linux-kernel - Re: [PATCH] mm/Kconfig: additional help text for HMM

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Date:   Thu, 18 Jul 2019 22:57:48 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     john.hubbard@...il.com
Cc:     pavel@....cz, SCheung@...dia.com, akpm@...ux-foundation.org,
        aneesh.kumar@...ux.vnet.ibm.com, benh@...nel.crashing.org,
        bsingharora@...il.com, dan.j.williams@...el.com,
        dnellans@...dia.com, ebaskakov@...dia.com, hannes@...xchg.org,
        jglisse@...hat.com, jhubbard@...dia.com,
        kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org,
        liubo95@...wei.com, mhairgrove@...dia.com, mhocko@...nel.org,
        paulmck@...ux.vnet.ibm.com, ross.zwisler@...ux.intel.com,
        sgutti@...dia.com, torvalds@...ux-foundation.org,
        vdavydov.dev@...il.com, Jason Gunthorpe <jgg@...pe.ca>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] mm/Kconfig: additional help text for HMM_MIRROR option

On Thu, Jul 18, 2019 at 06:32:53PM -0700, john.hubbard@...il.com wrote:
> +	  HMM_MIRROR provides a way to mirror ranges of the CPU page tables
> +	  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.
> +
> +	  Select HMM_MIRROR if you have hardware that meets the above
> +	  description. An early, partial list of such hardware is:
> +	  an NVIDIA GPU >= Pascal, Mellanox IB >= mlx5, or an AMD GPU.

Nevermind that the Nvidia support is stagaging and looks rather broken,
there is no Mellanox user of this either at this point.

But either way this has no business in a common kconfig help.  Just
drop the fine grained details and leave it to the overview.