Gleb Natapov wrote on 2013-03-20:
> On Wed, Mar 20, 2013 at 07:36:17PM +0800, Yang Zhang wrote:
>> From: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>>
>> Update RTC interrrupt's destination vcpu map when ioapic entry of RTC
>> or apic register (id, ldr, dfr) is changed.
>>
>> Signed-off-by: Yang Zhang <yang.z.zhang@xxxxxxxxx>
>> ---
>> virt/kvm/ioapic.c | 9 +++++++--
>> 1 files changed, 7 insertions(+), 2 deletions(-)
>> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
>> index ddf9414..91b4c08 100644
>> --- a/virt/kvm/ioapic.c
>> +++ b/virt/kvm/ioapic.c
>> @@ -121,6 +121,7 @@ void kvm_ioapic_scan_entry(struct kvm_vcpu *vcpu,
>> { struct kvm_ioapic *ioapic = vcpu->kvm->arch.vioapic; union
>> kvm_ioapic_redirect_entry *e; + unsigned long *rtc_map =
>> ioapic->rtc_status.vcpu_map; struct kvm_lapic_irq irqe; int index;
>> @@ -130,15 +131,19 @@ void kvm_ioapic_scan_entry(struct kvm_vcpu *vcpu,
>> if (!e->fields.mask &&
>> (e->fields.trig_mode == IOAPIC_LEVEL_TRIG ||
>> kvm_irq_has_notifier(ioapic->kvm, KVM_IRQCHIP_IOAPIC,
>> - index))) {
>> + index) || index == 8)) {
>> irqe.dest_id = e->fields.dest_id;
>> irqe.vector = e->fields.vector;
>> irqe.dest_mode = e->fields.dest_mode;
>> irqe.shorthand = 0;
>>
>> if (kvm_apic_match_dest(vcpu, NULL, irqe.shorthand,
>> - irqe.dest_id, irqe.dest_mode))
>> + irqe.dest_id, irqe.dest_mode)) {
>> __set_bit(irqe.vector, eoi_exit_bitmap);
>> + if (index == 8)
>> + __set_bit(vcpu->vcpu_id, rtc_map);
>> + } else if (index == 8)
>> + __clear_bit(vcpu->vcpu_id, rtc_map);
> rtc_map bitmap is accessed from different vcpus simultaneously so access
> has to be atomic. We also have a race:
>
> vcpu0 iothread
> ioapic config changes
> request scan ioapic
> inject rtc interrupt
> use old vcpu mask
> scan_ioapic()
> recalculate vcpu mask
>
> So this approach (suggested by me :() will not work.
>
> Need to think about it some more. May be your idea of building a bitmap
> while injecting the interrupt is the way to go indeed: pass a pointer to
> a bitmap to kvm_irq_delivery_to_apic() and build it there. Pass NULL
> pointer if caller does not need to track vcpus.
Or, we can block inject rtc interrupt during recalculate vcpu map.
if(need_eoi > 0 && in_recalculating)
return coalesced
Best regards,
Yang
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