linux-kernel - Re: HMM_MIRROR has less than useful help text

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Message-ID: <CAKTCnzkzvPgMK8i-cTuWFLRPPg4=DTkVQmS238VTgYJaUy=iVA@mail.gmail.com>
Date:   Thu, 18 Jul 2019 21:03:57 +1000
From:   Balbir Singh <bsingharora@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Jérôme Glisse <jglisse@...hat.com>,
        Evgeny Baskakov <ebaskakov@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Mark Hairgrove <mhairgrove@...dia.com>,
        Sherry Cheung <SCheung@...dia.com>,
        Subhash Gutti <sgutti@...dia.com>,
        Aneesh Kumar KV <aneesh.kumar@...ux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Dan Williams <dan.j.williams@...el.com>,
        David Nellans <dnellans@...dia.com>,
        Johannes Weiner <hannes@...xchg.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Michal Hocko <mhocko@...nel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Bob Liu <liubo95@...wei.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        kernel list <linux-kernel@...r.kernel.org>
Subject: Re: HMM_MIRROR has less than useful help text

On Wed, Jul 17, 2019 at 5:41 PM Pavel Machek <pavel@....cz> wrote:
>
> Hi!
>
> Commit c0b124054f9e42eb6da545a10fe9122a7d7c3f72 has very nice commit
> message, explaining what HMM_MIRROR is and when it is
> needed. Unfortunately, it did not make it into Kconfig help:
>
> CONFIG_HMM_MIRROR:
>
> Select HMM_MIRROR if you want to mirror range of the CPU page table of
> a
> process into a device page table. Here, mirror means "keep
> synchronized".
> Prerequisites: the device must provide the ability to write-protect
> its
> page tables (at PAGE_SIZE granularity), and must be able to recover
> from
> the resulting potential page faults.
>
> Could that be fixed?
>
> This is key information for me:
>
> # This is a heterogeneous memory management (HMM) process address space
> # mirroring.
> # This is useful for NVidia GPU >= Pascal, Mellanox IB >= mlx5 and more
> # hardware in the future.
>

That seems like a reasonable request

Balbir

> Thanks,
>                                                                 Pavel
> --
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html