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SubjectRe: [PATCH v2 05/10] KVM: VMX: Invalidate hv_tlb_eptp to denote an EPTP mismatch
Date
Sean Christopherson <sean.j.christopherson@intel.com> writes:

> Drop the dedicated 'ept_pointers_match' field in favor of stuffing
> 'hv_tlb_eptp' with INVALID_PAGE to mark it as invalid, i.e. to denote
> that there is at least one EPTP mismatch. Use a local variable to
> track whether or not a mismatch is detected so that hv_tlb_eptp can be
> used to skip redundant flushes.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 16 ++++++++--------
> arch/x86/kvm/vmx/vmx.h | 7 -------
> 2 files changed, 8 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 52cb9eec1db3..4dfde8b64750 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -498,13 +498,13 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
> struct kvm_vmx *kvm_vmx = to_kvm_vmx(kvm);
> struct kvm_vcpu *vcpu;
> int ret = 0, i;
> + bool mismatch;
> u64 tmp_eptp;
>
> spin_lock(&kvm_vmx->ept_pointer_lock);
>
> - if (kvm_vmx->ept_pointers_match != EPT_POINTERS_MATCH) {
> - kvm_vmx->ept_pointers_match = EPT_POINTERS_MATCH;
> - kvm_vmx->hv_tlb_eptp = INVALID_PAGE;
> + if (!VALID_PAGE(kvm_vmx->hv_tlb_eptp)) {
> + mismatch = false;
>
> kvm_for_each_vcpu(i, vcpu, kvm) {
> tmp_eptp = to_vmx(vcpu)->ept_pointer;
> @@ -515,12 +515,13 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
> if (!VALID_PAGE(kvm_vmx->hv_tlb_eptp))
> kvm_vmx->hv_tlb_eptp = tmp_eptp;
> else
> - kvm_vmx->ept_pointers_match
> - = EPT_POINTERS_MISMATCH;
> + mismatch = true;
>
> ret |= hv_remote_flush_eptp(tmp_eptp, range);
> }
> - } else if (VALID_PAGE(kvm_vmx->hv_tlb_eptp)) {
> + if (mismatch)
> + kvm_vmx->hv_tlb_eptp = INVALID_PAGE;
> + } else {
> ret = hv_remote_flush_eptp(kvm_vmx->hv_tlb_eptp, range);
> }

Personally, I find double negations like 'mismatch = false' hard to read
:-). What if we write this all like

if (!VALID_PAGE(kvm_vmx->hv_tlb_eptp)) {
kvm_vmx->hv_tlb_eptp = to_vmx(vcpu0)->ept_pointer;
kvm_for_each_vcpu() {
tmp_eptp = to_vmx(vcpu)->ept_pointer;
if (!VALID_PAGE(tmp_eptp) || tmp_eptp != kvm_vmx->hv_tlb_eptp)
kvm_vmx->hv_tlb_eptp = INVALID_PAGE;

if (VALID_PAGE(tmp_eptp))
ret |= hv_remote_flush_eptp(tmp_eptp, range);
}
} else {
ret = hv_remote_flush_eptp(kvm_vmx->hv_tlb_eptp, range);
}

(not tested and I've probably missed something)

>
> @@ -3042,8 +3043,7 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, unsigned long pgd,
> if (kvm_x86_ops.tlb_remote_flush) {
> spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
> to_vmx(vcpu)->ept_pointer = eptp;
> - to_kvm_vmx(kvm)->ept_pointers_match
> - = EPT_POINTERS_CHECK;
> + to_kvm_vmx(kvm)->hv_tlb_eptp = INVALID_PAGE;
> spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
> }
>
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 3d557a065c01..e8d7d07b2020 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -288,12 +288,6 @@ struct vcpu_vmx {
> } shadow_msr_intercept;
> };
>
> -enum ept_pointers_status {
> - EPT_POINTERS_CHECK = 0,
> - EPT_POINTERS_MATCH = 1,
> - EPT_POINTERS_MISMATCH = 2
> -};
> -
> struct kvm_vmx {
> struct kvm kvm;
>
> @@ -302,7 +296,6 @@ struct kvm_vmx {
> gpa_t ept_identity_map_addr;
>
> hpa_t hv_tlb_eptp;
> - enum ept_pointers_status ept_pointers_match;
> spinlock_t ept_pointer_lock;
> };

--
Vitaly

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