From: Yeoreum Yun <yeoreum.yun@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: catalin.marinas@arm.com, will@kernel.org, broonie@kernel.org,
oliver.upton@linux.dev, miko.lenczewski@arm.com,
kevin.brodsky@arm.com, ardb@kernel.org, suzuki.poulose@arm.com,
lpieralisi@kernel.org, yangyicong@hisilicon.com,
scott@os.amperecomputing.com, joey.gouly@arm.com,
yuzenghui@huawei.com, pbonzini@redhat.com, shuah@kernel.org,
mark.rutland@arm.com, arnd@arndb.de,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev,
kvm@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v11 RESEND 9/9] arm64: armv8_deprecated: apply FEAT_LSUI for swpX emulation.
Date: Mon, 15 Dec 2025 09:56:04 +0000 [thread overview]
Message-ID: <aT/bNLQyKcrAZ6Fb@e129823.arm.com> (raw)
In-Reply-To: <86ms3knl6s.wl-maz@kernel.org>
Hi,
> On Sun, 14 Dec 2025 11:22:48 +0000,
> Yeoreum Yun <yeoreum.yun@arm.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@arm.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
next prev parent reply other threads:[~2025-12-15 9:57 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-14 11:22 [PATCH v11 RESEND 0/9] support FEAT_LSUI Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 1/9] arm64: cpufeature: add FEAT_LSUI Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 2/9] KVM: arm64: expose FEAT_LSUI to guest Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 3/9] KVM: arm64: kselftest: set_id_regs: add test for FEAT_LSUI Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 4/9] arm64: Kconfig: Detect toolchain support for LSUI Yeoreum Yun
2026-01-19 15:50 ` Will Deacon
2026-01-19 15:54 ` Mark Brown
2026-01-20 11:35 ` Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 5/9] arm64: futex: refactor futex atomic operation Yeoreum Yun
2026-01-19 15:57 ` Will Deacon
2026-01-19 22:19 ` Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 6/9] arm64: futex: support futex with FEAT_LSUI Yeoreum Yun
2026-01-19 16:37 ` Will Deacon
2026-01-19 22:17 ` Yeoreum Yun
2026-01-20 15:44 ` Yeoreum Yun
2026-01-21 13:48 ` Will Deacon
2026-01-21 14:16 ` Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 7/9] arm64: separate common LSUI definitions into lsui.h Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 8/9] arm64: armv8_deprecated: convert user_swpX to inline function Yeoreum Yun
2025-12-14 11:22 ` [PATCH v11 RESEND 9/9] arm64: armv8_deprecated: apply FEAT_LSUI for swpX emulation Yeoreum Yun
2025-12-15 9:33 ` Marc Zyngier
2025-12-15 9:56 ` Yeoreum Yun [this message]
2026-01-19 15:34 ` Will Deacon
2026-01-19 22:32 ` Yeoreum Yun
2026-01-20 9:32 ` Yeoreum Yun
2026-01-20 9:46 ` Mark Rutland
2026-01-20 10:07 ` Yeoreum Yun
2026-01-20 11:50 ` Will Deacon
2026-01-20 12:14 ` Yeoreum Yun
2026-01-20 17:59 ` Yeoreum Yun
2026-01-21 13:56 ` Will Deacon
2026-01-21 14:51 ` Yeoreum Yun
2026-01-21 16:20 ` Will Deacon
2026-01-21 16:31 ` Yeoreum Yun
2026-01-21 16:36 ` Will Deacon
2026-01-21 16:51 ` Yeoreum Yun
2025-12-31 10:07 ` [PATCH v11 RESEND 0/9] support FEAT_LSUI Yeoreum Yun
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