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

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Message-Id: <3731206E-63C9-4A5C-9B20-E31D7559CEAF@suse.de>
Date:	Fri, 23 Apr 2010 16:41:41 +0200
From:	Alexander Graf <agraf@...e.de>
To:	Joerg Roedel <joerg.roedel@....com>
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 23.04.2010, at 16:27, Joerg Roedel wrote:

> 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.

Hrm, makes sense. Not pretty.


Alex

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