From: Daniel Vetter <daniel@ffwll.ch>
To: "Thomas Hellström (Intel)" <thomas_os@shipmail.org>
Cc: "DRI Development" <dri-devel@lists.freedesktop.org>,
"Christian König" <christian.koenig@amd.com>,
"Jason Gunthorpe" <jgg@nvidia.com>
Subject: Re: Fence wait in mmu_interval_notifier_ops::invalidate
Date: Mon, 14 Dec 2020 10:52:37 +0100 [thread overview]
Message-ID: <20201214095237.GX401619@phenom.ffwll.local> (raw)
In-Reply-To: <ae0e1e69-6550-94fb-c2b2-1ea04a0ae936@shipmail.org>
On Sun, Dec 13, 2020 at 04:09:25PM +0100, Thomas Hellström (Intel) wrote:
>
> On 12/11/20 1:46 PM, Jason Gunthorpe wrote:
> > On Fri, Dec 11, 2020 at 08:50:53AM +0100, Thomas Hellström (Intel) wrote:
> >
> > > My understanding of this particular case is that hardware would continue to
> > > DMA to orphaned pages that are pinned until the driver is done with
> > > DMA,
> > mmu notifier replaces pinning as the locking mechanism. Drivers using
> > mmu notifier should not be taking pins.
> >
> > Keep in mind this was all built for HW with real shadow page tables
> > that can do fine grained manipulation.
> OK yes, that makes sense and in that context the fence wait is easier to
> understand. Looks like for example the radeon driver is using the notifier +
> get_user_pages() but there it looks like it's used to avoid having
> get_user_pages() clash with invalidation.
I think the radeon userptr implementation is bad enough that Christian
wants to outright remove it. At least he keeps talking about doing that.
So maybe not a good example to look at :-)
-Daniel
> > The GPU version of this to instead manipulate a command queue is a big
> > aberration from what was intended.
> >
> > Jason
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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next prev parent reply other threads:[~2020-12-14 9:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-09 16:36 Fence wait in mmu_interval_notifier_ops::invalidate Thomas Hellström (Intel)
2020-12-09 16:37 ` Jason Gunthorpe
2020-12-09 16:46 ` Thomas Hellström (Intel)
2020-12-10 10:53 ` Christian König
2020-12-11 7:50 ` Thomas Hellström (Intel)
2020-12-11 8:57 ` Christian König
2020-12-11 9:37 ` Thomas Hellström (Intel)
2020-12-11 12:46 ` Jason Gunthorpe
2020-12-13 15:09 ` Thomas Hellström (Intel)
2020-12-14 9:52 ` Daniel Vetter [this message]
2020-12-14 10:21 ` Christian König
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