From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([140.186.70.92]:50643)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <weil@mail.berlios.de>) id 1Qxtyz-0000yh-Jo
	for qemu-devel@nongnu.org; Mon, 29 Aug 2011 01:02:02 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <weil@mail.berlios.de>) id 1Qxtyy-00074c-Jb
	for qemu-devel@nongnu.org; Mon, 29 Aug 2011 01:02:01 -0400
Received: from v220110690675601.yourvserver.net ([78.47.199.172]:58708)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <weil@mail.berlios.de>) id 1Qxtyy-00074K-DC
	for qemu-devel@nongnu.org; Mon, 29 Aug 2011 01:02:00 -0400
Message-ID: <4E5B1D42.1010605@mail.berlios.de>
Date: Mon, 29 Aug 2011 07:01:54 +0200
From: Stefan Weil <weil@mail.berlios.de>
MIME-Version: 1.0
References: <1314564200-6872-1-git-send-email-weil@mail.berlios.de>
	<CAAu8pHuUbXiw4rXwWE_bG2dvy=at7-MBnkWOiFhCPz9UuAx1MQ@mail.gmail.com>
In-Reply-To: <CAAu8pHuUbXiw4rXwWE_bG2dvy=at7-MBnkWOiFhCPz9UuAx1MQ@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH 0/7] Fix packing for MinGW with
	-mms-bitfields
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Blue Swirl <blauwirbel@gmail.com>
Cc: Kevin Wolf <kwolf@redhat.com>, QEMU Developers <qemu-devel@nongnu.org>, Alexander Graf <agraf@suse.de>, Isaku Yamahata <yamahata@valinux.co.jp>, Jan Kiszka <jan.kiszka@web.de>, Gerd Hoffmann <kraxel@redhat.com>

Am 28.08.2011 23:43, schrieb Blue Swirl:
> On Sun, Aug 28, 2011 at 8:43 PM, Stefan Weil <weil@mail.berlios.de> wrote:
>> These patches fix the packing of structures which were affected by
>> the new compiler attribute -mms-bitfields (which is needed for glib-2.0).
>>
>> I compiled qemu.exe with and without -mms-bitfields and compared
>> the resulting struct alignment using pahole and codiff.
>
> If a structure is only used internally by QEMU (not used in network,
> disk or guest interfaces), changes in padding don't matter. In fact,
> in those cases it may be better to remove the packing, because then
> the fields may be naturally aligned and that gives better performance
> on most architectures. Could you please check if this is the case for
> any of the structs?

I did this already, but also forward your question to the maintainers.
Here is my result:

[PATCH 2/7] block/vvfat: Fix packing for w32: needs packing (disk)
[PATCH 3/7] acpi: Fix packing for w32: needs packing (bios interface)
[PATCH 4/7] hpet: Fix packing for w32: needs packing (bios interface)
[PATCH 5/7] usb: Fix packing for w32: needs packing (usb interface)
[PATCH 6/7] virtio: Fix packing for w32: needs packing? (guest interface?)
[PATCH 7/7] slirp: Fix packing for w32: needs packing (network interface)

All those struct statements need the pack attribute (otherwise the code
would have to be rewritten which is of course always possible).