linux-kernel - Re: [PATCH v8 08/14] KVM: selftests: Always clear dirty bitmap after iteration

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Date:   Wed, 1 Apr 2020 09:04:01 +0200
From:   Andrew Jones <drjones@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Kevin Tian <kevin.tian@...el.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Christophe de Dinechin <dinechin@...hat.com>,
        Yan Zhao <yan.y.zhao@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>
Subject: Re: [PATCH v8 08/14] KVM: selftests: Always clear dirty bitmap after
 iteration

On Tue, Mar 31, 2020 at 02:59:54PM -0400, Peter Xu wrote:
> We don't clear the dirty bitmap before because KVM_GET_DIRTY_LOG will
> clear it for us before copying the dirty log onto it.  However we'd
> still better to clear it explicitly instead of assuming the kernel
> will always do it for us.
> 
> More importantly, in the upcoming dirty ring tests we'll start to
> fetch dirty pages from a ring buffer, so no one is going to clear the
> dirty bitmap for us.
> 
> Signed-off-by: Peter Xu <peterx@...hat.com>
> ---
>  tools/testing/selftests/kvm/dirty_log_test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
> index 752ec158ac59..6a8275a22861 100644
> --- a/tools/testing/selftests/kvm/dirty_log_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_test.c
> @@ -195,7 +195,7 @@ static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long *bmap)
>  				    page);
>  		}
>  
> -		if (test_bit_le(page, bmap)) {
> +		if (test_and_clear_bit_le(page, bmap)) {
>  			host_dirty_count++;
>  			/*
>  			 * If the bit is set, the value written onto
> -- 
> 2.24.1
>

Reviewed-by: Andrew Jones <drjones@...hat.com>