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KVM: x86/pmu: Don't tell userspace to save PMU MSRs if PMU is disabled

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Omit all PMU MSRs from the "MSRs to save" list if the PMU is disabled so
that userspace doesn't waste time saving and restoring dummy values.  KVM
provides "error" semantics (read zeros, drop writes) for such known-but-
unsupported MSRs, i.e. has fudged around this issue for quite some time.
Keep the "error" semantics as-is for now, the logic will be cleaned up in
a separate patch.

Cc: Aaron Lewis <aaronlewis@google.com>
Cc: Weijiang Yang <weijiang.yang@intel.com>
Link: https://lore.kernel.org/r/20230124234905.3774678-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2023-01-24 23:49:03 +00:00
parent 2374b7310b
commit c3531edc79
1 changed files with 4 additions and 2 deletions
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6
arch/x86/kvm/x86.c
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@@ -7081,8 +7081,10 @@ static void kvm_init_msr_list(void)
for (i = 0; i < ARRAY_SIZE(msrs_to_save_base); i++)
kvm_probe_msr_to_save(msrs_to_save_base[i]);
for (i = 0; i < ARRAY_SIZE(msrs_to_save_pmu); i++)
kvm_probe_msr_to_save(msrs_to_save_pmu[i]);
if (enable_pmu) {
for (i = 0; i < ARRAY_SIZE(msrs_to_save_pmu); i++)
kvm_probe_msr_to_save(msrs_to_save_pmu[i]);
}
for (i = 0; i < ARRAY_SIZE(emulated_msrs_all); i++) {
if (!static_call(kvm_x86_has_emulated_msr)(NULL, emulated_msrs_all[i]))