[Qemu-devel] Fixing dma-helper qiov truncation

[Mark Cave-Ayland]

Now that the 2.8 tree is open, I'd like to resurrect this earlier patch
to switch the macio controller over to the new byte-aligned DMA helpers:
https://lists.gnu.org/archive/html/qemu-devel/2016-05/msg04907.html.

The first patch in the series is a hack to work around the issue that
byte-aligned qiovs are being truncated with the existing code. git blame
shows that this code was introduced by this commit:


commit 58f423fbd5f7f435e8dc56dfa565b043d20d1e1b
Author: Kevin Wolf <address@hidden>
Date:   Wed Jul 9 19:17:30 2014 +0200

    dma-helpers: Fix too long qiov

    If the size of the scatter/gather list isn't a multiple of 512, the
    number of sectors for the block layer request is rounded down, resulting
    in a qiov that doesn't match the request length. Truncate the qiov
to the
    new length of the request.

    This fixes the IDE qtest case /x86_64/ide/bmdma/short_prdt.

    Signed-off-by: Kevin Wolf <address@hidden>
    Reviewed-by: Eric Blake <address@hidden>


Kevin/Paolo - what should be the correct behaviour here given that the
underlying APIs are now byte-aligned?


ATB,

Mark.