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SubjectRe: [PATCH v2 31/32] KVM: nVMX: Don't flush TLB on nested VM transition with EPT enabled
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On 17/03/20 05:52, Sean Christopherson wrote:
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index d816f1366943..a77eab5b0e8a 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -1123,7 +1123,7 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
> }
>
> if (!nested_ept)
> - kvm_mmu_new_cr3(vcpu, cr3, false);
> + kvm_mmu_new_cr3(vcpu, cr3, enable_ept);

Even if enable_ept == false, we could have already scheduled or flushed
the TLB soon due to one of 1) nested_vmx_transition_tlb_flush 2)
vpid_sync_context in prepare_vmcs02 3) the processor doing it for
!enable_vpid.

So for !enable_ept only KVM_REQ_MMU_SYNC is needed, not
KVM_REQ_TLB_FLUSH_CURRENT I think. Worth adding a TODO?

Paolo

> vcpu->arch.cr3 = cr3;
> kvm_register_mark_available(vcpu, VCPU_EXREG_CR3);
> -- 2.24.1

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