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KVM: PIT: fix injection logic and count

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The PIT injection logic is problematic under the following cases:

1) If there is a higher priority vector to be delivered by the time
kvm_pit_timer_intr_post is invoked ps->inject_pending won't be set.
This opens the possibility for missing many PIT event injections (say if
guest executes hlt at this point).

2) ps->inject_pending is racy with more than two vcpus. Since there's no locking
around read/dec of pt->pending, two vcpu's can inject two interrupts for a single
pt->pending count.

Fix 1 by using an irq ack notifier: only reinject when the previous irq
has been acked. Fix 2 with appropriate locking around manipulation of
pending count and irq_ack by the injection / ack paths.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Marcelo Tosatti
2008-07-26 17:01:01 -03:00
committed by Avi Kivity
parent f52447261b
commit 3cf57fed21
3 changed files with 38 additions and 40 deletions
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7
arch/x86/kvm/i8254.h
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@@ -8,7 +8,6 @@ struct kvm_kpit_timer {
int irq;
s64 period; /* unit: ns */
s64 scheduled;
ktime_t last_update;
atomic_t pending;
};
@@ -34,8 +33,9 @@ struct kvm_kpit_state {
u32 speaker_data_on;
struct mutex lock;
struct kvm_pit *pit;
bool inject_pending; /* if inject pending interrupts */
unsigned long last_injected_time;
spinlock_t inject_lock;
unsigned long irq_ack;
struct kvm_irq_ack_notifier irq_ack_notifier;
};
struct kvm_pit {
@@ -54,7 +54,6 @@ struct kvm_pit {
#define KVM_PIT_CHANNEL_MASK 0x3
void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu);
void kvm_pit_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
void kvm_pit_load_count(struct kvm *kvm, int channel, u32 val);
struct kvm_pit *kvm_create_pit(struct kvm *kvm);
void kvm_free_pit(struct kvm *kvm);