linux-kernel - Re: [PATCH 1/5] KVM: Add gfp_custom flag in struct kvm_mmu_memory

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Date:   Mon, 18 Jul 2022 09:34:15 +0530
From:   Anup Patel <anup@...infault.org>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Anup Patel <apatel@...tanamicro.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Alistair Francis <Alistair.Francis@....com>,
        KVM General <kvm@...r.kernel.org>,
        "open list:KERNEL VIRTUAL MACHINE FOR RISC-V (KVM/riscv)" 
        <kvm-riscv@...ts.infradead.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>,
        Atish Patra <atishp@...shpatra.org>
Subject: Re: [PATCH 1/5] KVM: Add gfp_custom flag in struct kvm_mmu_memory_cache

Hi Paolo,

On Wed, Jul 13, 2022 at 6:57 AM Atish Patra <atishp@...shpatra.org> wrote:
>
> On Thu, Jul 7, 2022 at 7:53 AM Anup Patel <apatel@...tanamicro.com> wrote:
> >
> > The kvm_mmu_topup_memory_cache() always uses GFP_KERNEL_ACCOUNT for
> > memory allocation which prevents it's use in atomic context. To address
> > this limitation of kvm_mmu_topup_memory_cache(), we add gfp_custom flag
> > in struct kvm_mmu_memory_cache. When the gfp_custom flag is set to some
> > GFP_xyz flags, the kvm_mmu_topup_memory_cache() will use that instead of
> > GFP_KERNEL_ACCOUNT.
> >
> > Signed-off-by: Anup Patel <apatel@...tanamicro.com>
> > ---
> >  include/linux/kvm_types.h | 1 +
> >  virt/kvm/kvm_main.c       | 4 +++-
> >  2 files changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/linux/kvm_types.h b/include/linux/kvm_types.h
> > index ac1ebb37a0ff..1dcfba68076a 100644
> > --- a/include/linux/kvm_types.h
> > +++ b/include/linux/kvm_types.h
> > @@ -87,6 +87,7 @@ struct gfn_to_pfn_cache {
> >  struct kvm_mmu_memory_cache {
> >         int nobjs;
> >         gfp_t gfp_zero;
> > +       gfp_t gfp_custom;
> >         struct kmem_cache *kmem_cache;
> >         void *objects[KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE];
> >  };
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index a49df8988cd6..e3a6f7647474 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -386,7 +386,9 @@ int kvm_mmu_topup_memory_cache(struct kvm_mmu_memory_cache *mc, int min)
> >         if (mc->nobjs >= min)
> >                 return 0;
> >         while (mc->nobjs < ARRAY_SIZE(mc->objects)) {
> > -               obj = mmu_memory_cache_alloc_obj(mc, GFP_KERNEL_ACCOUNT);
> > +               obj = mmu_memory_cache_alloc_obj(mc, (mc->gfp_custom) ?
> > +                                                mc->gfp_custom :
> > +                                                GFP_KERNEL_ACCOUNT);
> >                 if (!obj)
> >                         return mc->nobjs >= min ? 0 : -ENOMEM;
> >                 mc->objects[mc->nobjs++] = obj;
> > --
> > 2.34.1
> >
>
> Acked-by: Atish Patra <atishp@...osinc.com>

I have queued this patch for 5.20.

Please let me know if you are not okay or need changes in this patch.

Thanks,
Anup