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

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Message-ID: <20130319185025.GM19292@redhat.com>
Date:	Tue, 19 Mar 2013 20:50:26 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] x86: let userspace inject interrupts into the local APIC

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. Also the problem with reusing KVM_INTERRUPT is
that it is synchronous interface but INIT# is asynchronous. Shouldn't be a big
deal though.

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

--
			Gleb.
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