linux-kernel - Re: [PATCH] Revert "KVM: Eliminate extra function calls in kvm_get_dirty_log

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Message-ID: <c253c775-bc32-7cb4-e090-3f5764ea1285@redhat.com>
Date:   Thu, 14 Feb 2019 17:42:05 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     lantianyu1986@...il.com
Cc:     Lan Tianyu <Tianyu.Lan@...rosoft.com>, rkrcmar@...hat.com,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        sean.j.christopherson@...el.com
Subject: Re: [PATCH] Revert "KVM: Eliminate extra function calls in
 kvm_get_dirty_log_protect()"

On 02/02/19 10:20, lantianyu1986@...il.com wrote:
> From: Lan Tianyu <Tianyu.Lan@...rosoft.com>
> 
> The value of "dirty_bitmap[i]" is already check before setting its value
> to mask. The following check of "mask" is redundant. The check of "mask" was
> introduced by commit 58d2930f4ee3(("KVM: Eliminate extra function calls in
> kvm_get_dirty_log_protect()"). This patch is to revert the patch.
> 
> Signed-off-by: Lan Tianyu <Tianyu.Lan@...rosoft.com>
> ---
>  virt/kvm/kvm_main.c | 8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 2bdc827b9ee9..ef06cfb9b52b 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1200,11 +1200,9 @@ int kvm_get_dirty_log_protect(struct kvm *kvm,
>  			mask = xchg(&dirty_bitmap[i], 0);
>  			dirty_bitmap_buffer[i] = mask;
>  
> -			if (mask) {
> -				offset = i * BITS_PER_LONG;
> -				kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
> -									offset, mask);
> -			}
> +			offset = i * BITS_PER_LONG;
> +			kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot,
> +								offset, mask);
>  		}
>  		spin_unlock(&kvm->mmu_lock);
>  	}
> 

Queued, thanks.

Paolo