On Thu, Mar 21, 2013 at 05:30:32AM +0000, Zhang, Yang Z wrote:
> Gleb Natapov wrote on 2013-03-21:
> > On Thu, Mar 21, 2013 at 03:42:46AM +0000, Zhang, Yang Z wrote:
> >> 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.zh...@intel.com>
> >>>>
> >>>> 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.zh...@intel.com>
> >>>> ---
> >>>> 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
> >>
> > This should be ||. Then you need to maintain in_recalculating and
> > recalculations requests may overlap. Too complex and fragile.
> It should not be too complex. How about the following logic?
>
> when make scan ioapic request:
> kvm_vcpu_scan_ioapic()
> {
> kvm_for_each_vcpu()
> in_recalculating++;
> }
>
> Then on each vcpu's request handler:
> vcpu_scan_ioapic()
> {
> in_recalculating--;
> }
>
kvm_vcpu_scan_ioapic() can be called more often then vcpu_scan_ioapic()
> And when delivering RTC interrupt:
> if(need_eoi > 0 || in_recalculating)
> return coalesced
>
>
> >
> > --
> > Gleb.
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to majord...@vger.kernel.org
> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
> Best regards,
> Yang
>
--
Gleb.
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