Re: [Qemu-devel] [PATCH] block: Fix vpc initialization of the Dynamic Disk Header

[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>

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);