Now that nested TLB flushes are properly tracked with a well-maintained separate ASID for L2 and proper handling of L1's TLB flush requests, drop the unconditional flushes and syncs on nested transitions. On a Milan machine, an L1 and L2 guests were booted, both with a single vCPU, and pinned to a single physical CPU to maximize TLB collisions. In this setup, the cpuid_rate microbenchmark [1] showed the following changes with this patch: +--------+--------+-------------------+----------------------+ | L0 | L1 | cpuid_rate (base) | cpuid_rate (patched) | +========+========+===================+======================+ | NPT | NPT | 256621 | 301113 (+17.3%) | | NPT | Shadow | 180017 | 203347 (+12.96%) | | Shadow | Shadow | 177006 | 189150 (+6.86%) | +--------+--------+-------------------+----------------------+ [1]https://lore.kernel.org/kvm/20231109180646.2963718-1-khorenko@xxxxxxxxxxxxx/ Signed-off-by: Yosry Ahmed <yosry.ahmed@xxxxxxxxx> --- arch/x86/kvm/svm/nested.c | 7 ------- 1 file changed, 7 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index 8e40ff21f7353..45a187d4c23d1 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -512,9 +512,6 @@ static void nested_svm_entry_tlb_flush(struct kvm_vcpu *vcpu) svm->nested.last_asid = svm->nested.ctl.asid; kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu); } - /* TODO: optimize unconditional TLB flush/MMU sync */ - kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); } static void nested_svm_exit_tlb_flush(struct kvm_vcpu *vcpu) @@ -530,10 +527,6 @@ static void nested_svm_exit_tlb_flush(struct kvm_vcpu *vcpu) */ if (svm->nested.ctl.tlb_ctl == TLB_CONTROL_FLUSH_ALL_ASID) kvm_make_request(KVM_REQ_TLB_FLUSH_GUEST, vcpu); - - /* TODO: optimize unconditional TLB flush/MMU sync */ - kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); } /* -- 2.48.1.362.g079036d154-goog
