From: David Hildenbrand <david@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
John Hubbard <jhubbard@nvidia.com>,
nouveau@lists.freedesktop.org,
Alistair Popple <apopple@nvidia.com>,
DRI Development <dri-devel@lists.freedesktop.org>,
Karol Herbst <kherbst@redhat.com>, Lyude Paul <lyude@redhat.com>,
Danilo Krummrich <dakr@kernel.org>
Subject: Re: [Question] Are "device exclusive non-swap entries" / "SVM atomics in Nouveau" still getting used in practice?
Date: Fri, 24 Jan 2025 15:39:18 +0100 [thread overview]
Message-ID: <d4e234c1-d200-42ec-8667-031f6e4953f1@redhat.com> (raw)
In-Reply-To: <20250124141121.GY5556@nvidia.com>
On 24.01.25 15:11, Jason Gunthorpe wrote:
> On Fri, Jan 24, 2025 at 11:44:28AM +0100, David Hildenbrand wrote:
>
>> There are other concerns I have (what if the page is pinned and access
>> outside of the user space page tables?). Maybe there was not need to handle
>> these cases so far.
>
> I think alot of this depends on userspace following some restrictions
> so that the pages are always convertible. Presumably if the userspace
> breaks things then their atomic using GPU kernels will fault.
>
> So, from a kernel perspective, I'd suggest that creating a reasonable
> set of conditions that userspace can follow to have it work reliably
> is a reasonable goal.
Yes, that's my assumption as well. If you register a page using io_uring
as a fixed buffer and then trigger "device_exclusive" access, the page
can still be read/written using io_uring and atomics might not work as
expected. "Not supported".
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2025-01-24 14:39 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-23 10:20 David Hildenbrand
2025-01-23 15:08 ` Simona Vetter
2025-01-24 10:44 ` David Hildenbrand
2025-01-24 14:11 ` Jason Gunthorpe
2025-01-24 14:39 ` David Hildenbrand [this message]
2025-01-24 15:28 ` Simona Vetter
2025-01-24 17:54 ` David Hildenbrand
2025-01-28 0:09 ` Alistair Popple
2025-01-28 20:14 ` Simona Vetter
2025-01-28 20:24 ` David Hildenbrand
2025-01-29 10:48 ` Simona Vetter
2025-01-29 11:28 ` Simona Vetter
2025-01-29 11:31 ` David Hildenbrand
2025-01-29 14:05 ` Simona Vetter
2025-01-29 16:13 ` David Hildenbrand
2025-01-30 8:55 ` Simona Vetter
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