Re: [Qemu-devel] [PATCH v2 1/1] parallels: add format spec

[Stefan Hajnoczi]

On Mon, Nov 23, 2015 at 04:32:37PM +0300, Denis V. Lunev wrote:
> From: Vladimir Sementsov-Ogievskiy <address@hidden>
> 
> This specifies Parallels image format as implemented in Parallels Cloud
> Server 6.10
> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> Signed-off-by: Denis V. Lunev <address@hidden>
> CC: Eric Blake <address@hidden>
> CC: John Snow <address@hidden>
> CC: Stefan Hajnoczi <address@hidden>
> ---
> v2: add license info
>     switch to offsets from types in field descriptions

Cool!  Thanks for publishing a specification.  This will help everyone
understand the code.

> +=== Dirty bitmaps feature ===
> +
> +This feature provides a way of storing dirty bitmaps in the image. The fields
> +of its data area are:
> +
> +   0 -  7:    size
> +              The bitmap size, should be equal to disk size in sectors.
> +
> +   8 - 23:    id
> +              An identifier for backup consistency checking.
> +
> +  24 - 27:    granularity
> +              Bitmap granularity, in sectors. I.e., the number of sectors
> +              corresponding to one bit of the bitmap.

Does this need to be a power of 2?

> +  28 - 31:    l1_size
> +              The number of entries in the L1 table of the bitmap.
> +
> +  variable:   l1 (64 * l1_size bytes)
> +              L1 offset table (in bytes)
> +
> +A dirty bitmap is stored using a one-level structure for the mapping to host
> +clusters - an L1 table.
> +
> +Given an offset into the bitmap, the offset in bytes into the image file can 
> be

What are the units of the offset into the bitmap?  Is it a bit number
(i.e. sector number / granularity)?

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