Re: [Qemu-devel] [Bug 1749016] [NEW] VHDX BAT and Metadata Region Header Required Bit Not Set

[Stefan Hajnoczi]

On Mon, Feb 12, 2018 at 09:44:09PM -0000, Michael Fruchtman wrote:
> Public bug reported:
> 
> When converting a VMDK to VHDX the resulting VHDX's Region table has a
> small error. According to the VHDX specification the BAT and Metadata
> entries for the region header required bit should be set to 1.  In a
> VHDX created by qemu-img, this bit is not set.

CCing Jeff Cody, VHDX maintainer.

> 
> See Table 4: Known Region Properties of the VHDX specification.
> 
> The structure format is as following from Structure 4: Region Table
> Entry:
> 
> struct VHDX_REGION_TABLE_ENTRY {
> GUID Guid;
> UINT64 FileOffset;
> UINT32 Length;
> UINT32 Required:1;
> UINT32 Reserved:31;
> }
> 
> The Required bit for VHDX specified BAT and Metadata Regions Required
> bit in the entry is not set as required in the current specification.
> 
> VHDX Region Table in a valid VHDX
> 
> Offset(h)    00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
> 0x00030000   72 65 67 69 AE 8C 6B C6 02 00 00 00 00 00 00 00
> 0x00030010   66 77 C2 2D 23 F6 00 42 9D 64 11 5E 9B FD 4A 08
> 0x00030020   00 00 30 00 00 00 00 00 00 00 10 00 01 00 00 00  
> 0x00030030   06 A2 7C 8B 90 47 9A 4B B8 FE 57 5F 05 0F 88 6E
> 0x00030040   00 00 20 00 00 00 00 00 00 00 10 00 01 00 00 00
> 
> VHDX Region Table in a VHDX converted by qemu-img from VMDK
> 
> Offset(h)    00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
> 0x00030000   72 65 67 69 AE 8C 6B C6 02 00 00 00 00 00 00 00
> 0x00030010   66 77 C2 2D 23 F6 00 42 9D 64 11 5E 9B FD 4A 08
> 0x00030020   00 00 30 00 00 00 00 00 00 00 10 00 00 00 00 00  
> 0x00030030   06 A2 7C 8B 90 47 9A 4B B8 FE 57 5F 05 0F 88 6E
> 0x00030040   00 00 20 00 00 00 00 00 00 00 10 00 00 00 00 00
> 
> The fist bit at 0x0003002A and 0x0003004A should be set to 1.
> 
> ** Affects: qemu
>      Importance: Undecided
>          Status: New
> 
> 
> ** Tags: qemu-img vhdx
> 
> -- 
> You received this bug notification because you are a member of qemu-
> devel-ml, which is subscribed to QEMU.
> https://bugs.launchpad.net/bugs/1749016
> 
> Title:
>   VHDX BAT and Metadata Region Header Required Bit Not Set
> 
> Status in QEMU:
>   New
> 
> Bug description:
>   When converting a VMDK to VHDX the resulting VHDX's Region table has a
>   small error. According to the VHDX specification the BAT and Metadata
>   entries for the region header required bit should be set to 1.  In a
>   VHDX created by qemu-img, this bit is not set.
> 
>   See Table 4: Known Region Properties of the VHDX specification.
> 
>   The structure format is as following from Structure 4: Region Table
>   Entry:
> 
>   struct VHDX_REGION_TABLE_ENTRY {
>   GUID Guid;
>   UINT64 FileOffset;
>   UINT32 Length;
>   UINT32 Required:1;
>   UINT32 Reserved:31;
>   }
> 
>   The Required bit for VHDX specified BAT and Metadata Regions Required
>   bit in the entry is not set as required in the current specification.
> 
>   VHDX Region Table in a valid VHDX
> 
>   Offset(h)    00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
>   0x00030000   72 65 67 69 AE 8C 6B C6 02 00 00 00 00 00 00 00
>   0x00030010   66 77 C2 2D 23 F6 00 42 9D 64 11 5E 9B FD 4A 08
>   0x00030020   00 00 30 00 00 00 00 00 00 00 10 00 01 00 00 00  
>   0x00030030   06 A2 7C 8B 90 47 9A 4B B8 FE 57 5F 05 0F 88 6E
>   0x00030040   00 00 20 00 00 00 00 00 00 00 10 00 01 00 00 00
> 
>   VHDX Region Table in a VHDX converted by qemu-img from VMDK
> 
>   Offset(h)    00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
>   0x00030000   72 65 67 69 AE 8C 6B C6 02 00 00 00 00 00 00 00
>   0x00030010   66 77 C2 2D 23 F6 00 42 9D 64 11 5E 9B FD 4A 08
>   0x00030020   00 00 30 00 00 00 00 00 00 00 10 00 00 00 00 00  
>   0x00030030   06 A2 7C 8B 90 47 9A 4B B8 FE 57 5F 05 0F 88 6E
>   0x00030040   00 00 20 00 00 00 00 00 00 00 10 00 00 00 00 00
> 
>   The fist bit at 0x0003002A and 0x0003004A should be set to 1.
> 
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>

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