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Re: [Qemu-devel] [PATCH] block: Fix vpc initialization of the Dynamic Di
From: |
Andreas Färber |
Subject: |
Re: [Qemu-devel] [PATCH] block: Fix vpc initialization of the Dynamic Disk Header |
Date: |
Wed, 09 Nov 2011 17:38:51 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20110929 Thunderbird/7.0.1 |
Am 09.11.2011 17:32, schrieb Charles Arnold:
>>>> On 11/9/2011 at 08:58 AM, in message <address@hidden>, Kevin Wolf
> <address@hidden> wrote:
>>
>> Right, I'm not arguing that your change is wrong. What I'm asking for is
>> just something like:
>>
>> - dyndisk_header->data_offset = be64_to_cpu(0xFFFFFFFF);
>> + /* Note: The spec is actually wrong here, it says 0xFFFFFFFF, but
>> MS tools expect all 64 bits to be set */
>> + dyndisk_header->data_offset = be64_to_cpu(0xFFFFFFFFFFFFFFFFULL);
>>
>> Kevin
>
> Ok, I had the header comment on the brain, not a code comment.
> Here is the revised patch.
>
> - Charles
>
>
> The Data Offset field in the Dynamic Disk Header is an 8 byte field.
> Although the specification (2006-10-11) gives an example of initializing
> only the first 4 bytes, images generated by Microsoft on Windows initialize
> all 8 bytes.
>
> Failure to initialize all 8 bytes results in errors from utilities
> like Citrix's vhd-util which checks specifically for the proper Data
> Offset field initialization.
>
> Signed-off-by: Charles Arnold <address@hidden>
Reviewed-by: Andreas Färber <address@hidden>
Andreas
>
> diff --git a/block/vpc.c b/block/vpc.c
> index 416f489..179c6ae 100644
> --- a/block/vpc.c
> +++ b/block/vpc.c
> @@ -585,7 +585,11 @@ static int vpc_create(const char *filename,
> QEMUOptionParameter *options)
>
> memcpy(dyndisk_header->magic, "cxsparse", 8);
>
> - dyndisk_header->data_offset = be64_to_cpu(0xFFFFFFFF);
> + /*
> + * Note: The spec is actually wrong here for data_offset, it says
> + * 0xFFFFFFFF, but MS tools expect all 64 bits to be set.
> + */
> + dyndisk_header->data_offset = be64_to_cpu(0xFFFFFFFFFFFFFFFFULL);
> dyndisk_header->table_offset = be64_to_cpu(3 * 512);
> dyndisk_header->version = be32_to_cpu(0x00010000);
> dyndisk_header->block_size = be32_to_cpu(block_size);
--
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