On 2025-04-25 7:15 a.m., Peter Zijlstra wrote:
> On Mon, Mar 24, 2025 at 05:30:50PM +0000, Mingwei Zhang wrote:
>> From: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>>
>> Implement switch_guest_ctx interface for x86 PMU, switch PMI to dedicated
>> KVM_GUEST_PMI_VECTOR at perf guest enter, and switch PMI back to
>> NMI at perf guest exit.
>>
>> Signed-off-by: Xiong Zhang <xiong.y.zhang@xxxxxxxxxxxxxxx>
>> Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
>> Tested-by: Yongwei Ma <yongwei.ma@xxxxxxxxx>
>> Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
>> ---
>> arch/x86/events/core.c | 12 ++++++++++++
>> 1 file changed, 12 insertions(+)
>>
>> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
>> index 8f218ac0d445..28161d6ff26d 100644
>> --- a/arch/x86/events/core.c
>> +++ b/arch/x86/events/core.c
>> @@ -2677,6 +2677,16 @@ static bool x86_pmu_filter(struct pmu *pmu, int cpu)
>> return ret;
>> }
>>
>> +static void x86_pmu_switch_guest_ctx(bool enter, void *data)
>> +{
>> + u32 guest_lvtpc = *(u32 *)data;
>> +
>> + if (enter)
>> + apic_write(APIC_LVTPC, guest_lvtpc);
>> + else
>> + apic_write(APIC_LVTPC, APIC_DM_NMI);
>> +}
>
> This, why can't it use x86_pmu.guest_lvtpc here and call it a day? Why
> is that argument passed around through the generic code only to get back
> here?
The vector has to be from the KVM. However, the current interfaces only
support KVM read perf variables, e.g., perf_get_x86_pmu_capability and
perf_get_hw_event_config.
We need to add an new interface to allow the KVM write a perf variable,
e.g., perf_set_guest_lvtpc.
Thanks,
Kan
