linux-kernel - Re: [PATCH v5 3/7] KVM: x86/mmu: Recover TDP MMU NX huge pages using MMU read lock

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Message-ID: <CALzav=e0cUTMzox7p3AU37wAFRrOXEDdU24eqe6DX+UZYt9FeQ@mail.gmail.com>
Date: Mon, 28 Jul 2025 11:17:08 -0700
From: David Matlack <dmatlack@...gle.com>
To: James Houghton <jthoughton@...gle.com>
Cc: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Vipin Sharma <vipinsh@...gle.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/7] KVM: x86/mmu: Recover TDP MMU NX huge pages using
 MMU read lock

On Mon, Jul 28, 2025 at 11:08 AM James Houghton <jthoughton@...gle.com> wrote:
> On Wed, Jul 23, 2025 at 1:35 PM Sean Christopherson <seanjc@...gle.com> wrote:
> > > @@ -7559,8 +7590,17 @@ static void kvm_recover_nx_huge_pages(struct kvm *kvm,
> > >       rcu_read_lock();
> > >
> > >       for ( ; to_zap; --to_zap) {
> > > -             if (list_empty(nx_huge_pages))
> > > +#ifdef CONFIG_X86_64
> >
> > These #ifdefs still make me sad, but I also still think they're the least awful
> > solution.  And hopefully we will jettison 32-bit sooner than later :-)
>
> Yeah I couldn't come up with anything better. :(

Could we just move the definition of tdp_mmu_pages_lock outside of
CONFIG_X86_64? The only downside I can think of is slightly larger kvm
structs for 32-bit builds.