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

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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@xxxxxxxxxx>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
>  arch/x86/kvm/svm.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

What stable kernel trees do you want this applied to?

thanks,

greg k-h
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