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KVM: fix race with level interrupts 

When more than 1 source id is in use for the same GSI, we have the
following race related to handling irq_states race:

CPU 0 clears bit 0. CPU 0 read irq_state as 0. CPU 1 sets level to 1.
CPU 1 calls kvm_ioapic_set_irq(1). CPU 0 calls kvm_ioapic_set_irq(0).
Now ioapic thinks the level is 0 but irq_state is not 0.

Fix by performing all irq_states bitmap handling under pic/ioapic lock.
This also removes the need for atomics with irq_states handling.

Reported-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2012-07-19 13:45:20 +03:00 committed by Marcelo Tosatti
parent d63d3e6217
commit 1a577b7247
5 changed files with 51 additions and 35 deletions
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15
arch/x86/include/asm/kvm_host.h
View File

@ -816,7 +816,20 @@ int kvm_read_guest_page_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
void kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault);
bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);
int kvm_pic_set_irq(void *opaque, int irq, int level);
static inline int __kvm_irq_line_state(unsigned long *irq_state,
int irq_source_id, int level)
{
/* Logical OR for level trig interrupt */
if (level)
__set_bit(irq_source_id, irq_state);
else
__clear_bit(irq_source_id, irq_state);
return !!(*irq_state);
}
int kvm_pic_set_irq(struct kvm_pic *pic, int irq, int irq_source_id, int level);
void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id);
void kvm_inject_nmi(struct kvm_vcpu *vcpu);

17
arch/x86/kvm/i8259.c
View File

@ -188,14 +188,15 @@ void kvm_pic_update_irq(struct kvm_pic *s)
pic_unlock(s);
}
int kvm_pic_set_irq(void *opaque, int irq, int level)
int kvm_pic_set_irq(struct kvm_pic *s, int irq, int irq_source_id, int level)
{
struct kvm_pic *s = opaque;
int ret = -1;
pic_lock(s);
if (irq >= 0 && irq < PIC_NUM_PINS) {
ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, level);
int irq_level = __kvm_irq_line_state(&s->irq_states[irq],
irq_source_id, level);
ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, irq_level);
pic_update_irq(s);
trace_kvm_pic_set_irq(irq >> 3, irq & 7, s->pics[irq >> 3].elcr,
s->pics[irq >> 3].imr, ret == 0);
@ -205,6 +206,16 @@ int kvm_pic_set_irq(void *opaque, int irq, int level)
return ret;
}
void kvm_pic_clear_all(struct kvm_pic *s, int irq_source_id)
{
int i;
pic_lock(s);
for (i = 0; i < PIC_NUM_PINS; i++)
__clear_bit(irq_source_id, &s->irq_states[i]);
pic_unlock(s);
}
/*
* acknowledge interrupt 'irq'
*/

19
virt/kvm/ioapic.c
View File

@ -191,7 +191,8 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
return kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe);
}
int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,
int level)
{
u32 old_irr;
u32 mask = 1 << irq;
@ -201,9 +202,11 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
spin_lock(&ioapic->lock);
old_irr = ioapic->irr;
if (irq >= 0 && irq < IOAPIC_NUM_PINS) {
int irq_level = __kvm_irq_line_state(&ioapic->irq_states[irq],
irq_source_id, level);
entry = ioapic->redirtbl[irq];
level ^= entry.fields.polarity;
if (!level)
irq_level ^= entry.fields.polarity;
if (!irq_level)
ioapic->irr &= ~mask;
else {
int edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);
@ -221,6 +224,16 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
return ret;
}
void kvm_ioapic_clear_all(struct kvm_ioapic *ioapic, int irq_source_id)
{
int i;
spin_lock(&ioapic->lock);
for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++)
__clear_bit(irq_source_id, &ioapic->irq_states[i]);
spin_unlock(&ioapic->lock);
}
static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,
int trigger_mode)
{

4
virt/kvm/ioapic.h
View File

@ -74,7 +74,9 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode);
bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector);
int kvm_ioapic_init(struct kvm *kvm);
void kvm_ioapic_destroy(struct kvm *kvm);
int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,
int level);
void kvm_ioapic_clear_all(struct kvm_ioapic *ioapic, int irq_source_id);
void kvm_ioapic_reset(struct kvm_ioapic *ioapic);
int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
struct kvm_lapic_irq *irq);

31
virt/kvm/irq_comm.c
View File

@ -33,26 +33,12 @@
#include "ioapic.h"
static inline int kvm_irq_line_state(unsigned long *irq_state,
int irq_source_id, int level)
{
/* Logical OR for level trig interrupt */
if (level)
set_bit(irq_source_id, irq_state);
else
clear_bit(irq_source_id, irq_state);
return !!(*irq_state);
}
static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,
struct kvm *kvm, int irq_source_id, int level)
{
#ifdef CONFIG_X86
struct kvm_pic *pic = pic_irqchip(kvm);
level = kvm_irq_line_state(&pic->irq_states[e->irqchip.pin],
irq_source_id, level);
return kvm_pic_set_irq(pic, e->irqchip.pin, level);
return kvm_pic_set_irq(pic, e->irqchip.pin, irq_source_id, level);
#else
return -1;
#endif
@ -62,10 +48,7 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e,
struct kvm *kvm, int irq_source_id, int level)
{
struct kvm_ioapic *ioapic = kvm->arch.vioapic;
level = kvm_irq_line_state(&ioapic->irq_states[e->irqchip.pin],
irq_source_id, level);
return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, level);
return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, irq_source_id, level);
}
inline static bool kvm_is_dm_lowest_prio(struct kvm_lapic_irq *irq)
@ -249,8 +232,6 @@ unlock:
void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)
{
int i;
ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID);
mutex_lock(&kvm->irq_lock);
@ -263,14 +244,10 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)
if (!irqchip_in_kernel(kvm))
goto unlock;
for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++) {
clear_bit(irq_source_id, &kvm->arch.vioapic->irq_states[i]);
if (i >= 16)
continue;
kvm_ioapic_clear_all(kvm->arch.vioapic, irq_source_id);
#ifdef CONFIG_X86
clear_bit(irq_source_id, &pic_irqchip(kvm)->irq_states[i]);
kvm_pic_clear_all(pic_irqchip(kvm), irq_source_id);
#endif
}
unlock:
mutex_unlock(&kvm->irq_lock);
}