------------
base-commit: 5c291b93e5d665380dbecc6944973583f9565ee5
--
2.31.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter
2023-05-31 7:50 [PATCH v3] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter Jinrong Liang
@ 2023-08-16 3:29 ` JinrongLiang
2023-09-28 16:40 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: JinrongLiang @ 2023-08-16 3:29 UTC (permalink / raw)
To: Sean Christopherson, Jinrong Liang
Cc: Paolo Bonzini, Like Xu, Bagas Sanjaya, Wanpeng Li, kvm, linux-kernel
Gentle ping.
在 2023/5/31 15:50, Jinrong Liang 写道:
> From: Jinrong Liang <cloudliang@tencent.com>
>
> 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>
> ---
>
> v3:
> - Rebased to 5c291b93e5d6(tag: kvm-x86-next-2023.04.26)
> - Revise documentation to enhance user understanding. (Sean)
> - Post this patch separately from the selftests changes. (Sean)
>
> v2:
> - Wrap the code from the documentation in a block of code; (Bagas Sanjaya)
>
> v1:
> https://lore.kernel.org/kvm/20230414110056.19665-5-cloudliang@tencent.com
>
> Documentation/virt/kvm/api.rst | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index a69e91088d76..9f680eb89b2b 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -5122,6 +5122,24 @@ 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
> ---------------------
>
>
> base-commit: 5c291b93e5d665380dbecc6944973583f9565ee5
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter
2023-05-31 7:50 [PATCH v3] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter Jinrong Liang
2023-08-16 3:29 ` JinrongLiang
@ 2023-09-28 16:40 ` Sean Christopherson
1 sibling, 0 replies; 3+ messages in thread
From: Sean Christopherson @ 2023-09-28 16:40 UTC (permalink / raw)
To: Sean Christopherson, Jinrong Liang
Cc: Paolo Bonzini, Like Xu, Bagas Sanjaya, Wanpeng Li, Jinrong Liang,
kvm, linux-kernel
On Wed, 31 May 2023 15:50:52 +0800, Jinrong Liang wrote:
> 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.
>
> [...]
Applied to kvm-x86 docs, thanks!
[1/1] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter
https://github.com/kvm-x86/linux/commit/b35babd3abea
--
https://github.com/kvm-x86/linux/tree/next
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-05-31 7:50 [PATCH v3] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter Jinrong Liang
2023-08-16 3:29 ` JinrongLiang
2023-09-28 16:40 ` Sean Christopherson
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