KVM: VMX: Invalidate hv_tlb_eptp to denote an EPTP mismatch

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.

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305183123.3978098-7-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 67457a7..2dc7e28 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -500,32 +500,44 @@ 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;
+       int ret = 0, i, nr_unique_valid_eptps;
        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)) {
+               nr_unique_valid_eptps = 0;
 
+               /*
+                * Flush all valid EPTPs, and see if all vCPUs have converged
+                * on a common EPTP, in which case future flushes can skip the
+                * loop and flush the common EPTP.
+                */
                kvm_for_each_vcpu(i, vcpu, kvm) {
                        tmp_eptp = to_vmx(vcpu)->ept_pointer;
                        if (!VALID_PAGE(tmp_eptp) ||
                            tmp_eptp == kvm_vmx->hv_tlb_eptp)
                                continue;
 
-                       if (!VALID_PAGE(kvm_vmx->hv_tlb_eptp))
+                       /*
+                        * Set the tracked EPTP to the first valid EPTP.  Keep
+                        * this EPTP for the entirety of the loop even if more
+                        * EPTPs are encountered as a low effort optimization
+                        * to avoid flushing the same (first) EPTP again.
+                        */
+                       if (++nr_unique_valid_eptps == 1)
                                kvm_vmx->hv_tlb_eptp = tmp_eptp;
-                       else
-                               kvm_vmx->ept_pointers_match
-                                       = EPT_POINTERS_MISMATCH;
 
                        ret |= hv_remote_flush_eptp(tmp_eptp, range);
                }
-               if (kvm_vmx->ept_pointers_match == EPT_POINTERS_MISMATCH)
+
+               /*
+                * The optimized flush of a single EPTP can't be used if there
+                * are multiple valid EPTPs (obviously).
+                */
+               if (nr_unique_valid_eptps > 1)
                        kvm_vmx->hv_tlb_eptp = INVALID_PAGE;
-       } else if (VALID_PAGE(kvm_vmx->hv_tlb_eptp)) {
+       } else {
                ret = hv_remote_flush_eptp(kvm_vmx->hv_tlb_eptp, range);
        }
 
@@ -3105,8 +3117,7 @@ static void vmx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa,
                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 f846cf3..fb7b200 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -338,12 +338,6 @@ 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;
 
@@ -352,7 +346,6 @@ 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;
 };