[PATCH] KVM: x86: Convert INIT and SIPI signals into synchronously handled events

Jan Kiszka
2013-03-12T11:44:48Z

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.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---

This doesn't fix the wrong behaviour on INIT for the BSP yet. Leaving
this honor to Paolo.

I didn't try porting any INIT handling for nested on top yet but I
think it should be feasible - once we know their semantics for sure, at
least on Intel...

arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/lapic.c | 41 +++++++++++++++++++++++++++++++-------
arch/x86/kvm/lapic.h | 7 ++++++
arch/x86/kvm/x86.c | 39 ++++++++++++++++++++----------------
4 files changed, 63 insertions(+), 25 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 348d859..2d28e76 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1002,6 +1002,7 @@ int kvm_cpu_has_injectable_intr(struct kvm_vcpu *v);
int kvm_cpu_has_interrupt(struct kvm_vcpu *vcpu);
int kvm_arch_interrupt_allowed(struct kvm_vcpu *vcpu);
int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
+void kvm_vcpu_reset(struct kvm_vcpu *vcpu);

void kvm_define_shared_msr(unsigned index, u32 msr);
void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 02b51dd..4a21a6b 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -731,7 +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;
+ set_bit(KVM_APIC_INIT, &apic->pending_events);
kvm_make_request(KVM_REQ_EVENT, vcpu);
kvm_vcpu_kick(vcpu);
} else {
@@ -743,13 +743,13 @@ 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) {
- 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 +1860,31 @@ int kvm_lapic_enable_pv_eoi(struct kvm_vcpu *vcpu, u64 data)
addr);
}

+bool kvm_apic_has_events(struct kvm_vcpu *vcpu)
+{
+ return kvm_vcpu_has_lapic(vcpu) && vcpu->arch.apic->pending_events;
+}
+
+void kvm_apic_accept_events(struct kvm_vcpu *vcpu)
+{
+ struct kvm_lapic *apic = vcpu->arch.apic;
+
+ if (!kvm_vcpu_has_lapic(vcpu))
+ return;
+
+ if (test_and_clear_bit(KVM_APIC_INIT, &apic->pending_events))
+ 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) {
+ vcpu->arch.sipi_vector = apic->sipi_vector;
+ pr_debug("vcpu %d received sipi with vector # %x\n",
+ vcpu->vcpu_id, vcpu->arch.sipi_vector);
+ kvm_lapic_reset(vcpu);
+ kvm_vcpu_reset(vcpu);
+ vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
+ }
+}
+
void kvm_lapic_init(void)
{
/* do not patch jump label more than once per second */
diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
index 1676d34..ef3f4ef 100644
--- a/arch/x86/kvm/lapic.h
+++ b/arch/x86/kvm/lapic.h
@@ -5,6 +5,9 @@

#include <linux/kvm_host.h>

+#define KVM_APIC_INIT 0
+#define KVM_APIC_SIPI 1
+
struct kvm_timer {
struct hrtimer timer;
s64 period; /* unit: ns */
@@ -32,13 +35,17 @@ struct kvm_lapic {
void *regs;
gpa_t vapic_addr;
struct page *vapic_page;
+ unsigned long pending_events;
+ unsigned int sipi_vector;
};
int kvm_create_lapic(struct kvm_vcpu *vcpu);
void kvm_free_lapic(struct kvm_vcpu *vcpu);

int kvm_apic_has_interrupt(struct kvm_vcpu *vcpu);
+bool kvm_apic_has_events(struct kvm_vcpu *vcpu);
int kvm_apic_accept_pic_intr(struct kvm_vcpu *vcpu);
int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu);
+void kvm_apic_accept_events(struct kvm_vcpu *vcpu);
void kvm_lapic_reset(struct kvm_vcpu *vcpu);
u64 kvm_lapic_get_cr8(struct kvm_vcpu *vcpu);
void kvm_lapic_set_tpr(struct kvm_vcpu *vcpu, unsigned long cr8);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b891ac3..a0b8041 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -162,8 +162,6 @@ u64 __read_mostly host_xcr0;

static int emulator_fix_hypercall(struct x86_emulate_ctxt *ctxt);

