2016-09-14 23:48+0200, Paolo Bonzini:
> When userspace sends KVM_SET_LAPIC, KVM schedules a check between
> the vCPU's IRR and ISR and the IOAPIC redirection table, in order
> to re-establish the IOAPIC's dest_map (the list of CPUs servicing
> the real-time clock interrupt with the corresponding vectors).
>
> However, __rtc_irq_eoi_tracking_restore_one was forgetting to
> set dest_map->vectors. Because of this, the IOAPIC did not process
> the real-time clock interrupt EOI, ioapic->rtc_status.pending_eoi
> got stuck at a non-zero value, and further RTC interrupts were
> reported to userspace as coalesced.
>
> Fixes: 9e4aabe2bb3454c83dac8139cf9974503ee044db
> Fixes: 4d99ba898dd0c521ca6cdfdde55c9b58aea3cb3d
> Cc: Joerg Roedel <jroedel@xxxxxxx>
> Cc: David Gilbert <dgilbert@xxxxxxxxxx>
> Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
Nice catch,
Reviewed-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
(It is sad that the RTC EOI tracking exists ...)
> arch/x86/kvm/ioapic.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
> index 5f42d038fcb4..c7220ba94aa7 100644
> --- a/arch/x86/kvm/ioapic.c
> +++ b/arch/x86/kvm/ioapic.c
> @@ -109,6 +109,7 @@ static void __rtc_irq_eoi_tracking_restore_one(struct kvm_vcpu *vcpu)
> {
> bool new_val, old_val;
> struct kvm_ioapic *ioapic = vcpu->kvm->arch.vioapic;
> + struct dest_map *dest_map = &ioapic->rtc_status.dest_map;
> union kvm_ioapic_redirect_entry *e;
>
> e = &ioapic->redirtbl[RTC_GSI];
> @@ -117,16 +118,17 @@ static void __rtc_irq_eoi_tracking_restore_one(struct kvm_vcpu *vcpu)
> return;
>
> new_val = kvm_apic_pending_eoi(vcpu, e->fields.vector);
> - old_val = test_bit(vcpu->vcpu_id, ioapic->rtc_status.dest_map.map);
> + old_val = test_bit(vcpu->vcpu_id, dest_map->map);
>
> if (new_val == old_val)
> return;
>
> if (new_val) {
> - __set_bit(vcpu->vcpu_id, ioapic->rtc_status.dest_map.map);
> + __set_bit(vcpu->vcpu_id, dest_map->map);
> + dest_map->vectors[vcpu->vcpu_id] = e->fields.vector;
> ioapic->rtc_status.pending_eoi++;
> } else {
> - __clear_bit(vcpu->vcpu_id, ioapic->rtc_status.dest_map.map);
> + __clear_bit(vcpu->vcpu_id, dest_map->map);
> ioapic->rtc_status.pending_eoi--;
> rtc_status_pending_eoi_check_valid(ioapic);
> }
> --
> 1.8.3.1
>
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