linux-kernel - Re: [PATCH v3 12/14] KVM: x86: add a flag to disable KVM x2apic broadcast quirk

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Message-ID: <20160713145249.GC22438@potion>
Date:	Wed, 13 Jul 2016 16:52:49 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	"Lan, Tianyu" <tianyu.lan@...el.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Jan Kiszka <jan.kiszka@....de>, Peter Xu <peterx@...hat.com>,
	Yang Zhang <yang.zhang.wz@...il.com>
Subject: Re: [PATCH v3 12/14] KVM: x86: add a flag to disable KVM x2apic
 broadcast quirk

2016-07-13 12:15+0200, Paolo Bonzini:
> On 12/07/2016 22:09, Radim Krčmář wrote:
>> +static bool kvm_apic_map_need_slowpath(struct kvm *kvm, struct kvm_lapic **src,
>> +		struct kvm_lapic_irq *irq, struct kvm_apic_map *map)
>> +{
>> +	if (!map)
>> +		return true;
>> +
>> +	if (kvm->arch.x2apic_broadcast_quirk_disabled) {
>> +		if ((irq->dest_id == APIC_BROADCAST &&
>> +				map->mode != KVM_APIC_MODE_X2APIC))
>> +			return true;
>> +		if (irq->dest_id == X2APIC_BROADCAST)
>> +			return true;
>> +	} else {
>> +		bool x2apic_ipi = src && *src && apic_x2apic_mode(*src);
>> +		if (irq->dest_id == (x2apic_ipi ?
>> +		                     X2APIC_BROADCAST : APIC_BROADCAST))
>> +			return true;
>> +	}
>> +
>> +	return false;
>> +}
> 
> This isn't the only case where you go through the slowpath.  What about
> renaming to kvm_apic_dest_is_broadcast?

Yeah, sorry.  I have a patch that adds a check for 0xff in flat lapic
mode (can be handled in the fast path) and used the same name even
before the check ...