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    SubjectRe: [PATCH v3] KVM: x86/pmu: Add documentation for fixed ctr on PMU filter
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    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

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