linux-kernel - Re: [PATCH 2/3] KVM: SVM: Restore correct registers after sel

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Message-ID: <4C7FCA7A.1020809@redhat.com>
Date:	Thu, 02 Sep 2010 19:02:02 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Joerg Roedel <joerg.roedel@....com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...nel.org
Subject: Re: [PATCH 2/3] KVM: SVM: Restore correct registers after sel_cr0
 intercept emulation

  On 09/02/2010 06:29 PM, Joerg Roedel wrote:
> This patch implements restoring of the correct rip, rsp, and
> rax after the svm emulation in KVM injected a selective_cr0
> write intercept into the guest hypervisor. The problem was
> that the vmexit is emulated in the instruction emulation
> which later commits the registers right after the write-cr0
> instruction. So the l1 guest will continue to run with the
> l2 rip, rsp and rax resulting in unpredictable behavior.
>

Please post a unit test for this.

> This patch is not the final word, it is just an easy patch
> to fix the issue. The real fix will be done when the
> instruction emulator is made aware of nested virtualization.
> Until this is done this patch fixes the issue and provides
> an easy way to fix this in -stable too.

I agree.  We can probably use X86EMUL_PROPAGATE_FAULT to abort 
emulation, but looking at the code, it will take some refactoring.

-- 
error compiling committee.c: too many arguments to function

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