KVM: SVM: fix interrupt injection (apic->isr_count always 0)

In commit b4eef9b36db4, we started to use hwapic_isr_update() != NULL
instead of kvm_apic_vid_enabled(vcpu->kvm).  This didn't work because
SVM had it defined and "apicv" path in apic_{set,clear}_isr() does not
change apic->isr_count, because it should always be 1.  The initial
value of apic->isr_count was based on kvm_apic_vid_enabled(vcpu->kvm),
which is always 0 for SVM, so KVM could have injected interrupts when it
shouldn't.

Fix it by implicitly setting SVM's hwapic_isr_update to NULL and make the
initial isr_count depend on hwapic_isr_update() for good measure.

Fixes: b4eef9b36db4 ("kvm: x86: vmx: NULL out hwapic_isr_update() in case of !enable_apicv")
Reported-and-tested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e55b5fc344eb..bd4e34de24c7 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1572,7 +1572,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu)
                 apic_set_reg(apic, APIC_TMR + 0x10 * i, 0);
         }
         apic->irr_pending = kvm_apic_vid_enabled(vcpu->kvm);
-        apic->isr_count = kvm_apic_vid_enabled(vcpu->kvm);
+        apic->isr_count = kvm_x86_ops->hwapic_isr_update ? 1 : 0;
         apic->highest_isr_cache = -1;
         update_divide_count(apic);
         atomic_set(&apic->lapic_timer.pending, 0);
@@ -1782,7 +1782,7 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
         update_divide_count(apic);
         start_apic_timer(apic);
         apic->irr_pending = true;
-        apic->isr_count = kvm_apic_vid_enabled(vcpu->kvm) ?
+        apic->isr_count = kvm_x86_ops->hwapic_isr_update ?
                                 1 : count_vectors(apic->regs + APIC_ISR);
         apic->highest_isr_cache = -1;
         if (kvm_x86_ops->hwapic_irr_update)