linux-kernel - Re: [PATCH 1/2] KVM: SVM: Fix NMI path when NMI happens in guest mode

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Message-ID: <20110114133602.GC23914@amd.com>
Date:	Fri, 14 Jan 2011 14:36:02 +0100
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Avi Kivity <avi@...hat.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...nel.org" <stable@...nel.org>
Subject: Re: [PATCH 1/2] KVM: SVM: Fix NMI path when NMI happens in guest
 mode

On Thu, Jan 13, 2011 at 02:27:00PM -0500, Avi Kivity wrote:
> On 01/13/2011 05:51 PM, Roedel, Joerg wrote:
> > I also had a look at entry_64.S. The save_paranoid could not be the
> > cause because MSR_GS_BASE is already negative at this point. But the
> > re-schedule condition check at the end of the NMI handler code could
> > also not be the cause because the NMI happens while preemption (and
> > interrupts) are disabled (a re-schedule should also trigger
> > preempt-notifiers and restore KERNEL_GS_BASE).
> >
> 
> I have it:

Cool, good catch. Thanks :)

The only use of load_gs_index in svm is the vcpu_put function. It is
sufficient to just swap the KERNEL_GS_BASE wrmsr and the load_gs_index
function calls in there to be safe.

	Joerg

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