KVM: x86: Rework INIT and SIPI handling
A VCPU sending INIT or SIPI to some other VCPU races for setting the
remote VCPU's mp_state. When we were unlucky, KVM_MP_STATE_INIT_RECEIVED
was overwritten by kvm_emulate_halt and, thus, got lost.
This introduces APIC events for those two signals, keeping them in
kvm_apic until kvm_apic_accept_events is run over the target vcpu
context. kvm_apic_has_events reports to kvm_arch_vcpu_runnable if there
are pending events, thus if vcpu blocking should end.
The patch comes with the side effect of effectively obsoleting
KVM_MP_STATE_SIPI_RECEIVED. We still accept it from user space, but
immediately translate it to KVM_MP_STATE_INIT_RECEIVED + KVM_APIC_SIPI.
The vcpu itself will no longer enter the KVM_MP_STATE_SIPI_RECEIVED
state. That also means we no longer exit to user space after receiving a
SIPI event.
Furthermore, we already reset the VCPU on INIT, only fixing up the code
segment later on when SIPI arrives. Moreover, we fix INIT handling for
the BSP: it never enter wait-for-SIPI but directly starts over on INIT.
Tested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 02b51dd..a8e9369 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -731,7 +731,11 @@
case APIC_DM_INIT:
if (!trig_mode || level) {
result = 1;
- vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
+ /* assumes that there are only KVM_APIC_INIT/SIPI */
+ apic->pending_events = (1UL << KVM_APIC_INIT);
+ /* make sure pending_events is visible before sending
+ * the request */
+ smp_wmb();
kvm_make_request(KVM_REQ_EVENT, vcpu);
kvm_vcpu_kick(vcpu);
} else {
@@ -743,13 +747,13 @@
case APIC_DM_STARTUP:
apic_debug("SIPI to vcpu %d vector 0x%02x\n",
vcpu->vcpu_id, vector);
- if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
- result = 1;
- vcpu->arch.sipi_vector = vector;
- vcpu->arch.mp_state = KVM_MP_STATE_SIPI_RECEIVED;
- kvm_make_request(KVM_REQ_EVENT, vcpu);
- kvm_vcpu_kick(vcpu);
- }
+ result = 1;
+ apic->sipi_vector = vector;
+ /* make sure sipi_vector is visible for the receiver */
+ smp_wmb();
+ set_bit(KVM_APIC_SIPI, &apic->pending_events);
+ kvm_make_request(KVM_REQ_EVENT, vcpu);
+ kvm_vcpu_kick(vcpu);
break;
case APIC_DM_EXTINT:
@@ -1860,6 +1864,34 @@
addr);
}
+void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
+{
+ struct kvm_lapic *apic = vcpu->arch.apic;
+ unsigned int sipi_vector;
+
+ if (!kvm_vcpu_has_lapic(vcpu))
+ return;
+
+ if (test_and_clear_bit(KVM_APIC_INIT, &apic->pending_events)) {
+ kvm_lapic_reset(vcpu);
+ kvm_vcpu_reset(vcpu);
+ if (kvm_vcpu_is_bsp(apic->vcpu))
+ vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+ else
+ vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
+ }
+ if (test_and_clear_bit(KVM_APIC_SIPI, &apic->pending_events) &&
+ vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
+ /* evaluate pending_events before reading the vector */
+ smp_rmb();
+ sipi_vector = apic->sipi_vector;
+ pr_debug("vcpu %d received sipi with vector # %x\n",
+ vcpu->vcpu_id, sipi_vector);
+ kvm_vcpu_deliver_sipi_vector(vcpu, sipi_vector);
+ vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+ }
+}
+
void kvm_lapic_init(void)
{
/* do not patch jump label more than once per second */