On Thu, Apr 11, 2013 at 01:03:30AM +0000, Zhang, Yang Z wrote:
> Gleb Natapov wrote on 2013-04-10:
> > On Wed, Apr 10, 2013 at 09:22:50PM +0800, Yang Zhang wrote:
> >> From: Yang Zhang <[email protected]>
> >>
> >> The follwoing patches are adding the Posted Interrupt supporting to KVM:
> >> The first patch enables the feature 'acknowledge interrupt on vmexit'.Since
> >> it is required by Posted interrupt, we need to enable it firstly.
> >>
> >> And the subsequent patches are adding the posted interrupt supporting:
> >> Posted Interrupt allows APIC interrupts to inject into guest directly
> >> without any vmexit.
> >>
> >> - When delivering a interrupt to guest, if target vcpu is running,
> >> update Posted-interrupt requests bitmap and send a notification event
> >> to the vcpu. Then the vcpu will handle this interrupt automatically,
> >> without any software involvemnt.
> >> - If target vcpu is not running or there already a notification event
> >> pending in the vcpu, do nothing. The interrupt will be handled by
> >> next vm entry
> >> Changes from v8 to v9:
> >> * Add tracing in PI case when deliver interrupt.
> >> * Scan ioapic when updating SPIV register.
> > Do not see it at the patch series. Have I missed it?
> The change is in forth patch:
>
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 6796218..4ccdc94 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -134,11 +134,7 @@ static inline void apic_set_spiv(struct kvm_lapic *apic,
> u32 val)
> static_key_slow_inc(&apic_sw_disabled.key);
> }
> apic_set_reg(apic, APIC_SPIV, val);
> -}
> -
> -static inline int apic_enabled(struct kvm_lapic *apic)
> -{
> - return kvm_apic_sw_enabled(apic) && kvm_apic_hw_enabled(apic);
> + kvm_make_request(KVM_REQ_SCAN_IOAPIC, apic->vcpu);
> }
>
OK, see it now. Thanks.
> As you mentioned, since it will call apic_enabled() to check whether apic is
> enabled in vcpu_scan_ioapic. So we must ensure rescan ioapic when apic state
> changed.
> And I found recalculate_apic_map() doesn't track the enable/disable apic by
> software approach. So make_scan_ioapic_request in recalculate_apic_map() is
> not enough.
> We also should force rescan ioapic when apic state is changed via software
> approach(update spiv reg).
>
10.4.7.2 Local APIC State After It Has Been Software Disabled says:
Pending interrupts in the IRR and ISR registers are held and require
masking or handling by the CPU.
My understanding is that we should treat software disabled APIC as a
valid target for an interrupt. vcpu_scan_ioapic() should check
kvm_apic_hw_enabled() only.
--
Gleb.
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