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Subject: Re: [PATCH 2/3] powerpc/64s/radix: ioremap use ioremap_page_range
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
References: <20190610030818.17965-1-npiggin@gmail.com>
 <20190610030818.17965-2-npiggin@gmail.com>
From: Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <1a9a36aa-f2bb-1ce8-78d5-ddf24e336078@c-s.fr>
Date: Tue, 11 Jun 2019 08:46:49 +0200
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Le 10/06/2019 à 05:08, Nicholas Piggin a écrit :
> Radix can use ioremap_page_range for ioremap, after slab is available.
> This makes it possible to enable huge ioremap mapping support.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   arch/powerpc/include/asm/book3s/64/radix.h |  3 +++
>   arch/powerpc/mm/book3s64/pgtable.c         | 21 +++++++++++++++++++++
>   arch/powerpc/mm/book3s64/radix_pgtable.c   | 21 +++++++++++++++++++++
>   arch/powerpc/mm/pgtable_64.c               |  2 +-
>   4 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/include/asm/book3s/64/radix.h b/arch/powerpc/include/asm/book3s/64/radix.h
> index 574eca33f893..e04a839cb5b9 100644
> --- a/arch/powerpc/include/asm/book3s/64/radix.h
> +++ b/arch/powerpc/include/asm/book3s/64/radix.h
> @@ -266,6 +266,9 @@ extern void radix__vmemmap_remove_mapping(unsigned long start,
>   extern int radix__map_kernel_page(unsigned long ea, unsigned long pa,
>   				 pgprot_t flags, unsigned int psz);
>   
> +extern int radix__ioremap_range(unsigned long ea, phys_addr_t pa,
> +				unsigned long size, pgprot_t prot, int nid);
> +

'extern' is pointless here, and checkpatch will cry.

>   static inline unsigned long radix__get_tree_size(void)
>   {
>   	unsigned long rts_field;
> diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
> index ff98b663c83e..953850a602f7 100644
> --- a/arch/powerpc/mm/book3s64/pgtable.c
> +++ b/arch/powerpc/mm/book3s64/pgtable.c
> @@ -450,3 +450,24 @@ int pmd_move_must_withdraw(struct spinlock *new_pmd_ptl,
>   
>   	return true;
>   }
> +
> +int ioremap_range(unsigned long ea, phys_addr_t pa, unsigned long size, pgprot_t prot, int nid)
> +{
> +	unsigned long i;
> +
> +	if (radix_enabled())
> +		return radix__ioremap_range(ea, pa, size, prot, nid);

This function looks pretty similar to the one in the previous patch.
Since radix_enabled() is available and return false for all other 
subarches, I think the above could go in the generic ioremap_range(), 
you'll only need to move the function declaration in a common file, for 
instance asm/io.h

> +
> +	for (i = 0; i < size; i += PAGE_SIZE) {
> +		int err = map_kernel_page(ea + i, pa + i, prot);
> +		if (err) {
> +			if (slab_is_available())
> +				unmap_kernel_range(ea, size);
> +			else
> +				WARN_ON_ONCE(1); /* Should clean up */
> +			return err;
> +		}
> +	}
> +
> +	return 0;
> +}
> diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
> index c9bcf428dd2b..db993bc1aef3 100644
> --- a/arch/powerpc/mm/book3s64/radix_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
> @@ -11,6 +11,7 @@
>   
>   #define pr_fmt(fmt) "radix-mmu: " fmt
>   
> +#include <linux/io.h>
>   #include <linux/kernel.h>
>   #include <linux/sched/mm.h>
>   #include <linux/memblock.h>
> @@ -1122,3 +1123,23 @@ void radix__ptep_modify_prot_commit(struct vm_area_struct *vma,
>   
>   	set_pte_at(mm, addr, ptep, pte);
>   }
> +
> +int radix__ioremap_range(unsigned long ea, phys_addr_t pa, unsigned long size,
> +			pgprot_t prot, int nid)
> +{
> +	if (likely(slab_is_available())) {
> +		int err = ioremap_page_range(ea, ea + size, pa, prot);
> +		if (err)
> +			unmap_kernel_range(ea, size);
> +		return err;
> +	} else {
> +		unsigned long i;
> +
> +		for (i = 0; i < size; i += PAGE_SIZE) {
> +			int err = map_kernel_page(ea + i, pa + i, prot);
> +			if (WARN_ON_ONCE(err)) /* Should clean up */
> +				return err;
> +		}

Same loop again.

What about not doing a radix specific function and just putting 
something like below in the core ioremap_range() function ?

	if (likely(slab_is_available()) && radix_enabled()) {
		int err = ioremap_page_range(ea, ea + size, pa, prot);

		if (err)
			unmap_kernel_range(ea, size);
		return err;
	}

Because I'm pretty sure will more and more use ioremap_page_range().

> +		return 0;
> +	}
> +}
> diff --git a/arch/powerpc/mm/pgtable_64.c b/arch/powerpc/mm/pgtable_64.c
> index 6bd3660388aa..63cd81130643 100644
> --- a/arch/powerpc/mm/pgtable_64.c
> +++ b/arch/powerpc/mm/pgtable_64.c
> @@ -108,7 +108,7 @@ unsigned long ioremap_bot;
>   unsigned long ioremap_bot = IOREMAP_BASE;
>   #endif
>   
> -static int ioremap_range(unsigned long ea, phys_addr_t pa, unsigned long size, pgprot_t prot, int nid)
> +int __weak ioremap_range(unsigned long ea, phys_addr_t pa, unsigned long size, pgprot_t prot, int nid)

Hum. Weak functions remain in unused in vmlinux unless 
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION is selected.

Also, they are some how dangerous because people might change them 
without seeing that it is overridden for some particular configuration.

Christophe

>   {
>   	unsigned long i;
>   
>