linux-kernel - Re: [PATCH 04/10] arm64/boot: Enable EL2 requirements for SPE_FEAT

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Message-ID: <20250520110450.GN412060@e132581.arm.com>
Date: Tue, 20 May 2025 12:04:50 +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>,
	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>,
	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>,
	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 04/10] arm64/boot: Enable EL2 requirements for
 SPE_FEAT_FDS

On Tue, May 06, 2025 at 12:41:36PM +0100, James Clark wrote:
> SPE data source filtering (optional from Armv8.8) requires that traps to
> the filter register PMSDSFR be disabled. Document the requirements and
> disable the traps if the feature is present.
> 
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
>  Documentation/arch/arm64/booting.rst | 11 +++++++++++
>  arch/arm64/include/asm/el2_setup.h   | 14 ++++++++++++++
>  2 files changed, 25 insertions(+)
> 
> diff --git a/Documentation/arch/arm64/booting.rst b/Documentation/arch/arm64/booting.rst
> index dee7b6de864f..8da6801da9a0 100644
> --- a/Documentation/arch/arm64/booting.rst
> +++ b/Documentation/arch/arm64/booting.rst
> @@ -404,6 +404,17 @@ Before jumping into the kernel, the following conditions must be met:
>      - HDFGWTR2_EL2.nPMICFILTR_EL0 (bit 3) must be initialised to 0b1.
>      - HDFGWTR2_EL2.nPMUACR_EL1 (bit 4) must be initialised to 0b1.
>  
> +  For CPUs with SPE data source filtering (SPE_FEAT_FDS):

For alignment with Arm ARM:

s/SPE_FEAT_FDS/FEAT_SPE_FDS

> +
> +  - If EL3 is present:
> +
> +    - MDCR_EL3.EnPMS3 (bit 42) must be initialised to 0b1.
> +
> +  - If the kernel is entered at EL1 and EL2 is present:
> +
> +    - HDFGRTR2_EL2.nPMSDSFR_EL1 (bit 19) must be initialised to 0b1.
> +    - HDFGWTR2_EL2.nPMSDSFR_EL1 (bit 19) must be initialised to 0b1.
> +
>    For CPUs with Memory Copy and Memory Set instructions (FEAT_MOPS):
>  
>    - If the kernel is entered at EL1 and EL2 is present:
> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
> index ebceaae3c749..155b45092f5e 100644
> --- a/arch/arm64/include/asm/el2_setup.h
> +++ b/arch/arm64/include/asm/el2_setup.h
> @@ -275,6 +275,20 @@
>  	orr	x0, x0, #HDFGRTR2_EL2_nPMICFILTR_EL0
>  	orr	x0, x0, #HDFGRTR2_EL2_nPMUACR_EL1
>  .Lskip_pmuv3p9_\@:
> +	mrs	x1, id_aa64dfr0_el1
> +	ubfx	x1, x1, #ID_AA64DFR0_EL1_PMSVer_SHIFT, #4
> +	/* If SPE is implemented, we can read PMSIDR and */
> +	cmp	x1, #ID_AA64DFR0_EL1_PMSVer_IMP
> +	b.lt	.Lskip_spefds_\@
> +
> +	mrs_s	x1, SYS_PMSIDR_EL1
> +	and	x1, x1, PMSIDR_EL1_FDS_SHIFT

Should be:

        and     x1, x1, #(1 << PMSIDR_EL1_FDS_SHIFT)

> +	/* if FEAT_SPE_FDS is implemented, */
> +	cbz	x1, .Lskip_spefds_\@
> +	/* disable traps to PMSDSFR. */
> +	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
>