linux-kernel - Re: [PATCH] RISC-V: KVM: Simplify kvm_arch_prepare_memory

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Date:   Sun, 27 Nov 2022 18:07:17 +0530
From:   Anup Patel <anup@...infault.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     Atish Patra <atishp@...shpatra.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH] RISC-V: KVM: Simplify kvm_arch_prepare_memory_region()

On Sun, Nov 13, 2022 at 7:22 PM Christophe JAILLET
<christophe.jaillet@...adoo.fr> wrote:
>
> In kvm_arch_prepare_memory_region(), if no error occurs, a spin_lock()/
> spin_unlock() call can be avoided.
>
> Switch to kvm_riscv_gstage_iounmap() that is the same as the current code,
> but with a better semantic.
> It also embeds the locking logic. So it is avoided if ret == 0.
>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>

Looks good to me.

Reviewed-by: Anup Patel <anup@...infault.org>

I have tested this on QEMU virt machine for RV64.

Queued this patch for Linux-6.2

Thanks,
Anup

> ---
> I don't use cross-compiler, so this patch is NOT even compile tested.
> ---
>  arch/riscv/kvm/mmu.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
> index 3620ecac2fa1..c8834e463763 100644
> --- a/arch/riscv/kvm/mmu.c
> +++ b/arch/riscv/kvm/mmu.c
> @@ -537,10 +537,8 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
>         if (change == KVM_MR_FLAGS_ONLY)
>                 goto out;
>
> -       spin_lock(&kvm->mmu_lock);
>         if (ret)
> -               gstage_unmap_range(kvm, base_gpa, size, false);
> -       spin_unlock(&kvm->mmu_lock);
> +               kvm_riscv_gstage_iounmap(kvm, base_gpa, size);
>
>  out:
>         mmap_read_unlock(current->mm);
> --
> 2.34.1
>