> -Original Message-
> From: kvm-ow...@vger.kernel.org [mailto:kvm-ow...@vger.kernel.org] On
> Behalf Of Jan Kiszka
> Sent: Friday, March 28, 2014 12:15 AM
> To: Wu, Feng; pbonz...@redhat.com; g...@redhat.com; h...@zytor.com;
> kvm@vger.kernel.org
> Subject: Re: [PATCH 4/4] KVM: Disable SMAP for guests in EPT realmode and
> EPT unpaging mode
>
> On 2014-03-27 13:25, Feng Wu wrote:
> > SMAP is disabled if CPU is in non-paging mode in hardware.
> > However KVM always uses paging mode to emulate guest non-paging
> > mode with TDP. To emulate this behavior, SMAP needs to be
> > manually disabled when guest switches to non-paging mode.
> >
> > Signed-off-by: Feng Wu
> > ---
> > arch/x86/kvm/vmx.c | 10 ++
> > 1 file changed, 6 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index dcc4de3..1d37e50 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -3421,13 +3421,15 @@ static int vmx_set_cr4(struct kvm_vcpu *vcpu,
> unsigned long cr4)
> > hw_cr4 &= ~X86_CR4_PAE;
> > hw_cr4 |= X86_CR4_PSE;
> > /*
> > -* SMEP is disabled if CPU is in non-paging mode in
> > -* hardware. However KVM always uses paging mode to
> > +* SMEP/SMAP is disabled if CPU is in non-paging mode
> > +* in hardware. However KVM always uses paging mode to
> > * emulate guest non-paging mode with TDP.
> > -* To emulate this behavior, SMEP needs to be manually
> > -* disabled when guest switches to non-paging mode.
> > +* To emulate this behavior, SMEP/SMAP needs to be
> > +* manually disabled when guest switches to non-paging
> > +* mode.
> > */
> > hw_cr4 &= ~X86_CR4_SMEP;
> > + hw_cr4 &= ~X86_CR4_SMAP;
>
> Why not
>
> hw_cr4 &= ~(X86_CR4_SMEP | X86_CR4_SMAP);
>
> ?
Sure, your suggestion is cleaner, I will change it in the next version, thanks
for the comments!
>
> Jan
>
> > } else if (!(cr4 & X86_CR4_PAE)) {
> > hw_cr4 &= ~X86_CR4_PAE;
> > }
> >
>
Thanks,
Feng
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