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

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Message-ID: <5729d03d6a174da6b66d1534ebdb1127@AcuMS.aculab.com>
Date:   Mon, 7 Mar 2022 22:11:19 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Christoph Hellwig' <hch@...radead.org>,
        Jarkko Sakkinen <jarkko@...nel.org>
CC:     Matthew Wilcox <willy@...radead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        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-sgx@...r.kernel.org>,
        "linux-kernel@...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>, "G@....fi" <G@....fi>,
        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" <linux-mips@...r.kernel.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "codalist@...a.cs.cmu.edu" <codalist@...a.cs.cmu.edu>,
        "linux-unionfs@...r.kernel.org" <linux-unionfs@...r.kernel.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
Subject: RE: [PATCH RFC 0/3] MAP_POPULATE for device memory

From: Christoph Hellwig
> Sent: 07 March 2022 15:57
> 
> On Mon, Mar 07, 2022 at 03:29:35PM +0200, Jarkko Sakkinen wrote:
> > So what would you suggest to sort out the issue? I'm happy to go with
> > ioctl if nothing else is acceptable.
> 
> PLenty of drivers treat all mmaps as if MAP_POPULATE was specified,
> typically by using (io_)remap_pfn_range.  If there any reason to only
> optionally have the pre-fault semantics for sgx?  If not this should
> be really simple.  And if we have a real need for it to be optional
> we'll just need to find a sane way to pass that information to ->mmap.

Is there any space in vma->vm_flags ?

That would be better than an extra argument or function.

	David

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