linux-kernel - Re: [PATCH 7/8] KVM: x86: Allow marking an exception as reinjected

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Message-ID: <20100423142702.GH31537@amd.com>
Date:	Fri, 23 Apr 2010 16:27:03 +0200
From:	Joerg Roedel <joerg.roedel@....com>
To:	Alexander Graf <agraf@...e.de>
CC:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/8] KVM: x86: Allow marking an exception as reinjected

On Fri, Apr 23, 2010 at 03:57:32PM +0200, Alexander Graf wrote:
> 
> On 22.04.2010, at 12:33, Joerg Roedel wrote:
> 
> > This patch adds logic to kvm/x86 which allows to mark an
> > injected exception as reinjected. This allows to remove an
> > ugly hack from svm_complete_interrupts that prevented
> > exceptions from being reinjected at all in the nested case.
> > The hack was necessary because an reinjected exception into
> > the nested guest could cause a nested vmexit emulation. But
> > reinjected exceptions must not intercept. The downside of
> > the hack is that a exception that in injected could get
> > lost.
> > This patch fixes the problem and puts the code for it into
> > generic x86 files because. Nested-VMX will likely have the
> > same problem and could reuse the code.
> 
> So we always handle the reinjection from KVM code? Shouldn't the l1
> hypervisor do this?

No. We only have the problem if we need to handle a nested intercept on
the host level instead of reinjecting it. So the nested hypervisor
couldn't be involved in the reinjection.

	Joerg


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