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

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Message-ID: <CAPcyv4j=bZ5KBPp6PbViERdDe+HZpV_W6qbSJupTNAzyfiK6xg@mail.gmail.com>
Date:   Sat, 29 Feb 2020 14:33:08 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Logan Gunthorpe <logang@...tatee.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 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.

With that you can add:

Reviewed-by: Dan Williams <dan.j.williams@...el.com>