Re: [PATCH 1/3] KVM: MMU: fix smap permission check

[Xiao Guangrong]

On 05/07/2015 05:32 PM, Paolo Bonzini wrote:
> On 07/05/2015 10:20, Xiao Guangrong wrote:
> > Current permission check assumes that RSVD bit in PFEC is always zero,
> > however, it is not true since MMIO #PF will use it to quickly identify
> > MMIO access
> >
> > Fix it by clearing the bit if walking guest page table is needed
> >
> > Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> > ---
> >   arch/x86/kvm/mmu.h         | 2 ++
> >   arch/x86/kvm/paging_tmpl.h | 7 +++++++
> >   2 files changed, 9 insertions(+)
> >
> > diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> > index c7d6563..06eb2fc 100644
> > --- a/arch/x86/kvm/mmu.h
> > +++ b/arch/x86/kvm/mmu.h
> > @@ -166,6 +166,8 @@ static inline bool permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> >   	int index = (pfec >> 1) +
> >   		    (smap >> (X86_EFLAGS_AC_BIT - PFERR_RSVD_BIT + 1));
> >
> > +	WARN_ON(pfec & PFERR_RSVD_MASK);
> > +
> >   	return (mmu->permissions[index] >> pte_access) & 1;
> >   }
> >
> > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> > index fd49c86..6e6d115 100644
> > --- a/arch/x86/kvm/paging_tmpl.h
> > +++ b/arch/x86/kvm/paging_tmpl.h
> > @@ -718,6 +718,13 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
> >   					      mmu_is_nested(vcpu));
> >   		if (likely(r != RET_MMIO_PF_INVALID))
> >   			return r;
> > +
> > +		/*
> > +		 * page fault with PFEC.RSVD  = 1 is caused by shadow
> > +		 * page fault, should not be used to walk guest page
> > +		 * table.
> > +		 */
> > +		error_code &= ~PFERR_RSVD_MASK;
> >   	};
> >
> >   	r = mmu_topup_memory_caches(vcpu);
>
> Applied.
>
> For the other patches I'm waiting for an answer re. kvm_mmu_pte_write.

Sure. Actually, i noticed these bugs when i was reviewing your patches,
will continue to review soon. :)
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