-static void kvm_vcpu_reset(struct kvm_vcpu *vcpu);
-
static inline void kvm_async_pf_hash_reset(struct kvm_vcpu *vcpu)
{
int i;
@@ -5663,6 +5661,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
bool req_immediate_exit = 0;

if (vcpu->requests) {
+ kvm_apic_accept_events(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))
@@ -5847,14 +5850,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
int r;
struct kvm *kvm = vcpu->kvm;

- if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED)) {
- pr_debug("vcpu %d received sipi with vector # %x\n",
- vcpu->vcpu_id, vcpu->arch.sipi_vector);
- kvm_lapic_reset(vcpu);
- kvm_vcpu_reset(vcpu);
- vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
- }
-
vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
r = vapic_enter(vcpu);
if (r) {
@@ -5871,8 +5866,8 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx);
kvm_vcpu_block(vcpu);
vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
- if (kvm_check_request(KVM_REQ_UNHALT, vcpu))
- {
+ if (kvm_check_request(KVM_REQ_UNHALT, vcpu)) {
+ kvm_apic_accept_events(vcpu);
switch(vcpu->arch.mp_state) {
case KVM_MP_STATE_HALTED:
vcpu->arch.mp_state =
@@ -5880,7 +5875,8 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
case KVM_MP_STATE_RUNNABLE:
vcpu->arch.apf.halted = false;
break;
- case KVM_MP_STATE_SIPI_RECEIVED:
+ case KVM_MP_STATE_INIT_RECEIVED:
+ break;
default:
r = -EINTR;
break;
@@ -5901,7 +5897,8 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
++vcpu->stat.request_irq_exits;
}

- kvm_check_async_pf_completion(vcpu);
+ if (vcpu->arch.mp_state != KVM_MP_STATE_INIT_RECEIVED)
+ kvm_check_async_pf_completion(vcpu);

if (signal_pending(current)) {
r = -EINTR;
@@ -6015,6 +6012,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)

if (unlikely(vcpu->arch.mp_state == KVM_MP_STATE_UNINITIALIZED)) {
kvm_vcpu_block(vcpu);
+ kvm_apic_accept_events(vcpu);
clear_bit(KVM_REQ_UNHALT, &vcpu->requests);
r = -EAGAIN;
goto out;
@@ -6171,6 +6169,7 @@ int kvm_arch_vcpu_ioctl_get_sregs(struct kvm_vcpu *vcpu,
int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
struct kvm_mp_state *mp_state)
{
+ kvm_apic_accept_events(vcpu);
mp_state->mp_state = vcpu->arch.mp_state;
return 0;
}
@@ -6178,7 +6177,13 @@ int kvm_arch_vcpu_ioctl_get_mpstate(struct kvm_vcpu *vcpu,
int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
struct kvm_mp_state *mp_state)
{
- vcpu->arch.mp_state = mp_state->mp_state;
+ if (mp_state->mp_state == KVM_MP_STATE_SIPI_RECEIVED) {
+ if (!kvm_vcpu_has_lapic(vcpu))
+ return -EINVAL;
+ vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
+ set_bit(KVM_APIC_SIPI, &vcpu->arch.apic->pending_events);
+ } else
+ vcpu->arch.mp_state = mp_state->mp_state;
kvm_make_request(KVM_REQ_EVENT, vcpu);
return 0;
}
@@ -6515,7 +6520,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
kvm_x86_ops->vcpu_free(vcpu);
}

-static void kvm_vcpu_reset(struct kvm_vcpu *vcpu)
+void kvm_vcpu_reset(struct kvm_vcpu *vcpu)
{
atomic_set(&vcpu->arch.nmi_queued, 0);
vcpu->arch.nmi_pending = 0;
@@ -6988,7 +6993,7 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
!vcpu->arch.apf.halted)
|| !list_empty_careful(&vcpu->async_pf.done)
- || vcpu->arch.mp_state == KVM_MP_STATE_SIPI_RECEIVED
+ || kvm_apic_has_events(vcpu)
|| atomic_read(&vcpu->arch.nmi_queued) ||
(kvm_arch_interrupt_allowed(vcpu) &&
kvm_cpu_has_interrupt(vcpu));
--
1.7.3.4