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KVM: SVM: fix calls to is_intercept

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is_intercept takes an INTERCEPT_* constant, not SVM_EXIT_*; because
of this, the compiler was removing the body of the conditionals,
as if is_intercept returned 0.

This unveils a latent bug: when clearing the VINTR intercept,
int_ctl must also be changed in the L1 VMCB (svm->nested.hsave),
just like the intercept itself is also changed in the L1 VMCB.
Otherwise V_IRQ remains set and, due to the VINTR intercept being clear,
we get a spurious injection of a vector 0 interrupt on the next
L2->L1 vmexit.

Reported-by: Qian Cai <cai@lca.pw>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2020-06-08 07:11:47 -04:00
parent 75ad6e8002
commit fb7333dfd8
2 changed files with 4 additions and 2 deletions
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2
arch/x86/kvm/svm/nested.c
View file

@ -258,7 +258,7 @@ void sync_nested_vmcb_control(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) &&
is_intercept(svm, SVM_EXIT_VINTR)) {
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

4
arch/x86/kvm/svm/svm.c
View file

@ -1378,6 +1378,8 @@ static void svm_clear_vintr(struct vcpu_svm *svm)
/* Drop int_ctl fields related to VINTR injection. */
svm->vmcb->control.int_ctl &= mask;
if (is_guest_mode(&svm->vcpu)) {
svm->nested.hsave->control.int_ctl &= mask;
WARN_ON((svm->vmcb->control.int_ctl & V_TPR_MASK) !=
(svm->nested.ctl.int_ctl & V_TPR_MASK));
svm->vmcb->control.int_ctl |= svm->nested.ctl.int_ctl & ~mask;
@ -1999,7 +2001,7 @@ void svm_set_gif(struct vcpu_svm *svm, bool value)
*/
if (vgif_enabled(svm))
clr_intercept(svm, INTERCEPT_STGI);
if (is_intercept(svm, SVM_EXIT_VINTR))
if (is_intercept(svm, INTERCEPT_VINTR))
svm_clear_vintr(svm);
enable_gif(svm);