linux-kernel - Re: [PATCH v1 2/6] powerpc/8xx: Always pin kernel text TLB

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Date:   Wed, 09 Dec 2020 21:43:12 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v1 2/6] powerpc/8xx: Always pin kernel text TLB

Christophe Leroy <christophe.leroy@...roup.eu> writes:
> There is no big poing in not pinning kernel text anymore, as now
> we can keep pinned TLB even with things like DEBUG_PAGEALLOC.
>
> Remove CONFIG_PIN_TLB_TEXT, making it always right.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> ---
>  arch/powerpc/Kconfig               |  3 +--
>  arch/powerpc/kernel/head_8xx.S     | 20 +++-----------------
>  arch/powerpc/mm/nohash/8xx.c       |  3 +--
>  arch/powerpc/platforms/8xx/Kconfig |  7 -------
>  4 files changed, 5 insertions(+), 28 deletions(-)
>
...
> diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
> index 231ca95f9ffb..19a3eec1d8c5 100644
> --- a/arch/powerpc/mm/nohash/8xx.c
> +++ b/arch/powerpc/mm/nohash/8xx.c
> @@ -186,8 +186,7 @@ void mmu_mark_initmem_nx(void)
>  	mmu_mapin_ram_chunk(0, boundary, PAGE_KERNEL_TEXT, false);
>  	mmu_mapin_ram_chunk(boundary, einittext8, PAGE_KERNEL, false);
>  
> -	if (IS_ENABLED(CONFIG_PIN_TLB_TEXT))
> -		mmu_pin_tlb(block_mapped_ram, false);
> +	mmu_pin_tlb(block_mapped_ram, false);
>  }

This broke mpc885_ads_defconfig with:

  ld: arch/powerpc/mm/nohash/8xx.o: in function `mmu_mark_initmem_nx':
  /home/michael/linux/arch/powerpc/mm/nohash/8xx.c:189: undefined reference to `mmu_pin_tlb'
  make[1]: *** [/home/michael/linux/Makefile:1164: vmlinux] Error 1
  make: *** [Makefile:185: __sub-make] Error 2

Fixed by:

diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 35707e86c5f3..52702f3db6df 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -702,7 +702,6 @@ FixupDAR:/* Entry point for dcbx workaround. */
 	mtspr	SPRN_DER, r8
 	blr
 
-#ifdef CONFIG_PIN_TLB
 _GLOBAL(mmu_pin_tlb)
 	lis	r9, (1f - PAGE_OFFSET)@h
 	ori	r9, r9, (1f - PAGE_OFFSET)@l
@@ -802,7 +801,6 @@ _GLOBAL(mmu_pin_tlb)
 	mtspr	SPRN_SRR1, r10
 	mtspr	SPRN_SRR0, r11
 	rfi
-#endif /* CONFIG_PIN_TLB */
 
 /*
  * We put a few things here that have to be page-aligned.


cheers