linux-kernel - Re: [PATCH v11 RESEND 9/9] arm64: armv8_deprecated: apply FEAT

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] [day] [month] [year] [list]

Message-ID: <aT/bNLQyKcrAZ6Fb@e129823.arm.com>
Date: Mon, 15 Dec 2025 09:56:04 +0000
From: Yeoreum Yun <yeoreum.yun@....com>
To: Marc Zyngier <maz@...nel.org>
Cc: catalin.marinas@....com, will@...nel.org, broonie@...nel.org,
	oliver.upton@...ux.dev, miko.lenczewski@....com,
	kevin.brodsky@....com, ardb@...nel.org, suzuki.poulose@....com,
	lpieralisi@...nel.org, yangyicong@...ilicon.com,
	scott@...amperecomputing.com, joey.gouly@....com,
	yuzenghui@...wei.com, pbonzini@...hat.com, shuah@...nel.org,
	mark.rutland@....com, arnd@...db.de,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev, kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v11 RESEND 9/9] arm64: armv8_deprecated: apply FEAT_LSUI
 for swpX emulation.

Hi,

> On Sun, 14 Dec 2025 11:22:48 +0000,
> Yeoreum Yun <yeoreum.yun@....com> wrote:
> >
> > Apply the FEAT_LSUI instruction to emulate the deprecated swpX
> > instruction, so that toggling of the PSTATE.PAN bit can be removed when
> > LSUI-related instructions are used.
> >
> > Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
>
> It really begs the question: what are the odds of ever seeing a CPU
> that implements both LSUI and AArch32?
>
> This seems extremely unlikely to me.

Well, I'm not sure how many CPU will have
both ID_AA64PFR0_EL1.EL0 bit as 0b0010 and FEAT_LSUI
(except FVP currently) -- at least the CPU what I saw,
most of them set ID_AA64PFR0_EL1.EL0 as 0b0010.

If you this seems useless, I don't have any strong comments
whether drop patches related to deprecated swp instruction parts
(patch 8-9 only) or not.
(But, I hope to pass this decision to maintaining perspective...)

>
> 	M.
>
> --
> Without deviation from the norm, progress is not possible.

--
Sincerely,
Yeoreum Yun