linux-kernel - Re: [PATCH v10 033/108] KVM: x86/mmu: Allow non-zero value for non-present SPTE and removed SPTE

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Date:   Thu, 17 Nov 2022 09:58:36 -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>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...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 033/108] KVM: x86/mmu: Allow non-zero value for
 non-present SPTE and removed SPTE

On Wed, Nov 09, 2022 at 11:24:12AM +0000,
"Huang, Kai" <kai.huang@...el.com> wrote:

> > diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
> > index 2e08b2a45361..0b97a045c5f0 100644
> > --- a/arch/x86/kvm/mmu/spte.c
> > +++ b/arch/x86/kvm/mmu/spte.c
> > @@ -419,7 +419,9 @@ void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only)
> >  	shadow_dirty_mask	= has_ad_bits ? VMX_EPT_DIRTY_BIT : 0ull;
> >  	shadow_nx_mask		= 0ull;
> >  	shadow_x_mask		= VMX_EPT_EXECUTABLE_MASK;
> > -	shadow_present_mask	= has_exec_only ? 0ull : VMX_EPT_READABLE_MASK;
> > +	/* VMX_EPT_SUPPRESS_VE_BIT is needed for W or X violation. */
> > +	shadow_present_mask	=
> > +		(has_exec_only ? 0ull : VMX_EPT_READABLE_MASK) | VMX_EPT_SUPPRESS_VE_BIT;
> 
> I think this chunk can be in a separate patch since it doesn't handle fault from
> non-present to present, which is claimed by the patch title and changelog.
> 
> Or I think you need to describe handling W or X fault part in the changelog.

Ok, let me try to split that hunk.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>