linux-kernel - Re: [PATCH v7 5/8] KVM: x86/mmu: Don't pass FOLL_GET to __kvm_follow

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Date:   Wed, 5 Jul 2023 22:17:42 +0800
From:   Yu Zhang <yu.c.zhang@...ux.intel.com>
To:     David Stevens <stevensd@...omium.org>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Marc Zyngier <maz@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Peter Xu <peterx@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v7 5/8] KVM: x86/mmu: Don't pass FOLL_GET to
 __kvm_follow_pfn

> > @@ -883,7 +884,7 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> >   */
> >  static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int i)
> >  {
> > -	bool host_writable;
> > +	bool host_writable, is_refcounted;
> >  	gpa_t first_pte_gpa;
> >  	u64 *sptep, spte;
> >  	struct kvm_memory_slot *slot;
> > @@ -940,10 +941,12 @@ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int
> >  	sptep = &sp->spt[i];
> >  	spte = *sptep;
> >  	host_writable = spte & shadow_host_writable_mask;
> > +	// TODO: is this correct?
> > +	is_refcounted = spte & SPTE_MMU_PAGE_REFCOUNTED;
> >  	slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
> >  	make_spte(vcpu, sp, slot, pte_access, gfn,
> >  		  spte_to_pfn(spte), spte, true, false,
> > -		  host_writable, &spte);
> > +		  host_writable, is_refcounted, &spte);
> 
> Could we restrict that a non-refcounted page shall not be used as shadow page?

Oh, sorry. It's not about shadow page. It's about guest page being
mapped as not refcounted. Silly me...

B.R.
Yu