From: David Laight <David.Laight@ACULAB.COM>
To: 'Jarkko Sakkinen' <jarkko@kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Cc: "Dave Hansen" <dave.hansen@linux.intel.com>,
"Nathaniel McCallum" <nathaniel@profian.com>,
"Reinette Chatre" <reinette.chatre@intel.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"linux-sgx@vger.kernel.org" <linux-sgx@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Florian Fainelli" <f.fainelli@gmail.com>,
"Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
"Matthew Auld" <matthew.auld@intel.com>,
"Thomas Hellström" <thomas.hellstrom@linux.intel.com>,
"Daniel Vetter" <daniel.vetter@ffwll.ch>,
"Jason Ekstrand" <jason@jlekstrand.net>,
"Chris Wilson" <chris@chris-wilson.co.uk>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Tvrtko Ursulin" <tvrtko.ursulin@intel.com>,
"Vasily Averin" <vvs@virtuozzo.com>,
"Shakeel Butt" <shakeelb@google.com>,
"Michal Hocko" <mhocko@suse.com>,
zhangyiru <zhangyiru3@huawei.com>,
"Alexey Gladkov" <legion@kernel.org>,
"Alexander Mikhalitsyn" <alexander.mikhalitsyn@virtuozzo.com>,
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<intel-gfx@lists.freedesktop.org>,
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<dri-devel@lists.freedesktop.org>,
"codalist@coda.cs.cmu.edu" <codalist@coda.cs.cmu.edu>,
"linux-unionfs@vger.kernel.org" <linux-unionfs@vger.kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: RE: [PATCH RFC 0/3] MAP_POPULATE for device memory
Date: Sun, 6 Mar 2022 08:30:14 +0000 [thread overview]
Message-ID: <7f46ef3c80734f478501d21cef0182c5@AcuMS.aculab.com> (raw)
In-Reply-To: <20220306053211.135762-1-jarkko@kernel.org>
From: Jarkko Sakkinen
> Sent: 06 March 2022 05:32
>
> 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).
Is this all about trying to stop the vm_operations_struct.fault()
function being called?
It is pretty easy to ensure the mappings are setup in the driver's
mmap() function.
Then the fault() function can just return -VM_FAULT_SIGBUS;
If it is actually device memory you just need to call vm_iomap_memory()
That quite nicely mmap()s PCIe memory space into a user process.
Mapping driver memory is slightly more difficult.
For buffers allocated with dma_alloc_coherent() you can
probably use dma_mmap_coherent().
But I have a loop calling remap_pfn_range() because the
buffer area is made of multiple 16kB kernel buffers that
need to be mapped to contiguous user pages.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-03-06 8:30 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-06 5:32 [PATCH RFC 0/3] MAP_POPULATE for device memory Jarkko Sakkinen
2022-03-06 5:32 ` [PATCH RFC 1/3] mm: Add f_ops->populate() Jarkko Sakkinen
2022-03-06 10:01 ` Greg Kroah-Hartman
2022-03-06 17:02 ` Jarkko Sakkinen
2022-03-06 17:03 ` Jarkko Sakkinen
2022-03-06 22:43 ` Matthew Wilcox
2022-03-07 13:16 ` Jarkko Sakkinen
2022-03-07 13:26 ` Jarkko Sakkinen
2022-03-06 5:32 ` [PATCH RFC 2/3] x86/sgx: Export sgx_encl_page_alloc() Jarkko Sakkinen
2022-03-06 5:32 ` [PATCH RFC 3/3] x86/sgx: Implement EAUG population with MAP_POPULATE Jarkko Sakkinen
2022-03-06 8:30 ` David Laight [this message]
2022-03-06 16:52 ` [PATCH RFC 0/3] MAP_POPULATE for device memory 'Jarkko Sakkinen'
2022-03-06 11:33 ` Matthew Wilcox
2022-03-07 7:48 ` Christoph Hellwig
2022-03-07 13:29 ` Jarkko Sakkinen
2022-03-07 15:56 ` Christoph Hellwig
2022-03-07 15:58 ` Jarkko Sakkinen
2022-03-07 22:11 ` David Laight
2022-03-08 10:10 ` Jarkko Sakkinen
2022-03-07 10:12 ` David Hildenbrand
2022-03-07 14:22 ` Jarkko Sakkinen
2022-03-07 14:33 ` David Hildenbrand
2022-03-07 15:49 ` Jarkko Sakkinen
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