linux-kernel - Re: [PATCH v1 5/5] arm64/config: add config to control whether enable HDBSS feature

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Message-ID: <86v7sfopvl.wl-maz@kernel.org>
Date: Tue, 11 Mar 2025 09:53:02 +0000
From: Marc Zyngier <maz@...nel.org>
To: Zhenyu Ye <yezhenyu2@...wei.com>
Cc: <yuzenghui@...wei.com>,
	<will@...nel.org>,
	<oliver.upton@...ux.dev>,
	<catalin.marinas@....com>,
	<joey.gouly@....com>,
	<linux-kernel@...r.kernel.org>,
	<xiexiangyou@...wei.com>,
	<zhengchuan@...wei.com>,
	<wangzhou1@...ilicon.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<kvm@...r.kernel.org>,
	<kvmarm@...ts.linux.dev>
Subject: Re: [PATCH v1 5/5] arm64/config: add config to control whether enable HDBSS feature

On Tue, 11 Mar 2025 04:03:21 +0000,
Zhenyu Ye <yezhenyu2@...wei.com> wrote:
> 
> From: eillon <yezhenyu2@...wei.com>
> 
> The HDBSS feature introduces new assembly registers
> (HDBSSBR_EL2 and HDBSSPROD_EL2), which depends on the armv9.5-a
> compilation support. So add ARM64_HDBSS config to control whether
> enable the HDBSS feature.
> 
> Signed-off-by: eillon <yezhenyu2@...wei.com>
> ---
>  arch/arm64/Kconfig                  | 19 +++++++++++++++++++
>  arch/arm64/Makefile                 |  4 +++-
>  arch/arm64/include/asm/cpufeature.h |  3 +++
>  3 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 940343beb3d4..3458261eb14b 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -2237,6 +2237,25 @@ config ARM64_GCS
>  
>  endmenu # "v9.4 architectural features"
>  
> +menu "ARMv9.5 architectural features"
> +
> +config ARM64_HDBSS
> +	bool "Enable support for Hardware Dirty state tracking Structure (HDBSS)"
> +	default y
> +	depends on AS_HAS_ARMV9_5
> +	help
> +	  Hardware Dirty state tracking Structure(HDBSS) enhances tracking
> +	  translation table descriptors’ dirty state to reduce the cost of
> +	  surveying for dirtied granules.
> +
> +	  The feature introduces new assembly registers (HDBSSBR_EL2 and
> +	  HDBSSPROD_EL2), which depends on AS_HAS_ARMV9_5.

Why? You seem to be using the generated accessors everywhere, and I
can't see a need for this compiler dependency.

	M.

-- 
Without deviation from the norm, progress is not possible.