From 036e78a942b4981a21a48751d45eebaf53f4c5c4 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 27 Nov 2024 15:53:12 -0800 Subject: [PATCH] KVM: SVM: Remove redundant TLB flush on guest CR4.PGE change Drop SVM's direct TLB flush when CR4.PGE is toggled and NPT is enabled, as KVM already guarantees TLBs are flushed appropriately. For the call from cr_trap(), kvm_post_set_cr4() requests TLB_FLUSH_GUEST (which is a superset of TLB_FLUSH_CURRENT) when CR4.PGE is toggled, regardless of whether or not KVM is using TDP. The calls from nested_vmcb02_prepare_save() and nested_svm_vmexit() are checking guest (L2) vs. host (L1) CR4, and so a flush is unnecessary as L2 is defined to use a different ASID (from L1's perspective). Lastly, the call from svm_set_cr0() passes in the current CR4 value, i.e. can't toggle PGE. Link: https://lore.kernel.org/r/20241127235312.4048445-1-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/svm.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index dd15cc6356553..f39724bf26be1 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -284,8 +284,6 @@ u32 svm_msrpm_offset(u32 msr) return MSR_INVALID; } -static void svm_flush_tlb_current(struct kvm_vcpu *vcpu); - static int get_npt_level(void) { #ifdef CONFIG_X86_64 @@ -1921,9 +1919,6 @@ void svm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4) unsigned long host_cr4_mce = cr4_read_shadow() & X86_CR4_MCE; unsigned long old_cr4 = vcpu->arch.cr4; - if (npt_enabled && ((old_cr4 ^ cr4) & X86_CR4_PGE)) - svm_flush_tlb_current(vcpu); - vcpu->arch.cr4 = cr4; if (!npt_enabled) { cr4 |= X86_CR4_PAE; -- 2.39.5