| Message ID | 20241127235312.4048445-1-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: SVM: Remove redundant TLB flush on guest CR4.PGE change | expand |
On Wed, 27 Nov 2024 15:53:12 -0800, Sean Christopherson wrote: > 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. > > [...] Applied to kvm-x86 svm, thanks! [1/1] KVM: SVM: Remove redundant TLB flush on guest CR4.PGE change https://github.com/kvm-x86/linux/commit/036e78a942b4 -- https://github.com/kvm-x86/linux/tree/next
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index dd15cc635655..f39724bf26be 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;
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. Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/svm/svm.c | 5 ----- 1 file changed, 5 deletions(-) base-commit: 4d911c7abee56771b0219a9fbf0120d06bdc9c14