From: "Christian König" <christian.koenig@amd.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: "Thomas Hellström (Intel)" <thomas_os@shipmail.org>,
"David Airlie" <airlied@linux.ie>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-mm@kvack.org, "Andrew Morton" <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages
Date: Thu, 25 Mar 2021 14:05:14 +0100 [thread overview]
Message-ID: <00f79bae-75c4-d694-8dc9-35ac21cd1006@amd.com> (raw)
In-Reply-To: <20210325124206.GA599656@nvidia.com>
Am 25.03.21 um 13:42 schrieb Jason Gunthorpe:
> On Thu, Mar 25, 2021 at 01:09:14PM +0100, Christian König wrote:
>> Am 25.03.21 um 13:01 schrieb Jason Gunthorpe:
>>> On Thu, Mar 25, 2021 at 12:53:15PM +0100, Thomas Hellström (Intel) wrote:
>>>
>>>> Nope. The point here was that in this case, to make sure mmap uses the
>>>> correct VA to give us a reasonable chance of alignement, the driver might
>>>> need to be aware of and do trickery with the huge page-table-entry sizes
>>>> anyway, although I think in most cases a standard helper for this can be
>>>> supplied.
>>> Of course the driver needs some way to influence the VA mmap uses,
>>> gernally it should align to the natural page size of the device
>> Well a mmap() needs to be aligned to the page size of the CPU, but not
>> necessarily to the one of the device.
>>
>> So I'm pretty sure the device driver should not be involved in any way the
>> choosing of the VA for the CPU mapping.
> No, if the device wants to use huge pages it must influence the mmap
> VA or it can't form huge pgaes.
No, that's the job of the core MM and not of the individual driver.
In other words current->mm->get_unmapped_area should already return a
properly aligned VA.
Messing with that inside file->f_op->get_unmapped_area is utterly
nonsense as far as I can see.
It happens to be this way currently, but that is not even remotely good
design.
Christian.
>
> It is the same reason why mmap returns 2M stuff these days to make THP
> possible
>
> Jason
next prev parent reply other threads:[~2021-03-25 13:06 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-21 18:45 [RFC PATCH 0/2] mm,drm/ttm: Always block GUP to TTM pages Thomas Hellström (Intel)
2021-03-21 18:45 ` [RFC PATCH 1/2] mm,drm/ttm: Block fast GUP to TTM huge pages Thomas Hellström (Intel)
2021-03-23 11:34 ` Daniel Vetter
2021-03-23 16:34 ` Thomas Hellström (Intel)
2021-03-23 16:37 ` Jason Gunthorpe
2021-03-23 16:59 ` Christoph Hellwig
2021-03-23 17:06 ` Thomas Hellström (Intel)
2021-03-24 9:56 ` Daniel Vetter
2021-03-24 12:24 ` Jason Gunthorpe
2021-03-24 12:35 ` Thomas Hellström (Intel)
2021-03-24 12:41 ` Jason Gunthorpe
2021-03-24 13:35 ` Thomas Hellström (Intel)
2021-03-24 13:48 ` Jason Gunthorpe
2021-03-24 15:50 ` Thomas Hellström (Intel)
2021-03-24 16:38 ` Jason Gunthorpe
2021-03-24 18:31 ` Christian König
2021-03-24 20:07 ` Thomas Hellström (Intel)
2021-03-24 23:14 ` Jason Gunthorpe
2021-03-25 7:48 ` Thomas Hellström (Intel)
2021-03-25 8:27 ` Christian König
2021-03-25 9:51 ` Thomas Hellström (Intel)
2021-03-25 11:30 ` Jason Gunthorpe
2021-03-25 11:53 ` Thomas Hellström (Intel)
2021-03-25 12:01 ` Jason Gunthorpe
2021-03-25 12:09 ` Christian König
2021-03-25 12:36 ` Thomas Hellström (Intel)
2021-03-25 13:02 ` Christian König
2021-03-25 13:31 ` Thomas Hellström (Intel)
2021-03-25 12:42 ` Jason Gunthorpe
2021-03-25 13:05 ` Christian König [this message]
2021-03-25 13:17 ` Jason Gunthorpe
2021-03-25 13:26 ` Christian König
2021-03-25 13:33 ` Jason Gunthorpe
2021-03-25 13:54 ` Christian König
2021-03-25 13:56 ` Jason Gunthorpe
2021-03-25 7:49 ` Christian König
2021-03-25 9:41 ` Daniel Vetter
2021-03-23 13:52 ` Jason Gunthorpe
2021-03-23 15:05 ` Thomas Hellström (Intel)
2021-03-23 19:52 ` Williams, Dan J
2021-03-23 20:42 ` Thomas Hellström (Intel)
2021-03-24 9:58 ` Daniel Vetter
2021-03-24 10:05 ` Thomas Hellström (Intel)
2021-03-24 16:34 ` Dave Hansen
2021-03-24 20:22 ` Thomas Hellström (Intel)
2021-03-24 20:25 ` Dave Hansen
2021-03-25 17:51 ` Thomas Hellström (Intel)
2021-03-25 17:55 ` Jason Gunthorpe
2021-03-25 18:13 ` Thomas Hellström (Intel)
2021-03-25 18:24 ` Jason Gunthorpe
2021-03-25 18:42 ` Thomas Hellström (Intel)
2021-03-26 9:08 ` Thomas Hellström (Intel)
2021-03-26 11:46 ` Jason Gunthorpe
2021-03-26 12:33 ` Thomas Hellström (Intel)
2021-03-21 18:45 ` [RFC PATCH 2/2] mm,drm/ttm: Use VM_PFNMAP for TTM vmas Thomas Hellström (Intel)
2021-03-22 7:47 ` Christian König
2021-03-22 8:13 ` Thomas Hellström (Intel)
2021-03-23 11:57 ` Christian König
2021-03-23 11:47 ` Daniel Vetter
2021-03-23 14:04 ` Jason Gunthorpe
2021-03-23 15:51 ` Thomas Hellström (Intel)
2021-03-23 14:00 ` Jason Gunthorpe
2021-03-23 15:46 ` Thomas Hellström (Intel)
2021-03-23 16:06 ` Jason Gunthorpe
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