From: "Philippe Mathieu-Daudé" <philmd@linaro.org>
To: Thomas Huth <thuth@redhat.com>,
Pierrick Bouvier <pierrick.bouvier@linaro.org>,
qemu-devel@nongnu.org
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Mahmoud Mandour" <ma.mandourr@gmail.com>,
"Alexandre Iooss" <erdnaxe@crans.org>,
"Markus Armbruster" <armbru@redhat.com>,
"Marc-André Lureau" <marcandre.lureau@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>,
"Stefano Garzarella" <sgarzare@redhat.com>
Subject: Re: [PATCH v3 2/3] docs/devel/style: add a section about bitfield, and disallow them for packed structures
Date: Tue, 10 Dec 2024 11:10:58 +0100 [thread overview]
Message-ID: <1424773d-1e06-4581-bd5b-6b216e4bad5b@linaro.org> (raw)
In-Reply-To: <a88854b4-5004-4734-9fc4-6f34eafba5a9@redhat.com>
On 10/12/24 08:52, Thomas Huth wrote:
> On 09/12/2024 21.33, Philippe Mathieu-Daudé wrote:
>> On 28/11/24 21:15, Pierrick Bouvier wrote:
>>> Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
> ...
>>> +For this reason, we disallow usage of bitfields in packed structures
>>> and in any
>>> +structures which are supposed to exactly match a specific layout in
>>> guest
>>> +memory. Some existing code may use it, and we carefully ensured the
>>> layout was
>>> +the one expected.
>>> +
>>> +We also suggest avoiding bitfields even in structures where the exact
>>> +layout does not matter, unless you can show that they provide a
>>> significant
>>> +memory usage or usability benefit.
>>
>> I don't think we should mention "significant memory usage benefit".
>
> Why not? That's the point of bitfields, isn't it? Or do you mean it's
> included in "usability benefit" already?
To not generate a reactance effect :) Developers trying to optimize
memory usage via bit field uses is extremely rare (at least in the
QEMU community).
Anyhow, I don't object to this patch as is.
next prev parent reply other threads:[~2024-12-10 10:11 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-28 20:15 [PATCH v3 0/3] Enable clang build on Windows Pierrick Bouvier
2024-11-28 20:15 ` [PATCH v3 1/3] win32: remove usage of attribute gcc_struct Pierrick Bouvier
2024-11-28 21:01 ` Richard Henderson
2024-11-28 20:15 ` [PATCH v3 2/3] docs/devel/style: add a section about bitfield, and disallow them for packed structures Pierrick Bouvier
2024-11-28 21:02 ` Richard Henderson
2024-12-09 20:33 ` Philippe Mathieu-Daudé
2024-12-09 22:15 ` Pierrick Bouvier
2024-12-10 7:52 ` Thomas Huth
2024-12-10 10:10 ` Philippe Mathieu-Daudé [this message]
2024-12-10 18:45 ` Pierrick Bouvier
2024-11-28 20:15 ` [PATCH v3 3/3] plugins: enable linking with clang/lld Pierrick Bouvier
2025-01-10 8:03 ` Philippe Mathieu-Daudé
2024-12-09 18:34 ` [PATCH v3 0/3] Enable clang build on Windows Pierrick Bouvier
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