linux-kernel - Re: [PATCH v3 4/7] x86/mm: Introduce _set_memory

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Date:   Mon, 2 Mar 2020 11:46:13 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-ia64@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Linux-sh <linux-sh@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        Michal Hocko <mhocko@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Eric Badger <ebadger@...aio.com>,
        "H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH v3 4/7] x86/mm: Introduce _set_memory_prot()



On 2020-02-29 3:33 p.m., Dan Williams wrote:
> On Fri, Feb 21, 2020 at 10:25 AM Logan Gunthorpe <logang@...tatee.com> wrote:
>>
>> For use in the 32bit arch_add_memory() to set the pgprot type of the
>> memory to add.
>>
>> Cc: Thomas Gleixner <tglx@...utronix.de>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Borislav Petkov <bp@...en8.de>
>> Cc: "H. Peter Anvin" <hpa@...or.com>
>> Cc: x86@...nel.org
>> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
>> Cc: Andy Lutomirski <luto@...nel.org>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
>> ---
>>  arch/x86/include/asm/set_memory.h | 1 +
>>  arch/x86/mm/pat/set_memory.c      | 7 +++++++
>>  2 files changed, 8 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/set_memory.h b/arch/x86/include/asm/set_memory.h
>> index 64c3dce374e5..0aca959cf9a4 100644
>> --- a/arch/x86/include/asm/set_memory.h
>> +++ b/arch/x86/include/asm/set_memory.h
>> @@ -34,6 +34,7 @@
>>   * The caller is required to take care of these.
>>   */
>>
>> +int _set_memory_prot(unsigned long addr, int numpages, pgprot_t prot);
> 
> I wonder if this should be separated from the naming convention of the
> other routines because this is only an internal helper for code paths
> where the prot was established by an upper layer. For example, I
> expect that the kernel does not want new usages to make the mistake of
> calling:
> 
>    _set_memory_prot(..., pgprot_writecombine(pgprot))
> 
> ...instead of
> 
>     _set_memory_wc()
> 
> I'm thinking just a double underscore rename (__set_memory_prot) and a
> kerneldoc comment for that  pointing people to use the direct
> _set_memory_<cachemode> helpers.

Thanks! Will do. Note, though, that even _set_memory_wc() is an internal
x86-specific function. But the extra comment and underscore still make
sense.

> With that you can add:
> 
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
>