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Subject: Re: [PATCH v6 19/22] powerpc/book3s64/hash/kuap: Enable kuap on hash
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
 linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au
References: <20201125051634.509286-1-aneesh.kumar@linux.ibm.com>
 <20201125051634.509286-20-aneesh.kumar@linux.ibm.com>
From: Christophe Leroy <christophe.leroy@csgroup.eu>
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Date: Fri, 8 Oct 2021 11:32:03 +0200
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Cc: Sandipan Das <sandipan@linux.ibm.com>
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Le 25/11/2020 à 06:16, Aneesh Kumar K.V a écrit :
> Reviewed-by: Sandipan Das <sandipan@linux.ibm.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>   arch/powerpc/mm/book3s64/pkeys.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c
> index f747d66cc87d..84f8664ffc47 100644
> --- a/arch/powerpc/mm/book3s64/pkeys.c
> +++ b/arch/powerpc/mm/book3s64/pkeys.c
> @@ -257,7 +257,12 @@ void __init setup_kuep(bool disabled)
>   #ifdef CONFIG_PPC_KUAP
>   void __init setup_kuap(bool disabled)
>   {
> -	if (disabled || !early_radix_enabled())
> +	if (disabled)
> +		return;
> +	/*
> +	 * On hash if PKEY feature is not enabled, disable KUAP too.
> +	 */
> +	if (!early_radix_enabled() && !early_mmu_has_feature(MMU_FTR_PKEY))

pkey_early_init_devtree() bails out without setting MMU_FTR_PKEY with 
the following:

	/*
	 * Only P7 and above supports SPRN_AMR update with MSR[PR] = 1
	 */
	if (!early_cpu_has_feature(CPU_FTR_ARCH_206))
		return;



Why would it be impossible to do KUAP in that case ? KUAP doesn't 
require updating SPRN_AMR with MSR[PR] = 1


>   		return;
>   
>   	if (smp_processor_id() == boot_cpuid) {
>