linux-kernel - Re: [PATCH RFC 0/3] MAP_POPULATE for device memory

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Message-ID: <d6b09f23-f470-c119-8d3e-7d72a3448b64@redhat.com>
Date:   Mon, 7 Mar 2022 11:12:44 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>, linux-mm@...ck.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Nathaniel McCallum <nathaniel@...fian.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-sgx@...r.kernel.org, linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Matthew Auld <matthew.auld@...el.com>,
        Thomas Hellström 
        <thomas.hellstrom@...ux.intel.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jason Ekstrand <jason@...kstrand.net>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Vasily Averin <vvs@...tuozzo.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        zhangyiru <zhangyiru3@...wei.com>,
        Alexey Gladkov <legion@...nel.org>,
        Alexander Mikhalitsyn <alexander.mikhalitsyn@...tuozzo.com>,
        linux-mips@...r.kernel.org, intel-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, codalist@...a.cs.cmu.edu,
        linux-unionfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH RFC 0/3] MAP_POPULATE for device memory

On 06.03.22 06:32, Jarkko Sakkinen wrote:
> For device memory (aka VM_IO | VM_PFNMAP) MAP_POPULATE does nothing. Allow
> to use that for initializing the device memory by providing a new callback
> f_ops->populate() for the purpose.
> 
> SGX patches are provided to show the callback in context.
> 
> An obvious alternative is a ioctl but it is less elegant and requires
> two syscalls (mmap + ioctl) per memory range, instead of just one
> (mmap).

What about extending MADV_POPULATE_READ | MADV_POPULATE_WRITE to support
VM_IO | VM_PFNMAP (as well?) ?


-- 
Thanks,

David / dhildenb