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KVM: fix race with level interrupts

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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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17
arch/x86/kvm/i8259.c
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@@ -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'
*/