Subject: Re: [PATCH] powerpc/mm: Fix lazy icache flush on pre-POWER5

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Tue, 29 Nov 2016 08:25:37 +0530

Benjamin Herrenschmidt <[email-masked]> writes:

> On 64-bit CPUs with no-execute support and non-snooping icache, such as
> 970 or POWER4, we have a software mechanism to ensure coherency of the
> cache (using exec faults when needed).
>
> This was broken due to a logic inversion when that code was rewritten
> from assembly to C.

The asm code for reference is

BEGIN_FTR_SECTION
       mr      r4,r30
       mr      r5,r7
       bl      hash_page_do_lazy_icache
END_FTR_SECTION(CPU_FTR_NOEXECUTE|CPU_FTR_COHERENT_ICACHE, CPU_FTR_NOEXECUTE)

Reviewed-by: Aneesh Kumar K.V <[email-masked]>

>
> Signed-off-by: Benjamin Herrenschmidt <[email-masked]>
> Fixes: 91f1da99792a1d133df94c4753510305353064a1
> Fixes: 89ff725051d177556b23d80f2a30f880a657a6c1
> Fixes: a43c0eb8364c022725df586e91dd753633374d66
> --
> diff --git a/arch/powerpc/mm/hash64_4k.c b/arch/powerpc/mm/hash64_4k.c
> index 42c702b..6fa450c 100644
> --- a/arch/powerpc/mm/hash64_4k.c
> +++ b/arch/powerpc/mm/hash64_4k.c
> @@ -55,7 +55,7 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
>  	 */
>  	rflags = htab_convert_pte_flags(new_pte);
>
> -	if (!cpu_has_feature(CPU_FTR_NOEXECUTE) &&
> +	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
>  	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
>  		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
>
> diff --git a/arch/powerpc/mm/hash64_64k.c b/arch/powerpc/mm/hash64_64k.c
> index 3bbbea0..1a68cb1 100644
> --- a/arch/powerpc/mm/hash64_64k.c
> +++ b/arch/powerpc/mm/hash64_64k.c
> @@ -87,7 +87,7 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
>  	subpg_pte = new_pte & ~subpg_prot;
>  	rflags = htab_convert_pte_flags(subpg_pte);
>
> -	if (!cpu_has_feature(CPU_FTR_NOEXECUTE) &&
> +	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
>  	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) {
>
>  		/*
> @@ -258,7 +258,7 @@ int __hash_page_64K(unsigned long ea, unsigned long access,
>
>  	rflags = htab_convert_pte_flags(new_pte);
>
> -	if (!cpu_has_feature(CPU_FTR_NOEXECUTE) &&
> +	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
>  	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
>  		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);