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Date: Fri, 30 Sep 2016 15:55:56 +0200
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 7/7] intel-iommu: keep buggy EIM enabled
 in 2.7 machine type
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To: Peter Xu <peterx@redhat.com>
Cc: qemu-devel@nongnu.org, Igor Mammedov <imammedo@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>, Eduardo Habkost <ehabkost@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>

2016-09-30 13:40+0800, Peter Xu:
> On Thu, Sep 29, 2016 at 01:23:29PM +0200, Radim Kr=C4=8Dm=C3=A1=C5=99 w=
rote:
>=20
> [...]
>=20
>> @@ -2481,11 +2482,14 @@ static void vtd_realize(DeviceState *dev, Erro=
r **errp)
>>      if (s->intr_eim =3D=3D ON_OFF_AUTO_AUTO && !x86_iommu->intr_suppo=
rted) {
>>          s->intr_eim =3D ON_OFF_AUTO_OFF;
>>      }
>> +    if (s->intr_eim =3D=3D ON_OFF_AUTO_AUTO && pcmc->buggy_intel_iomm=
u_eim) {
>> +        s->intr_eim =3D ON_OFF_AUTO_ON;
>> +    }
>>      if (s->intr_eim =3D=3D ON_OFF_AUTO_AUTO) {
>>          s->intr_eim =3D kvm_irqchip_in_kernel() ? ON_OFF_AUTO_ON
>>                                                : ON_OFF_AUTO_OFF;
>>      }
>> -    if (s->intr_eim =3D=3D ON_OFF_AUTO_ON) {
>> +    if (s->intr_eim =3D=3D ON_OFF_AUTO_ON && !pcmc->buggy_intel_iommu=
_eim) {
>>          if (kvm_irqchip_in_kernel() && !kvm_enable_x2apic()) {
>>              error_report("intel-iommu,eim=3Don requires support on th=
e KVM side "
>>                           "(X2APIC_API, first shipped in v4.7).");
>=20
> No matter how we would treat this patch, I see that we are stacking up
> if clauses here. So IMHO maybe it's time to award EIM a new routine:
>=20
>   int vtd_eim_detect(IntelIOMMUState *, Error **errp);
>=20
> And squash all these conditions in. Then in vtd_realize():
>=20
>   if (vtd_eim_detect(s, errp)) {
>       return;
>   }

Yeah, thanks.