Re: KVM: nSVM: Check for NRIPS support before updating control field

[Luis Henriques <luis.henriques@canonical.com>]

On Mon, Jun 29, 2015 at 04:22:42PM -0400, Bandan Das wrote:
> Greg KH <gregkh@linuxfoundation.org> writes:
> 
> > On Mon, Jun 29, 2015 at 03:18:51PM -0400, Bandan Das wrote:
> >> 
> >> Commit f104765b4f81fd74d69e0eb161e89096deade2db upstream.
> >> 
> >> This causes the L1 guest to crash when running a nested guest
> >> with an AMD processor that doesn't support NRIPS.
> >> 
> >> If hardware doesn't support DecodeAssist - a feature that provides
> >> more information about the intercept in the VMCB, KVM decodes the
> >> instruction and then updates the next_rip vmcb control field.
> >> However, NRIP support itself depends on cpuid Fn8000_000A_EDX[NRIPS].
> >> Since skip_emulated_instruction() doesn't verify nrip support
> >> before accepting control.next_rip as valid, avoid writing this
> >> field if support isn't present.
> >> 
> >> Signed-off-by: Bandan Das <bsd@redhat.com>
> >> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> >> ---
> >>  arch/x86/kvm/svm.c | 8 ++++++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > What stable kernel trees do you want this applied to?
> 
> Sorry, I missed that part. I believe this bug is present
> since commit cfec82cb7d3 which makes it applicable to
> #3.0+
> 

Thanks, queuing it for the 3.16 kernel.

Cheers,
--
Lu�s

> Bandan
> > thanks,
> >
> > greg k-h
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