linux-kernel - Re: [Patch v4 16/18] KVM: x86/mmu: Allocate numa aware page tables during page fault

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Date:   Mon, 3 Apr 2023 15:54:27 -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 16/18] KVM: x86/mmu: Allocate numa aware page tables
 during page fault

On Wed, Mar 29, 2023 at 12:04 PM David Matlack <dmatlack@...gle.com> wrote:
>
> On Tue, Mar 28, 2023 at 05:21:29PM -0700, David Matlack wrote:
> > On Mon, Mar 06, 2023 at 02:41:25PM -0800, Vipin Sharma wrote:
> > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > > index 64de083cd6b9..77d3aa368e5e 100644
> > > --- a/arch/x86/include/asm/kvm_host.h
> > > +++ b/arch/x86/include/asm/kvm_host.h
> > > @@ -787,7 +787,7 @@ struct kvm_vcpu_arch {
> > >     struct kvm_mmu *walk_mmu;
> > >
> > >     struct kvm_mmu_memory_cache mmu_pte_list_desc_cache;
> > > -   struct kvm_mmu_memory_cache mmu_shadow_page_cache;
> > > +   struct kvm_mmu_memory_cache mmu_shadow_page_cache[MAX_NUMNODES];
> >
> > I think we need an abstraction for a NUMA-aware mmu cache, since there
> > is more than one by the end of this series.
> >
> > e.g. A wrapper struct (struct kvm_mmu_numa_memory_cache) or make
> > NUMA-awareness an optional feature within kvm_mmu_memory_cache, plus
> > common helper functions for operations like initializing, topping-up,
> > and freeing.
> >
> > I have some ideas I want to try but I ran out of time today.
>
> Something like this (compile test only, applies on top of this series):
>

It looks good to me. I was not sure in the first place if having a new
struct will be acceptable. Below abstraction looks good to me, I will
update my patches accordingly in the next version.

Thanks