Re: [PATCH 2/4] KVM: SVM: use NPT page attributes

[Xiao Guangrong]

On 07/08/2015 07:19 PM, Paolo Bonzini wrote:
> On 08/07/2015 07:59, Xiao Guangrong wrote:
> > On 07/07/2015 09:45 PM, Paolo Bonzini wrote:
> > > Right now, NPT page attributes are not used, and the final page
> > > attribute depends solely on gPAT (which however is not synced
> > > correctly), the guest MTRRs and the guest page attributes.
> > >
> > > However, we can do better by mimicking what is done for VMX.
> > > In the absence of PCI passthrough, the guest PAT can be ignored
> > > and the page attributes can be just WB.  If passthrough is being
> > > used, instead, keep respecting the guest PAT, and emulate the guest
> > > MTRRs through the PAT field of the nested page tables.
> > >
> > > The only snag is that WP memory cannot be emulated correctly,
> > > because Linux's default PAT setting only includes the other types.
> > >
> > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > > ---
> > >    arch/x86/kvm/svm.c | 47 ++++++++++++++++++++++++++++++++++++++++++-----
> > >    1 file changed, 42 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> > > index 602b974a60a6..0f125c1860ec 100644
> > > --- a/arch/x86/kvm/svm.c
> > > +++ b/arch/x86/kvm/svm.c
> > > @@ -1085,6 +1085,47 @@ static u64 svm_compute_tsc_offset(struct
> > > kvm_vcpu *vcpu, u64 target_tsc)
> > >        return target_tsc - tsc;
> > >    }
> > >
> > > +static void svm_set_guest_pat(struct vcpu_svm *svm, u64 *g_pat)
> > > +{
> > > +    struct kvm_vcpu *vcpu = &svm->vcpu;
> > > +
> > > +    /* Unlike Intel, AMD takes the guest's CR0.CD into account.
> >
> > I noticed this code in svm_set_cr0():
> >
> >      if (!(vcpu->kvm->arch.disabled_quirks & KVM_QUIRK_CD_NW_CLEARED))
> >          cr0 &= ~(X86_CR0_CD | X86_CR0_NW);
> >
> > gCR0.CD is hidden to CPU if KVM_QUIRK_CD_NW_CLEARED is not set and looks
> > like
> > it is the normal case after grepping Qemu code.

How about this one? I still do not know how SVM properly emulates CR0.CD? :(
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