KVM: VMX: Skip additional Hyper-V TLB EPTP flushes if one fails

Skip additional EPTP flushes if one fails when processing EPTPs for
Hyper-V's paravirt TLB flushing.  If _any_ flush fails, KVM falls back
to a full global flush, i.e. additional flushes are unnecessary (and
will likely fail anyways).

Continue processing the loop unless a mismatch was already detected,
e.g. to handle the case where the first flush fails and there is a
yet-to-be-detected mismatch.

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: <20210305183123.3978098-11-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 3792f8f..4c665a8 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -528,7 +528,15 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
                        if (++nr_unique_valid_eptps == 1)
                                kvm_vmx->hv_tlb_eptp = tmp_eptp;
 
-                       ret |= hv_remote_flush_eptp(tmp_eptp, range);
+                       if (!ret)
+                               ret = hv_remote_flush_eptp(tmp_eptp, range);
+
+                       /*
+                        * Stop processing EPTPs if a failure occurred and
+                        * there is already a detected EPTP mismatch.
+                        */
+                       if (ret && nr_unique_valid_eptps > 1)
+                               break;
                }
 
                /*