linux-kernel - Re: [PATCH v5 0/6] initialize SCTRL2

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Message-ID: <aMrTkLhLOhas8Viy@willie-the-truck>
Date: Wed, 17 Sep 2025 16:28:16 +0100
From: Will Deacon <will@...nel.org>
To: Yeoreum Yun <yeoreum.yun@....com>
Cc: catalin.marinas@....com, broonie@...nel.org, oliver.upton@...ux.dev,
	anshuman.khandual@....com, robh@...nel.org, james.morse@....com,
	mark.rutland@....com, joey.gouly@....com, Dave.Martin@....com,
	ahmed.genidi@....com, kevin.brodsky@....com,
	scott@...amperecomputing.com, mbenes@...e.cz,
	james.clark@...aro.org, frederic@...nel.org, rafael@...nel.org,
	pavel@...nel.org, ryan.roberts@....com, suzuki.poulose@....com,
	maz@...nel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	kvmarm@...ts.linux.dev
Subject: Re: [PATCH v5 0/6] initialize SCTRL2_ELx

On Wed, Sep 17, 2025 at 03:56:12PM +0100, Yeoreum Yun wrote:
> This series introduces initial support for the SCTLR2_ELx registers in Linux.
> The feature is optional starting from ARMv8.8/ARMv9.3,
> and becomes mandatory from ARMv8.9/ARMv9.4.
> 
> Currently, Linux has no strict need to modify SCTLR2_ELx--
> at least assuming that firmware initializes
> these registers to reasonable defaults.
> 
> However, several upcoming architectural features will require configuring
> control bits in these registers.
> Notable examples include FEAT_PAuth_LR and FEAT_CPA2.
> 
> Patch History
> ==============
> from v4 to v5:
>   - using .ifc in set_sctlr2_elx
>   - change (re)initialise position after SCTLR_ELx
>   - add docs for SCTRL2_ELx
>   - rebase to v6.17-rc6
>   - https://lore.kernel.org/all/20250821172408.2101870-1-yeoreum.yun@arm.com/

Sorry, this is a really pedantic nit, but please can you fix the typo in
the subject if/when you next post this?

More importantly, as Dave says, I don't see the point in merging this
until we have a use for the register. At that point, your patches can
hopefully be a prefix of the series that uses it.

Will