linux-kernel - Re: [PATCH] x86: let userspace inject interrupts into the local APIC

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Message-ID: <5148C909.30103@redhat.com>
Date:	Tue, 19 Mar 2013 21:22:33 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] x86: let userspace inject interrupts into the local APIC

Il 19/03/2013 19:50, Gleb Natapov ha scritto:
> On Tue, Mar 19, 2013 at 07:39:24PM +0100, Paolo Bonzini wrote:
>> Il 19/03/2013 19:13, Gleb Natapov ha scritto:
>>>>> There is no way for userspace to inject interrupts into a VCPU's
>>>>> local APIC, which is important in order to inject INITs coming from
>>>>> the chipset.  KVM_INTERRUPT is currently disabled when the in-kernel
>>>>> local APIC is used, so we can repurpose it.  The shorthand destination
>>>>> field must contain APIC_DEST_SELF, which has a double effect: first,
>>>>> the ICR2 register is not used and the 32-bit field of KVM_INTERRUPT is
>>>>> enough; second, it ensures that the valid range of the irq field is
>>>>> distinct in the userspace-APIC and kernel-APIC cases.
>>>>>
>>> Init coming from triggering INIT# line should not be modeled as INIT coming from
>>> APIC.
>>
>> Then Jan's patch was wrong, and INIT should not have been an apic event
>> (perhaps SIPI should).
>>
> If it goes through APIC it is.

Ok, I'll extract KVM_APIC_INIT handling into a separate function and
call it synchronously from KVM_INTERRUPT, with irq = -1
(KVM_INTERRUPT_INIT, similar to PPC's values of irq).
KVM_INTERRUPT_INIT will be accessible even with in-kernel irqchip.

>>> In fact INIT cannot be send using SELF shorthand.
>>
>> Where does the SDM say that?
>>
> Table 10-3.

Yeah, table 10-6 and 10-7 here.

Paolo

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