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Re: [Qemu-devel] [PATCH 1/3] qcow2: Set MIN_L2_CACHE_SIZE to 2
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From: |
Alexander Graf |
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Subject: |
Re: [Qemu-devel] [PATCH 1/3] qcow2: Set MIN_L2_CACHE_SIZE to 2 |
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Date: |
Mon, 01 Jun 2015 18:12:48 +0200 |
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User-agent: |
Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
On 01.06.15 18:09, Max Reitz wrote:
> The L2 cache must cover at least two L2 tables, because during COW two
> L2 tables are accessed simultaneously.
>
> Reported-by: Alexander Graf <address@hidden>
> Cc: qemu-stable <address@hidden>
> Signed-off-by: Max Reitz <address@hidden>
Tested-by: Alexander Graf <address@hidden>
Alex
> ---
> block/qcow2.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/qcow2.h b/block/qcow2.h
> index 0076512..aa20022 100644
> --- a/block/qcow2.h
> +++ b/block/qcow2.h
> @@ -62,7 +62,8 @@
> #define MIN_CLUSTER_BITS 9
> #define MAX_CLUSTER_BITS 21
>
> -#define MIN_L2_CACHE_SIZE 1 /* cluster */
> +/* Must be at least 2 to cover COW */
> +#define MIN_L2_CACHE_SIZE 2 /* clusters */
>
> /* Must be at least 4 to cover all cases of refcount table growth */
> #define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */
>