linux-kernel - Re: [PATCH 1/2] powerpc: Refactor __kernel_map

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Date: Thu, 22 Feb 2024 07:59:34 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH 1/2] powerpc: Refactor __kernel_map_pages()



Le 22/02/2024 à 06:32, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@...roup.eu> writes:
>> __kernel_map_pages() is almost identical for PPC32 and RADIX.
>>
>> Refactor it.
>>
>> On PPC32 it is not needed for KFENCE, but to keep it simple
>> just make it similar to PPC64.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
>> ---
>>   arch/powerpc/include/asm/book3s/64/pgtable.h | 10 ----------
>>   arch/powerpc/include/asm/book3s/64/radix.h   |  2 --
>>   arch/powerpc/mm/book3s64/radix_pgtable.c     | 14 --------------
>>   arch/powerpc/mm/pageattr.c                   | 19 +++++++++++++++++++
>>   arch/powerpc/mm/pgtable_32.c                 | 15 ---------------
>>   5 files changed, 19 insertions(+), 41 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
>> index 421db7c4f2a4..16b8d20d6ca8 100644
>> --- a/arch/powerpc/mm/pageattr.c
>> +++ b/arch/powerpc/mm/pageattr.c
>> @@ -101,3 +101,22 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
>>   	return apply_to_existing_page_range(&init_mm, start, size,
>>   					    change_page_attr, (void *)action);
>>   }
>> +
>> +#if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_KFENCE)
>> +#ifdef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
>> +void __kernel_map_pages(struct page *page, int numpages, int enable)
>> +{
>> +	unsigned long addr = (unsigned long)page_address(page);
>> +
>> +	if (PageHighMem(page))
>> +		return;
>> +
>> +	if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !radix_enabled())
>> +		hash__kernel_map_pages(page, numpages, enable);
>> +	else if (enable)
>> +		set_memory_p(addr, numpages);
>> +	else
>> +		set_memory_np(addr, numpages);
>> +}
> 
> This doesn't build on 32-bit, eg. ppc32_allmodconfig:
> 
> ../arch/powerpc/mm/pageattr.c: In function '__kernel_map_pages':
> ../arch/powerpc/mm/pageattr.c:116:23: error: implicit declaration of function 'hash__kernel_map_pages' [-Werror=implicit-function-declaration]
>    116 |                 err = hash__kernel_map_pages(page, numpages, enable);
>        |                       ^~~~~~~~~~~~~~~~~~~~~~
> 
> I couldn't see a nice way to get around it, so ended up with:
> 
> void __kernel_map_pages(struct page *page, int numpages, int enable)
> {
> 	int err;
> 	unsigned long addr = (unsigned long)page_address(page);
> 
> 	if (PageHighMem(page))
> 		return;
> 
> #ifdef CONFIG_PPC_BOOK3S_64
> 	if (!radix_enabled())
> 		err = hash__kernel_map_pages(page, numpages, enable);
> 	else
> #endif
> 	if (enable)
> 		err = set_memory_p(addr, numpages);
> 	else
> 		err = set_memory_np(addr, numpages);
> 


I missed something it seems. Not good to leave something unterminated 
when you leave for vacation and think it was finished when you come back.

The best solution I see is to move hash__kernel_map_pages() prototype 
somewhere else.

$ git grep -e hash__ -e radix__ -- arch/powerpc/include/asm/*.h
arch/powerpc/include/asm/bug.h:void hash__do_page_fault(struct pt_regs *);
arch/powerpc/include/asm/mmu.h:extern void radix__mmu_cleanup_all(void);
arch/powerpc/include/asm/mmu_context.h:extern void 
radix__switch_mmu_context(struct mm_struct *prev,
arch/powerpc/include/asm/mmu_context.h:         return 
radix__switch_mmu_context(prev, next);
arch/powerpc/include/asm/mmu_context.h:extern int 
hash__alloc_context_id(void);
arch/powerpc/include/asm/mmu_context.h:void __init 
hash__reserve_context_id(int id);
arch/powerpc/include/asm/mmu_context.h: context_id = 
hash__alloc_context_id();
arch/powerpc/include/asm/mmu_context.h:  * radix__flush_all_mm() to 
determine the scope (local/global)
arch/powerpc/include/asm/mmu_context.h:         radix__flush_all_mm(mm);


Maybe asm/mmu.h ?

Or mm/mmu_decl.h ?

Christophe