vmx_apic_init_signal_blocked is buggy in that it returns true
even in VMX non-root mode. In non-root mode, however, INITs
are not latched, they just cause a vmexit. Previously,
KVM was waiting for them to be processed when kvm_apic_accept_events
and in the meanwhile it ate the SIPIs that the processor received.
However, in order to implement the wait-for-SIPI activity state,
KVM will have to process KVM_APIC_SIPI in vmx_check_nested_events,
and it will not be possible anymore to disregard SIPIs in non-root
mode as the code is currently doing.
By calling kvm_x86_ops.nested_ops->check_events, we can force a vmexit
(with the side-effect of latching INITs) before incorrectly injecting
an INIT or SIPI in a guest, and therefore vmx_apic_init_signal_blocked
can do the right thing.
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/lapic.c | 30 ++++++++++++++++++++++++++----
arch/x86/kvm/vmx/vmx.c | 2 +-
2 files changed, 27 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 105e7859d1f2..e3ee597ff540 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2843,14 +2843,35 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
{
struct kvm_lapic *apic = vcpu->arch.apic;
u8 sipi_vector;
+ int r;
unsigned long pe;
- if (!lapic_in_kernel(vcpu) || !apic->pending_events)
+ if (!lapic_in_kernel(vcpu))
+ return;
+
+ /*
+ * Read pending events before calling the check_events
+ * callback.
+ */
+ pe = smp_load_acquire(&apic->pending_events);
+ if (!pe)
return;
+ if (is_guest_mode(vcpu)) {
+ r = kvm_x86_ops.nested_ops->check_events(vcpu);
+ if (r < 0)
+ return;
+ /*
+ * If an event has happened and caused a vmexit,
+ * we know INITs are latched and therefore
+ * we will not incorrectly deliver an APIC
+ * event instead of a vmexit.
+ */
+ }
+
/*
* INITs are latched while CPU is in specific states
- * (SMM, VMX non-root mode, SVM with GIF=0).
+ * (SMM, VMX root mode, SVM with GIF=0).
* Because a CPU cannot be in these states immediately
* after it has processed an INIT signal (and thus in
* KVM_MP_STATE_INIT_RECEIVED state), just eat SIPIs
@@ -2858,13 +2879,13 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
*/
if (kvm_vcpu_latch_init(vcpu)) {
WARN_ON_ONCE(vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED);
- if (test_bit(KVM_APIC_SIPI, &apic->pending_events))
+ if (test_bit(KVM_APIC_SIPI, &pe))
clear_bit(KVM_APIC_SIPI, &apic->pending_events);
return;
}
- pe = xchg(&apic->pending_events, 0);
if (test_bit(KVM_APIC_INIT, &pe)) {
+ clear_bit(KVM_APIC_INIT, &apic->pending_events);
kvm_vcpu_reset(vcpu, true);
if (kvm_vcpu_is_bsp(apic->vcpu))
vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
@@ -2873,6 +2894,7 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
}
if (test_bit(KVM_APIC_SIPI, &pe) &&
vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
+ clear_bit(KVM_APIC_SIPI, &apic->pending_events);
/* evaluate pending_events before reading the vector */
smp_rmb();
sipi_vector = apic->sipi_vector;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 47b8357b9751..64339121a4f0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7558,7 +7558,7 @@ static void enable_smi_window(struct kvm_vcpu *vcpu)
static bool vmx_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
{
- return to_vmx(vcpu)->nested.vmxon;
+ return to_vmx(vcpu)->nested.vmxon && !is_guest_mode(vcpu);
}
static void vmx_migrate_timers(struct kvm_vcpu *vcpu)
--
2.26.2
