Gleb Natapov wrote on 2013-04-11:
> 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 <yang.z.zhang@xxxxxxxxx>
>>>>
>>>> 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.
Indeed. kvm_apic_hw_enabled() is the right one.
Best regards,
Yang
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