linux-kernel - Re: [PATCH] powerpc/32s: fix BATs setting with CONFIG_STRICT_KERNEL

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Date:   Mon, 29 Apr 2019 07:03:22 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Serge Belyshev <belyshev@...ni.sinp.msu.ru>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] powerpc/32s: fix BATs setting with CONFIG_STRICT_KERNEL_RWX

Acked-by: Segher Boessenkool <segher@...nel.crashing.org>

(But see comments below.)

On Mon, Apr 29, 2019 at 09:08:09AM +0000, Christophe Leroy wrote:
> diff --git a/arch/powerpc/mm/ppc_mmu_32.c b/arch/powerpc/mm/ppc_mmu_32.c
> index bf1de3ca39bc..37cf2af98f6a 100644
> --- a/arch/powerpc/mm/ppc_mmu_32.c
> +++ b/arch/powerpc/mm/ppc_mmu_32.c
> @@ -101,7 +101,7 @@ static int find_free_bat(void)
>  static unsigned int block_size(unsigned long base, unsigned long top)
>  {
>  	unsigned int max_size = (cpu_has_feature(CPU_FTR_601) ? 8 : 256) << 20;
> -	unsigned int base_shift = (fls(base) - 1) & 31;
> +	unsigned int base_shift = (ffs(base) - 1) & 31;
>  	unsigned int block_shift = (fls(top - base) - 1) & 31;

The code is quite confusing now...  Add a comment, or improve it?


Segher