linux-kernel - Re: [PATCH v5 7/7] KVM: x86/mmu: explicitly check nx_hugepage in disallowed_hugepage

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Date:   Mon, 10 Oct 2022 16:31:50 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Yan Zhao <yan.y.zhao@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mingwei Zhang <mizhang@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: Re: [PATCH v5 7/7] KVM: x86/mmu: explicitly check nx_hugepage in
 disallowed_hugepage_adjust()

On Mon, Oct 10, 2022, Yan Zhao wrote:
> On Fri, Sep 30, 2022 at 11:48:54PM +0000, Sean Christopherson wrote:
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 54005b7f1499..688beed3a41e 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -3110,6 +3110,11 @@ void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_
> >  	    cur_level == fault->goal_level &&
> >  	    is_shadow_present_pte(spte) &&
> >  	    !is_large_pte(spte)) {
> > +		u64 page_mask;
> > +
> > +		if (!spte_to_child_sp(spte)->nx_huge_page_disallowed)
> > +			return;
> Merge this "if" with the upper level "if" ?

Ya, good call.  The separate check is no longer necessary now that the superfluous
smp_rmb() is gone.  That'll minimize the diff to.