From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
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.
Fix this by raising requests on the sender side that will then be
handled synchronously over the target VCPU context.
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
Changes in v2:
- check transition to INIT_RECEIVED in vcpu_enter_guest
- removed return value of kvm_check_init_and_sipi - caller has to
check for relevant transition afterward
- add write barrier after setting sipi_vector
arch/x86/kvm/lapic.c | 11 ++++++-----
arch/x86/kvm/x86.c | 15 +++++++++++++++
include/linux/kvm_host.h | 2 ++
3 files changed, 23 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 02b51dd..7986c9f 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -731,8 +731,7 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
case APIC_DM_INIT:
if (!trig_mode || level) {
result = 1;
- vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
- kvm_make_request(KVM_REQ_EVENT, vcpu);
+ kvm_make_request(KVM_REQ_INIT, vcpu);
kvm_vcpu_kick(vcpu);
} else {
apic_debug("Ignoring de-assert INIT to vcpu %d\n",
@@ -743,11 +742,13 @@ static int __apic_accept_irq(struct kvm_lapic *apic, int delivery_mode,
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) {
+ if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED ||
+ test_bit(KVM_REQ_INIT, &vcpu->requests)) {
result = 1;
vcpu->arch.sipi_vector = vector;
- vcpu->arch.mp_state = KVM_MP_STATE_SIPI_RECEIVED;
- kvm_make_request(KVM_REQ_EVENT, vcpu);
+ /* make sure sipi_vector is visible for the receiver */
+ smp_wmb();
+ kvm_make_request(KVM_REQ_SIPI, vcpu);
kvm_vcpu_kick(vcpu);
}
break;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d0cf737..0be04b9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5641,6 +5641,15 @@ static void update_eoi_exitmap(struct kvm_vcpu *vcpu)
kvm_x86_ops->load_eoi_exitmap(vcpu, eoi_exit_bitmap);
}
+static void kvm_check_init_and_sipi(struct kvm_vcpu *vcpu)
+{
+ if (kvm_check_request(KVM_REQ_INIT, vcpu))
+ vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
+ if (kvm_check_request(KVM_REQ_SIPI, vcpu) &&
+ vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED)
+ vcpu->arch.mp_state = KVM_MP_STATE_SIPI_RECEIVED;
+}
+
static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
{
int r;
@@ -5649,6 +5658,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
bool req_immediate_exit = 0;
if (vcpu->requests) {
+ kvm_check_init_and_sipi(vcpu);
+ if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
+ r = 1;
+ goto out;
+ }
if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu))
kvm_mmu_unload(vcpu);
if (kvm_check_request(KVM_REQ_MIGRATE_TIMER, vcpu))
@@ -6977,6 +6991,7 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm,
int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
{
+ kvm_check_init_and_sipi(vcpu);
return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
!vcpu->arch.apf.halted)
|| !list_empty_careful(&vcpu->async_pf.done)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 722cae7..1a191c9 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -124,6 +124,8 @@ static inline bool is_error_page(struct page *page)
#define KVM_REQ_MCLOCK_INPROGRESS 20
#define KVM_REQ_EPR_EXIT 21
#define KVM_REQ_EOIBITMAP 22
+#define KVM_REQ_INIT 23
+#define KVM_REQ_SIPI 24
#define KVM_USERSPACE_IRQ_SOURCE_ID 0
#define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1
--
1.7.3.4
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