linux-kernel - Re: [PATCH v7 06/12] arm64/boot: Enable EL2 requirements for SPE_FEAT

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Message-ID: <20250901101904.GK745921@e132581.arm.com>
Date: Mon, 1 Sep 2025 11:19:04 +0100
From: Leo Yan <leo.yan@....com>
To: James Clark <james.clark@...aro.org>
Cc: Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
	Jonathan Corbet <corbet@....net>, Marc Zyngier <maz@...nel.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Anshuman Khandual <anshuman.khandual@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-perf-users@...r.kernel.org, linux-doc@...r.kernel.org,
	kvmarm@...ts.linux.dev
Subject: Re: [PATCH v7 06/12] arm64/boot: Enable EL2 requirements for
 SPE_FEAT_FDS

On Thu, Aug 14, 2025 at 10:25:28AM +0100, James Clark wrote:

[...]

> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
> index 3a4ca7f9acfb..a0361ddcdca4 100644
> --- a/arch/arm64/include/asm/el2_setup.h
> +++ b/arch/arm64/include/asm/el2_setup.h
> @@ -392,6 +392,17 @@
>  	orr	x0, x0, #HDFGRTR2_EL2_nPMICFILTR_EL0
>  	orr	x0, x0, #HDFGRTR2_EL2_nPMUACR_EL1
>  .Lskip_pmuv3p9_\@:
> +	/* If SPE is implemented, */
> +	__spe_vers_imp .Lskip_spefds_\@, ID_AA64DFR0_EL1_PMSVer_IMP, x1
> +	/* we can read PMSIDR and */
> +	mrs_s	x1, SYS_PMSIDR_EL1
> +	and	x1, x1,  #PMSIDR_EL1_FDS
> +	/* if FEAT_SPE_FDS is implemented, */
> +	cbz	x1, .Lskip_spefds_\@
> +	/* disable traps to PMSDSFR. */

Nitpick: the comment is a bit ambiguous for me. Would it be better to
say "disable traps to EL2" or "set the PMSDSFR bit to disable trapping" ?

Otherwise, LGTM:

Reviewed-by: Leo Yan <leo.yan@....com>

> +	orr	x0, x0, #HDFGRTR2_EL2_nPMSDSFR_EL1
> +
> +.Lskip_spefds_\@:
>  	msr_s   SYS_HDFGRTR2_EL2, x0
>  	msr_s   SYS_HDFGWTR2_EL2, x0
>  	msr_s   SYS_HFGRTR2_EL2, xzr
> 
> -- 
> 2.34.1
>