[RFC 02/12] arm64: Detect FEAT_TLBID

[Linu Cherian]

Hi,

On Thu, Oct 01, 2026 at 12:06:45PM +0100, Kristina Martšenko wrote:
> Detect if FEAT_TLBID is supported by the system. Detect TLBID
> configuration from TLBIDIDR_EL1. This information will be used in later
> patches.
> 
> Set HFGRTR2_EL2.nTLBIDIDR_EL1 so that the kernel can access TLBIDIDR_EL1
> at EL1 (in case of nVHE/hVHE).
> 
> Signed-off-by: Kristina Martšenko <kristina.martsenko at arm.com>
> ---
>  arch/arm64/include/asm/cpu.h        |  1 +
>  arch/arm64/include/asm/cpufeature.h |  7 +++++++
>  arch/arm64/include/asm/el2_setup.h  |  9 ++++++++-
>  arch/arm64/kernel/cpufeature.c      | 25 +++++++++++++++++++++++++
>  arch/arm64/kernel/cpuinfo.c         |  3 +++
>  arch/arm64/tools/cpucaps            |  1 +
>  6 files changed, 45 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/cpu.h b/arch/arm64/include/asm/cpu.h
> index 3c008821219c..967ccdedf526 100644
> --- a/arch/arm64/include/asm/cpu.h
> +++ b/arch/arm64/include/asm/cpu.h
> @@ -48,6 +48,7 @@ struct cpuinfo_arm64 {
>  	u64		reg_gmid;
>  	u64		reg_smidr;
>  	u64		reg_mpamidr;
> +	u64		reg_tlbididr;
>  
>  	u64		reg_id_aa64dfr0;
>  	u64		reg_id_aa64dfr1;
> diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
> index 4f04ad82ea34..d4e7497143b2 100644
> --- a/arch/arm64/include/asm/cpufeature.h
> +++ b/arch/arm64/include/asm/cpufeature.h
> @@ -627,6 +627,13 @@ static inline bool id_aa64pfr1_mpamfrac(u64 pfr1)
>  	return val > 0;
>  }
>  
> +static inline bool id_aa64mmfr4_tlbid(u64 mmfr4)
> +{
> +	u32 val = cpuid_feature_extract_unsigned_field(mmfr4, ID_AA64MMFR4_EL1_TLBID_SHIFT);
> +
> +	return val > 0;
> +}
> +
>  void __init setup_boot_cpu_features(void);
>  void __init setup_system_features(void);
>  void __init setup_user_features(void);
> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
> index aa8ec9df8024..bd70a470596c 100644
> --- a/arch/arm64/include/asm/el2_setup.h
> +++ b/arch/arm64/include/asm/el2_setup.h
> @@ -438,9 +438,16 @@
>  	orr	x0, x0, #HDFGRTR2_EL2_nPMSDSFR_EL1
>  
>  .Lskip_spefds_\@:
> +	mov	x1, xzr
> +	mrs_s	x2, SYS_ID_AA64MMFR4_EL1
> +	ubfx	x2, x2, #ID_AA64MMFR4_EL1_TLBID_SHIFT, #ID_AA64MMFR4_EL1_TLBID_WIDTH
> +	cbz	x2, .Lskip_tlbid_\@
> +	orr	x1, x1, #HFGRTR2_EL2_nTLBIDIDR_EL1
> +
> +.Lskip_tlbid_\@:
>  	msr_s   SYS_HDFGRTR2_EL2, x0
>  	msr_s   SYS_HDFGWTR2_EL2, x0
> -	msr_s   SYS_HFGRTR2_EL2, xzr
> +	msr_s   SYS_HFGRTR2_EL2, x1
>  	msr_s   SYS_HFGWTR2_EL2, xzr
>  	msr_s   SYS_HFGITR2_EL2, xzr
>  .Lskip_fgt2_\@:

IMO, would be good to move the above changes into a separate patch.

Thanks,
Linu Cherian.