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

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Message-ID: <bd224e52-d786-4922-b2ba-b52f0c73badf@linaro.org>
Date: Mon, 1 Sep 2025 13:21:01 +0100
From: James Clark <james.clark@...aro.org>
To: Leo Yan <leo.yan@....com>
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 01/09/2025 11:19 am, Leo Yan wrote:
> 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>

The bit we're setting is actually called nPMSDSFR_EL1, but I can change 
it to:

   /* disable traps of PMSDSFR to EL2 */

> 
>> +	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
>>