linux-kernel - Re: [Patch v4 15/18] KVM: mmu: Add NUMA node support in struct kvm_mmu_memory

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Date:   Mon, 3 Apr 2023 15:57:17 -0700
From:   Vipin Sharma <vipinsh@...gle.com>
To:     David Matlack <dmatlack@...gle.com>
Cc:     seanjc@...gle.com, pbonzini@...hat.com, bgardon@...gle.com,
        jmattson@...gle.com, mizhang@...gle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Patch v4 15/18] KVM: mmu: Add NUMA node support in struct kvm_mmu_memory_cache{}

On Tue, Mar 28, 2023 at 4:25 PM David Matlack <dmatlack@...gle.com> wrote:
>
> On Tue, Mar 28, 2023 at 10:51 AM Vipin Sharma <vipinsh@...gle.com> wrote:
> >
> > On Thu, Mar 23, 2023 at 3:30 PM David Matlack <dmatlack@...gle.com> wrote:
> > >
> > > On Mon, Mar 06, 2023 at 02:41:24PM -0800, Vipin Sharma wrote:
> > > > +     INIT_KVM_MMU_MEMORY_CACHE(&vcpu->arch.mmu_page_cache);
> > > > +     vcpu->arch.mmu_page_cache.gfp_zero = 0;
> > >
> > > Oh MIPS is here. Why isn't MIPS covered in the previous commits?
> >
> > Because this is the patch where MIPS get impacted. MIPS doesn't
> > initialize gfp_zero, so there was no need to change the code in MIPS.
> > However, with the addition of "node" in kvm_mmu_memory_cache{} in this
> > patch, we need initialization in MIPS to (1) Set  node to NUMA_NO_NODE
> > as 0 is now a valid value, and (2) INIT_KVM_MMU_MEMORY_CACHE() will
> > set gfp_zero to __GFP_ZERO which is different than existing code in
> > MIPS to keep it 0.
> >
> > I asked MIPS maintainers in the previous version to see if GFP_ZERO
> > can be added but didn't get any response.
> > https://lore.kernel.org/lkml/CAHVum0c+17Z-RbGAFdU-xmRejDjDQ+MKOfN4XaObh2SwgWAjLg@mail.gmail.com/
>
> I see. IMO it's more logical to convert the MIPS cache to
> INIT_KVM_MMU_MEMORY_CACHE() in patch 13, along with all the other
> users of struct kvm_mmu_memory_cache. Then in patch 14, add the line
> to set gfp_zero to 0 for MIPS to preserve the existing behavior. That
> produces a very simple chain of changes:
>
> Patch 13: Convert all users of struct kvm_mmu_memory_cache to INIT()
> Patch 14: Invert the default value of kvm_mmu_memory_cache.gfp_zero
> Patch 15: Add node to kvm_mmu_memory_cache
>
>

Yeah, this looks better. I will do this.