linux-kernel - Re: [PATCH v10 032/108] KVM: x86/mmu: Make sync_page not use hard-coded 0 as the initial SPTE value

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Message-ID: <20221117175546.GH2350331@ls.amr.corp.intel.com>
Date:   Thu, 17 Nov 2022 09:55:46 -0800
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     "Huang, Kai" <kai.huang@...el.com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Shahar, Sagi" <sagis@...gle.com>,
        "Aktas, Erdem" <erdemaktas@...gle.com>,
        "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>,
        "dmatlack@...gle.com" <dmatlack@...gle.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
Subject: Re: [PATCH v10 032/108] KVM: x86/mmu: Make sync_page not use
 hard-coded 0 as the initial SPTE value

On Wed, Nov 09, 2022 at 11:24:44AM +0000,
"Huang, Kai" <kai.huang@...el.com> wrote:

> On Sat, 2022-10-29 at 23:22 -0700, isaku.yamahata@...el.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@...el.com>
> > 
> > FNAME(sync_page) in arch/x86/kvm/mmu/paging_tmpl.h assumes that the initial
> > shadow page table entry (SPTE) is zero.  Remove the assumption by using
> > SHADOW_NONPRESENT_VALUE that will be updated from 0 to non-zero value.
> > 
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> > ---
> >  arch/x86/kvm/mmu/paging_tmpl.h | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> > index 5ab5f94dcb6f..6db3f2b5563a 100644
> > --- a/arch/x86/kvm/mmu/paging_tmpl.h
> > +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> > @@ -1036,7 +1036,8 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
> >  		gpa_t pte_gpa;
> >  		gfn_t gfn;
> >  
> > -		if (!sp->spt[i])
> > +		/* spt[i] has initial value of shadow page table allocation */
> > +		if (sp->spt[i] == SHADOW_NONPRESENT_VALUE)
> >  			continue;
> >  
> >  		pte_gpa = first_pte_gpa + i * sizeof(pt_element_t);
> 
> I think this patch can be merged to previous one?  Looks there's no good reason
> to keep it as standalone.

Yes, will squash it.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>