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Date: Mon, 10 Oct 2016 17:11:19 +0200
From: Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>
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	<20161008072100.GJ3666@pxdev.xzpeter.org>
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Subject: Re: [Qemu-devel] [PATCH v4 6/8] intel_iommu: reject broken EIM
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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>

2016-10-08 15:21+0800, Peter Xu:
> On Wed, Oct 05, 2016 at 03:06:55PM +0200, Radim Kr=C4=8Dm=C3=A1=C5=99 w=
rote:
>=20
> [...]
>=20
>> @@ -2472,10 +2473,22 @@ static bool vtd_decide_config(IntelIOMMUState =
*s, Error **errp)
>>      }
>> =20
>>      if (s->intr_eim =3D=3D ON_OFF_AUTO_AUTO) {
>> -        s->intr_eim =3D x86_iommu->intr_supported ?
>> +        s->intr_eim =3D x86_iommu->intr_supported && kvm_irqchip_in_k=
ernel() ?
>>                                                ON_OFF_AUTO_ON : ON_OFF=
_AUTO_OFF;
>>      }
>> =20
>> +    if (s->intr_eim =3D=3D ON_OFF_AUTO_ON) {
>> +        if (kvm_irqchip_in_kernel() && !kvm_enable_x2apic()) {
>> +            error_setg(errp, "eim=3Don requires support on the KVM si=
de"
>> +                             "(X2APIC_API, first shipped in v4.7)");
>> +            return false;
>> +        }
>> +        if (!kvm_irqchip_in_kernel()) {
>> +            error_setg(errp, "eim=3Don requires accel=3Dkvm,kernel-ir=
qchip=3Dsplit");
>> +            return false;
>> +        }
>=20
> I would prefer:
>=20
>   if (kvm_irqchip_in_kernel()) {
>       if (!kvm_enable_x2apic()) {
>           error("enable x2apic failed");
>           return false;
>       }
>   } else {
>       error("need split irqchip");
>       return false;
>   }

Yeah, it looks better, thanks.

> But that's really a matter of taste. So:

I'll currently go for an implicit else: (because 4 levels of indentation
are getting helper-function worthy and it has less curly braces)

        if (!kvm_irqchip_in_kernel()) {
            error("need split irqchip");
            return false;
        }
        if (!kvm_enable_x2apic()) {
            error("enable x2apic failed");
            return false;
        }

> Reviewed-by: Peter Xu <peterx@redhat.com>

I squashed [7/8] into this patch in v5 and the second one didn't have
your r-b, so I made the change as I'd have to drop the r-b anyway.