KVM: nSVM: Don't sync vmcb02 V_IRQ back to vmcb12 if KVM (L0) is intercepting VINTR

Don't sync vmcb02 V_IRQ back to vmcb12 if KVM (L0) is intercepting
virtual interrupts in order to request an interrupt window, as KVM
has usurped vmcb02's int_ctl.  If an interrupt window opens before
the next VM-Exit, svm_clear_vintr() will restore vmcb12's int_ctl.
If no window opens, V_IRQ will be correctly preserved in vmcb12's
int_ctl (because it was never recognized while L2 was running).

Suggested-by: Sean Christopherson <seanjc@google.com>
Link: https://lkml.kernel.org/r/Y9hybI65So5X2LFg%40google.com
Signed-off-by: Santosh Shukla <Santosh.Shukla@amd.com>
Link: https://lore.kernel.org/r/20230227084016.3368-2-santosh.shukla@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 05d3894..a77055d 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -416,18 +416,17 @@ void nested_sync_control_from_vmcb02(struct vcpu_svm *svm)
 
        /* Only a few fields of int_ctl are written by the processor.  */
        mask = V_IRQ_MASK | V_TPR_MASK;
-       if (!(svm->nested.ctl.int_ctl & V_INTR_MASKING_MASK) &&
-           svm_is_intercept(svm, INTERCEPT_VINTR)) {
-               /*
-                * In order to request an interrupt window, L0 is usurping
-                * svm->vmcb->control.int_ctl and possibly setting V_IRQ
-                * even if it was clear in L1's VMCB.  Restoring it would be
-                * wrong.  However, in this case V_IRQ will remain true until
-                * interrupt_window_interception calls svm_clear_vintr and
-                * restores int_ctl.  We can just leave it aside.
-                */
+       /*
+        * Don't sync vmcb02 V_IRQ back to vmcb12 if KVM (L0) is intercepting
+        * virtual interrupts in order to request an interrupt window, as KVM
+        * has usurped vmcb02's int_ctl.  If an interrupt window opens before
+        * the next VM-Exit, svm_clear_vintr() will restore vmcb12's int_ctl.
+        * If no window opens, V_IRQ will be correctly preserved in vmcb12's
+        * int_ctl (because it was never recognized while L2 was running).
+        */
+       if (svm_is_intercept(svm, INTERCEPT_VINTR) &&
+           !test_bit(INTERCEPT_VINTR, (unsigned long *)svm->nested.ctl.intercepts))
                mask &= ~V_IRQ_MASK;
-       }
 
        if (nested_vgif_enabled(svm))
                mask |= V_GIF_MASK;