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

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Message-ID: <CAOnJCUKNaNz0iF5dfS9quRyDS_ZD1adWWAFjOnBPwqKEefpS8Q@mail.gmail.com>
Date:   Tue, 12 Jul 2022 18:27:08 -0700
From:   Atish Patra <atishp@...shpatra.org>
To:     Anup Patel <apatel@...tanamicro.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Alistair Francis <Alistair.Francis@....com>,
        Anup Patel <anup@...infault.org>,
        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>
Subject: Re: [PATCH 1/5] KVM: Add gfp_custom flag in struct kvm_mmu_memory_cache

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>

-- 
Regards,
Atish