lkml.org 
[lkml]   [2024]   [Apr]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC PATCH 15/41] KVM: x86/pmu: Manage MSR interception for IA32_PERF_GLOBAL_CTRL
From

On 4/12/2024 6:30 AM, Jim Mattson wrote:
> On Thu, Apr 11, 2024 at 2:21 PM Sean Christopherson <seanjc@google.com> wrote:
>> On Fri, Jan 26, 2024, Xiong Zhang wrote:
>>> + if (is_passthrough_pmu_enabled(&vmx->vcpu)) {
>>> + /*
>>> + * Setup auto restore guest PERF_GLOBAL_CTRL MSR at vm entry.
>>> + */
>>> + if (vmentry_ctrl & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
>>> + vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL, 0);
>>> + else {
>>> + i = vmx_find_loadstore_msr_slot(&vmx->msr_autoload.guest,
>>> + MSR_CORE_PERF_GLOBAL_CTRL);
>>> + if (i < 0) {
>>> + i = vmx->msr_autoload.guest.nr++;
>>> + vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT,
>>> + vmx->msr_autoload.guest.nr);
>>> + }
>>> + vmx->msr_autoload.guest.val[i].index = MSR_CORE_PERF_GLOBAL_CTRL;
>>> + vmx->msr_autoload.guest.val[i].value = 0;
>> Eww, no. Just make cpu_has_load_perf_global_ctrl() and VM_EXIT_SAVE_IA32_PERF_GLOBAL_CTRL
>> hard requirements for enabling passthrough mode. And then have clear_atomic_switch_msr()
>> yell if KVM tries to disable loading MSR_CORE_PERF_GLOBAL_CTRL.
> Weren't you just complaining about the PMU version 4 constraint in
> another patch? And here, you are saying, "Don't support anything older
> than Sapphire Rapids."
>
> Sapphire Rapids has PMU version 4, so if we require
> VM_EXIT_SAVE_IA32_PERF_GLOBAL_CTRL, PMU version 4 is irrelevant.

Just clarify Sapphire Rapids has PMU version 5 :).

[    2.687826] Performance Events: XSAVE Architectural LBR, PEBS
fmt4+-baseline,  AnyThread deprecated, *Sapphire Rapids events*, 32-deep
LBR, full-width counters, Intel PMU driver.
[    2.687925] ... version:                   5
[    2.687928] ... bit width:                 48
[    2.687929] ... generic counters:          8

>

\
 
 \ /
  Last update: 2024-05-27 16:39    [W:0.383 / U:0.188 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site