linux-kernel - Re: [PATCH 1/1] arm64: enable PREEMPT

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250305110651.6dpe0xQU@linutronix.de>
Date: Wed, 5 Mar 2025 12:06:51 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Valentin Schneider <vschneid@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
	Mike Galbraith <efault@....de>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Peter Collingbourne <pcc@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
	Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
	Mark Brown <broonie@...nel.org>,
	Kristina Martsenko <kristina.martsenko@....com>,
	Petr Tesarik <ptesarik@...e.com>,
	Jinjie Ruan <ruanjinjie@...wei.com>,
	Juri Lelli <juri.lelli@...hat.com>, Phil Auld <pauld@...hat.com>,
	Clark Williams <williams@...hat.com>
Subject: Re: [PATCH 1/1] arm64: enable PREEMPT_LAZY

On 2025-03-05 11:49:25 [+0100], Valentin Schneider wrote:
> From: Mark Rutland <mark.rutland@....com>
> 
> For an architecture to enable CONFIG_ARCH_HAS_RESCHED_LAZY, two things are
> required:
> 1) Adding a TIF_NEED_RESCHED_LAZY flag definition
> 2) Checking for TIF_NEED_RESCHED_LAZY in the appropriate locations
> 
> 2) is handled in a generic manner by CONFIG_GENERIC_ENTRY, which isn't
> (yet) implemented for arm64. However, outside of core scheduler code,
> TIF_NEED_RESCHED_LAZY only needs to be checked on a kernel exit, meaning:
> o return/entry to userspace.
> o return/entry to guest.
> 
> The return/entry to a guest is all handled by xfer_to_guest_mode_handle_work()
> which already does the right thing, so it can be left as-is.
> 
> arm64 doesn't use common entry's exit_to_user_mode_prepare(), so update its
> return to user path to check for TIF_NEED_RESCHED_LAZY and call into
> schedule() accordingly.
> 
> Link: https://lore.kernel.org/linux-rt-users/20241216190451.1c61977c@mordecai.tesarici.cz/
> Link: https://lore.kernel.org/all/xhsmh4j0fl0p3.mognet@vschneid-thinkpadt14sgen2i.remote.csb/
> Signed-off-by: Mark Rutland <mark.rutland@....com>
> [testdrive, _TIF_WORK_MASK fixlet and changelog.]
> Signed-off-by: Mike Galbraith <efault@....de>
> [Another round of testing; changelog faff]
> Signed-off-by: Valentin Schneider <vschneid@...hat.com>

I somehow assumed it was already merged. For what it is worth, this
looks like patch Mike posted in
	https://lore.kernel.org/a198a7dd9076f97b89d8882bb249b3bf303564ef.camel@gmx.de

and tested 

Reviewed-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

Sebastian