Re: [Qemu-devel] [PATCH v2 4/9] block: vhdx - log support struct and defines

[Stefan Hajnoczi <stefanha@redhat.com>]

On Wed, Jul 31, 2013 at 11:23:49PM -0400, Jeff Cody wrote:
> @@ -318,6 +323,18 @@ typedef struct VHDXMetadataEntries {
>      uint16_t present;
>  } VHDXMetadataEntries;
>  
> +typedef struct VHDXLogEntries {
> +    uint64_t offset;
> +    uint64_t length;
> +    uint32_t head;
> +    uint32_t tail;
> +} VHDXLogEntries;
> +
> +typedef struct VHDXLogEntryInfo {
> +    uint64_t sector_start;
> +    uint32_t desc_count;
> +} VHDXLogEntryInfo;

An array of VHDXLogEntryInfo structs would be affected by alignment on
x86_64.  &a[1] != (void*)a + sizeof(VHDXLogEntryInfo).

IMO all on-disk structs should be QEMU_PACKED for safety.