linux-kernel - Re: [PATCH v13 06/14] mm: HUGE

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Message-ID: <ad8138dd-3b99-bb76-3257-2d959f770d4b@csgroup.eu>
Date:   Wed, 28 Apr 2021 10:34:28 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Nicholas Piggin <npiggin@...il.com>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Christoph Hellwig <hch@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Ding Tianhong <dingtianhong@...wei.com>,
        linuxppc-dev@...ts.ozlabs.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v13 06/14] mm: HUGE_VMAP arch support cleanup



Le 28/04/2021 à 10:32, Christophe Leroy a écrit :
> 
> 
> Le 17/03/2021 à 07:23, Nicholas Piggin a écrit :
>> This changes the awkward approach where architectures provide init
>> functions to determine which levels they can provide large mappings for,
>> to one where the arch is queried for each call.
>>
>> This removes code and indirection, and allows constant-folding of dead
>> code for unsupported levels.
>>
>> This also adds a prot argument to the arch query. This is unused
>> currently but could help with some architectures (e.g., some powerpc
>> processors can't map uncacheable memory with large pages).
>>
>> Cc: linuxppc-dev@...ts.ozlabs.org
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Borislav Petkov <bp@...en8.de>
>> Cc: x86@...nel.org
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Reviewed-by: Ding Tianhong <dingtianhong@...wei.com>
>> Acked-by: Catalin Marinas <catalin.marinas@....com> [arm64]
>> Signed-off-by: Nicholas Piggin <npiggin@...il.com>
>> ---
>>   arch/arm64/include/asm/vmalloc.h         |  8 ++
>>   arch/arm64/mm/mmu.c                      | 10 +--
>>   arch/powerpc/include/asm/vmalloc.h       |  8 ++
>>   arch/powerpc/mm/book3s64/radix_pgtable.c |  8 +-
>>   arch/x86/include/asm/vmalloc.h           |  7 ++
>>   arch/x86/mm/ioremap.c                    | 12 +--
>>   include/linux/io.h                       |  9 ---
>>   include/linux/vmalloc.h                  |  6 ++
>>   init/main.c                              |  1 -
>>   mm/debug_vm_pgtable.c                    |  4 +-
>>   mm/ioremap.c                             | 94 ++++++++++--------------
>>   11 files changed, 87 insertions(+), 80 deletions(-)
>>
> 
>> diff --git a/mm/ioremap.c b/mm/ioremap.c
>> index 3f4d36f9745a..3264d0203785 100644
>> --- a/mm/ioremap.c
>> +++ b/mm/ioremap.c
>> @@ -16,49 +16,16 @@
>>   #include "pgalloc-track.h"
>>   #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
>> -static int __read_mostly ioremap_p4d_capable;
>> -static int __read_mostly ioremap_pud_capable;
>> -static int __read_mostly ioremap_pmd_capable;
>> -static int __read_mostly ioremap_huge_disabled;
>> +static bool __ro_after_init iomap_max_page_shift = PAGE_SHIFT;
> 
> Must be an int, not a bool.

And the initial value seems wrong. Should be P4D_SHIFT ?

> 
>>   static int __init set_nohugeiomap(char *str)
>>   {
>> -    ioremap_huge_disabled = 1;
>> +    iomap_max_page_shift = P4D_SHIFT;

And PAGE_SHIFT here when NO hugeiomap ?

>>       return 0;
>>   }
>>   early_param("nohugeiomap", set_nohugeiomap);

Christophe