linux-kernel - Re: [PATCH v3 05/10] KVM: arm64: Add trap configs for PMSDSFR

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Message-ID: <20250709095357.GA2715835@e124191.cambridge.arm.com>
Date: Wed, 9 Jul 2025 10:53:57 +0100
From: Joey Gouly <joey.gouly@....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>,
	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>, leo.yan@....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 v3 05/10] KVM: arm64: Add trap configs for PMSDSFR_EL1

Hi James!

On Thu, Jun 05, 2025 at 11:49:03AM +0100, James Clark wrote:
> SPE data source filtering (SPE_FEAT_FDS) adds a new register
> PMSDSFR_EL1, add the trap configs for it. PMSNEVFR_EL1 was also missing
> its VNCR offset so add it along with PMSDSFR_EL1.
> 

A (well behaving) guest won't try access this because:
The presence of PMSDSFR_EL1 is checked by accessing PMSDSFR_EL1.FDS, which is
currently `undef_access` and we hide SPE from the guest in
read_sanitised_id_aa64dfr0_el1().

So makes sense it is just undef!

Reviewed-by: Joey Gouly <joey.gouly@....com>

Thanks,
Joey

> Tested-by: Leo Yan <leo.yan@....com>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
>  arch/arm64/include/asm/vncr_mapping.h | 2 ++
>  arch/arm64/kvm/emulate-nested.c       | 1 +
>  arch/arm64/kvm/sys_regs.c             | 1 +
>  3 files changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/vncr_mapping.h b/arch/arm64/include/asm/vncr_mapping.h
> index 6f556e993644..dba0e58a5fac 100644
> --- a/arch/arm64/include/asm/vncr_mapping.h
> +++ b/arch/arm64/include/asm/vncr_mapping.h
> @@ -92,6 +92,8 @@
>  #define VNCR_PMSICR_EL1         0x838
>  #define VNCR_PMSIRR_EL1         0x840
>  #define VNCR_PMSLATFR_EL1       0x848
> +#define VNCR_PMSNEVFR_EL1       0x850
> +#define VNCR_PMSDSFR_EL1        0x858
>  #define VNCR_TRFCR_EL1          0x880
>  #define VNCR_MPAM1_EL1          0x900
>  #define VNCR_MPAMHCR_EL2        0x930
> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
> index 3a384e9660b8..60bd8b7f0e5b 100644
> --- a/arch/arm64/kvm/emulate-nested.c
> +++ b/arch/arm64/kvm/emulate-nested.c
> @@ -1174,6 +1174,7 @@ static const struct encoding_to_trap_config encoding_to_cgt[] __initconst = {
>  	SR_TRAP(SYS_PMSIRR_EL1,		CGT_MDCR_TPMS),
>  	SR_TRAP(SYS_PMSLATFR_EL1,	CGT_MDCR_TPMS),
>  	SR_TRAP(SYS_PMSNEVFR_EL1,	CGT_MDCR_TPMS),
> +	SR_TRAP(SYS_PMSDSFR_EL1,	CGT_MDCR_TPMS),
>  	SR_TRAP(SYS_TRFCR_EL1,		CGT_MDCR_TTRF),
>  	SR_TRAP(SYS_TRBBASER_EL1,	CGT_MDCR_E2TB),
>  	SR_TRAP(SYS_TRBLIMITR_EL1,	CGT_MDCR_E2TB),
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index a6cf2888d150..4a88ba15c7df 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -3008,6 +3008,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	{ SYS_DESC(SYS_PMBLIMITR_EL1), undef_access },
>  	{ SYS_DESC(SYS_PMBPTR_EL1), undef_access },
>  	{ SYS_DESC(SYS_PMBSR_EL1), undef_access },
> +	{ SYS_DESC(SYS_PMSDSFR_EL1), undef_access },
>  	/* PMBIDR_EL1 is not trapped */
>  
>  	{ PMU_SYS_REG(PMINTENSET_EL1),
> 
> -- 
> 2.34.1
>