Re: [Qemu-devel] [PATCH for-2.11] iotests: Fix 176 on 32-bit host

[Max Reitz <mreitz@redhat.com>]

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On 2017-11-17 20:04, Eric Blake wrote:
> The contents of a qcow2 bitmap are rounded up to a size that
> matches the number of bits available for the granularity, but
> that granularity differs for 32-bit hosts (our default 64k
> cluster allows for 2M bitmap coverage per 'long') and 64-bit
> hosts (4M bitmap per 'long').  If the image is a multiple of
> 2M but not 4M, then the number of bytes occupied by the array
> of longs in memory differs between architecture, thus
> resulting in different SHA256 hashes.
> 
> Furthermore (but untested by me), if our computation of the
> SHA256 hash is at all endian-dependent because of how we store
> data in memory, that's another variable we'd have to account
> for (ideally, we specified the bitmap stored in qcow2 as
> fixed-endian on disk, because the same qcow2 file must be
> usable across any architecture; but that says nothing about
> how we represent things in memory).  But we already have test
> 165 to validate that bitmaps are stored correctly on disk,
> while this test is merely testing that the bitmap exists.
> 
> So for this test, the easiest solution is to filter out the
> actual hash value.  Broken in commit 4096974e.
> 
> Reported-by: Max Reitz <mreitz@redhat.com>
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  tests/qemu-iotests/176     | 3 ++-
>  tests/qemu-iotests/176.out | 8 ++++----
>  2 files changed, 6 insertions(+), 5 deletions(-)

Now that I've failed to keep my tree empty anyway:

Thanks, applied to my block branch:

https://github.com/XanClic/qemu/commits/block

(No offense taken if **someone** *cough* *cough* were to take it from me)

Max


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