linux-kernel - Re: [PATCH v2 2/2] powerpc/8xx: Map a second 8M text page at startup when needed.

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Date:   Wed, 13 Feb 2019 13:05:34 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] powerpc/8xx: Map a second 8M text page at startup
 when needed.


Le 21/01/2019 à 12:34, Christophe Leroy a écrit :
> Some debug setup like CONFIG_KASAN generate huge
> kernels with text size over the 8M limit.
> 
> This patch maps a second 8M page when _einittext is over 8M.

This is not enough for CONFIG_KASAN_INLINE. I'll send a v3 which maps up 
to 32M based on _einittext.


> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> ---
>   v2: Using IS_ENABLED() instead of #ifdef in 8xx_mmu.c
> 
>   arch/powerpc/kernel/head_8xx.S | 27 +++++++++++++++++++++++++--
>   arch/powerpc/mm/8xx_mmu.c      |  3 +++
>   2 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
> index 20cc816b3508..3b3b7846247f 100644
> --- a/arch/powerpc/kernel/head_8xx.S
> +++ b/arch/powerpc/kernel/head_8xx.S
> @@ -337,8 +337,8 @@ InstructionTLBMiss:
>   	rlwinm	r10, r10, 16, 0xfff8
>   	cmpli	cr0, r10, PAGE_OFFSET@h
>   #ifndef CONFIG_PIN_TLB_TEXT
> -	/* It is assumed that kernel code fits into the first 8M page */
> -0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x0800000)@h
> +	/* It is assumed that kernel code fits into the two first 8M pages */
> +0:	cmpli	cr7, r10, (PAGE_OFFSET + 0x1000000)@h
>   	patch_site	0b, patch__itlbmiss_linmem_top
>   #endif
>   #endif
> @@ -908,6 +908,29 @@ initial_mmu:
>   	li	r8, MI_BOOTINIT		/* Create RPN for address 0 */
>   	mtspr	SPRN_MI_RPN, r8		/* Store TLB entry */
>   
> +	/* Map a second 8M page if needed */
> +	lis	r9, _einittext@h
> +	oris	r9, r9, _einittext@l
> +	cmpli	cr0, r9, (PAGE_OFFSET + 0x8000000)@h

Should be 0x800000 here

Christophe

> +	blt	1f
> +
> +#ifdef CONFIG_PIN_TLB_TEXT
> +	lis	r8, MI_RSV4I@h
> +	ori	r8, r8, 0x1d00
> +
> +	mtspr	SPRN_MI_CTR, r8	/* Set instruction MMU control */
> +#endif
> +
> +	lis	r8, (KERNELBASE + 0x800000)@h	/* Create vaddr for TLB */
> +	ori	r8, r8, MI_EVALID	/* Mark it valid */
> +	mtspr	SPRN_MI_EPN, r8
> +	li	r8, MI_PS8MEG /* Set 8M byte page */
> +	ori	r8, r8, MI_SVALID	/* Make it valid */
> +	mtspr	SPRN_MI_TWC, r8
> +	li	r8, MI_BOOTINIT		/* Create RPN for address 0 */
> +	addis	r8, r8, 0x80
> +	mtspr	SPRN_MI_RPN, r8		/* Store TLB entry */
> +1:
>   	lis	r8, MI_APG_INIT@h	/* Set protection modes */
>   	ori	r8, r8, MI_APG_INIT@l
>   	mtspr	SPRN_MI_AP, r8
> diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c
> index 92b677faea8c..b5f6d794281d 100644
> --- a/arch/powerpc/mm/8xx_mmu.c
> +++ b/arch/powerpc/mm/8xx_mmu.c
> @@ -112,6 +112,9 @@ unsigned long __init mmu_mapin_ram(unsigned long top)
>   			mmu_patch_cmp_limit(&patch__itlbmiss_linmem_top, 0);
>   	} else {
>   		mapped = top & ~(LARGE_PAGE_SIZE_8M - 1);
> +		if (!IS_ENABLED(CONFIG_PIN_TLB_TEXT))
> +			mmu_patch_cmp_limit(&patch__itlbmiss_linmem_top,
> +					    _ALIGN(__pa(_einittext), 8 << 20));
>   	}
>   
>   	mmu_patch_cmp_limit(&patch__dtlbmiss_linmem_top, mapped);
>