[PATCHv4 01/11] KVM: nSVM: Don't sync vmcb02 V_IRQ back to vmcb12 if KVM (L0) is intercepting VINTR

Santosh Shukla
2023-02-27T09:05:37Z

From: Santosh Shukla <Santosh.Shukla@amd.com>

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>
Signed-off-by: Santosh Shukla <Santosh.Shukla@amd.com>
---
v4:
https://lore.kernel.org/all/Y9hybI65So5X2LFg@google.com/
suggested by Sean.

arch/x86/kvm/svm/nested.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 05d38944a6c0..fbade158d368 100644
--- 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;
--
2.25.1