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Re: [Qemu-devel] [PATCH for-2.11] iotests: Fix 176 on 32-bit host
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH for-2.11] iotests: Fix 176 on 32-bit host |
Date: |
Fri, 17 Nov 2017 13:10:10 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 |
On 11/17/2017 01:04 PM, 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.
Of course, if Kevin sends a v2 pull, it's probably better to just squash
this in to my original testsuite change (since a v2 would probably
invalidate that commit id).
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
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