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KVM: ioapic: try to recover if pending_eoi goes out of range 

The RTC tracking code tracks the cardinality of rtc_status.dest_map
into rtc_status.pending_eoi.  It has some WARN_ONs that trigger if
pending_eoi ever becomes negative; however, these do not do anything
to recover, and it bad things will happen soon after they trigger.

When the next RTC interrupt is triggered, rtc_check_coalesced() will
return false, but ioapic_service will find pending_eoi != 0 and
do a BUG_ON.  To avoid this, should pending_eoi ever be nonzero,
call kvm_rtc_eoi_tracking_restore_all to recompute a correct
dest_map and pending_eoi.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-03-28 20:41:51 +01:00
parent 5678de3f15
commit 4009b2499e
1 changed files with 18 additions and 5 deletions
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23
virt/kvm/ioapic.c
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@ -97,6 +97,14 @@ static void rtc_irq_eoi_tracking_reset(struct kvm_ioapic *ioapic)
bitmap_zero(ioapic->rtc_status.dest_map, KVM_MAX_VCPUS);
}
static void kvm_rtc_eoi_tracking_restore_all(struct kvm_ioapic *ioapic);
static void rtc_status_pending_eoi_check_valid(struct kvm_ioapic *ioapic)
{
if (WARN_ON(ioapic->rtc_status.pending_eoi < 0))
kvm_rtc_eoi_tracking_restore_all(ioapic);
}
static void __rtc_irq_eoi_tracking_restore_one(struct kvm_vcpu *vcpu)
{
bool new_val, old_val;
@ -120,9 +128,8 @@ static void __rtc_irq_eoi_tracking_restore_one(struct kvm_vcpu *vcpu)
} else {
__clear_bit(vcpu->vcpu_id, ioapic->rtc_status.dest_map);
ioapic->rtc_status.pending_eoi--;
rtc_status_pending_eoi_check_valid(ioapic);
}
WARN_ON(ioapic->rtc_status.pending_eoi < 0);
}
void kvm_rtc_eoi_tracking_restore_one(struct kvm_vcpu *vcpu)
@ -149,10 +156,10 @@ static void kvm_rtc_eoi_tracking_restore_all(struct kvm_ioapic *ioapic)
static void rtc_irq_eoi(struct kvm_ioapic *ioapic, struct kvm_vcpu *vcpu)
{
if (test_and_clear_bit(vcpu->vcpu_id, ioapic->rtc_status.dest_map))
if (test_and_clear_bit(vcpu->vcpu_id, ioapic->rtc_status.dest_map)) {
--ioapic->rtc_status.pending_eoi;
WARN_ON(ioapic->rtc_status.pending_eoi < 0);
rtc_status_pending_eoi_check_valid(ioapic);
}
}
static bool rtc_irq_check_coalesced(struct kvm_ioapic *ioapic)
@ -353,6 +360,12 @@ static int ioapic_service(struct kvm_ioapic *ioapic, int irq, bool line_status)
ioapic->irr &= ~(1 << irq);
if (irq == RTC_GSI && line_status) {
/*
* pending_eoi cannot ever become negative (see
* rtc_status_pending_eoi_check_valid) and the caller
* ensures that it is only called if it is >= zero, namely
* if rtc_irq_check_coalesced returns false).
*/
BUG_ON(ioapic->rtc_status.pending_eoi != 0);
ret = kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe,
ioapic->rtc_status.dest_map);