From c3531edc79a7adbe4451d34084e8bf227c022872 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 24 Jan 2023 23:49:03 +0000 Subject: [PATCH] KVM: x86/pmu: Don't tell userspace to save PMU MSRs if PMU is disabled 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 Cc: Weijiang Yang Link: https://lore.kernel.org/r/20230124234905.3774678-5-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 9b6e1af63531..25da2cc09e55 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -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]))