From: Jason Gunthorpe <jgg@ziepe.ca>
To: Leon Romanovsky <leon@kernel.org>
Cc: "Yonatan Maman" <ymaman@nvidia.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Lyude Paul" <lyude@redhat.com>,
"Danilo Krummrich" <dakr@kernel.org>,
"David Airlie" <airlied@gmail.com>,
"Simona Vetter" <simona@ffwll.ch>,
"Alistair Popple" <apopple@nvidia.com>,
"Ben Skeggs" <bskeggs@nvidia.com>,
"Michael Guralnik" <michaelgur@nvidia.com>,
"Or Har-Toov" <ohartoov@nvidia.com>,
"Daisuke Matsuda" <dskmtsd@gmail.com>,
"Shay Drory" <shayd@nvidia.com>,
linux-mm@kvack.org, linux-rdma@vger.kernel.org,
dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 0/5] *** GPU Direct RDMA (P2P DMA) for Device Private Pages ***
Date: Wed, 23 Jul 2025 01:03:47 -0300 [thread overview]
Message-ID: <aIBfIxVBR/3ig/O/@ziepe.ca> (raw)
In-Reply-To: <20250721064904.GK402218@unreal>
On Mon, Jul 21, 2025 at 09:49:04AM +0300, Leon Romanovsky wrote:
> > In fact, hmm_range_fault doesn't have information about the destination
> > device that will perform the DMA mapping.
>
> So probably you need to teach HMM to perform page_faults on specific device.
That isn't how the HMM side is supposed to work, this API is just
giving the one and only P2P page that is backing the device private.
The providing driver shouldn't be doing any p2pdma operations to check
feasibility.
Otherwise we are doing p2p operations twice on every page, doesn't
make sense.
We've consistently been saying the P2P is done during the DMA mapping
side only, I think we should stick with that. Failing P2P is an
exception case, and the fix is to trigger page migration which the
general hmm code knows how to do. So calling hmm range fault again
makes sense to me. I wouldn't want drivers open coding the migration
logic in the new callback.
Jason
next prev parent reply other threads:[~2025-07-23 4:03 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-18 11:51 [PATCH v2 0/5] *** GPU Direct RDMA (P2P DMA) for Device Private Pages *** Yonatan Maman
2025-07-18 11:51 ` [PATCH v2 1/5] mm/hmm: HMM API to enable P2P DMA for device private pages Yonatan Maman
2025-07-18 14:17 ` Matthew Wilcox
2025-07-18 14:44 ` Jason Gunthorpe
2025-07-21 0:11 ` Alistair Popple
2025-07-21 13:23 ` Matthew Wilcox
2025-07-22 0:49 ` Alistair Popple
2025-07-23 3:51 ` Jason Gunthorpe
2025-07-23 4:10 ` Alistair Popple
2025-07-24 8:52 ` David Hildenbrand
2025-07-25 0:31 ` Alistair Popple
2025-07-25 9:51 ` David Hildenbrand
2025-08-01 16:40 ` Jason Gunthorpe
2025-08-01 16:50 ` David Hildenbrand
2025-08-01 16:57 ` Jason Gunthorpe
2025-08-04 1:51 ` Alistair Popple
2025-08-05 14:09 ` Jason Gunthorpe
2025-08-04 7:48 ` David Hildenbrand
2025-07-21 6:59 ` Christoph Hellwig
2025-07-22 5:42 ` Yonatan Maman
2025-08-01 16:52 ` Jason Gunthorpe
2025-07-18 11:51 ` [PATCH v2 2/5] nouveau/dmem: HMM P2P DMA for private dev pages Yonatan Maman
2025-07-21 7:00 ` Christoph Hellwig
2025-07-22 5:23 ` Yonatan Maman
2025-07-18 11:51 ` [PATCH v2 3/5] IB/core: P2P DMA for device private pages Yonatan Maman
2025-07-18 11:51 ` [PATCH v2 4/5] RDMA/mlx5: Enable P2P DMA with fallback mechanism Yonatan Maman
2025-07-21 7:03 ` Christoph Hellwig
2025-07-23 3:55 ` Jason Gunthorpe
2025-07-24 7:30 ` Christoph Hellwig
2025-08-01 16:46 ` Jason Gunthorpe
2025-07-18 11:51 ` [PATCH v2 5/5] RDMA/mlx5: Enabling ATS for ODP memory Yonatan Maman
2025-07-20 10:30 ` [PATCH v2 0/5] *** GPU Direct RDMA (P2P DMA) for Device Private Pages *** Leon Romanovsky
2025-07-20 21:03 ` Yonatan Maman
2025-07-21 6:49 ` Leon Romanovsky
2025-07-23 4:03 ` Jason Gunthorpe [this message]
2025-07-23 8:44 ` Leon Romanovsky
2025-07-21 6:54 ` Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=aIBfIxVBR/3ig/O/@ziepe.ca \
--to=jgg@ziepe.ca \
--cc=airlied@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=apopple@nvidia.com \
--cc=bskeggs@nvidia.com \
--cc=dakr@kernel.org \
--cc=dri-devel@lists.freedesktop.org \
--cc=dskmtsd@gmail.com \
--cc=jglisse@redhat.com \
--cc=leon@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-rdma@vger.kernel.org \
--cc=lyude@redhat.com \
--cc=michaelgur@nvidia.com \
--cc=nouveau@lists.freedesktop.org \
--cc=ohartoov@nvidia.com \
--cc=shayd@nvidia.com \
--cc=simona@ffwll.ch \
--cc=ymaman@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).