From: Alistair Popple <apopple@nvidia.com>
To: Alex Sierra <alex.sierra@amd.com>,
Joao Martins <joao.m.martins@oracle.com>
Cc: <amd-gfx@lists.freedesktop.org>,
<dri-devel@lists.freedesktop.org>, <hch@lst.de>,
<jglisse@redhat.com>, <willy@infradead.org>,
<akpm@linux-foundation.org>, <Felix.Kuehling@amd.com>,
<linux-mm@kvack.org>, <rcampbell@nvidia.com>,
<linux-ext4@vger.kernel.org>, <linux-xfs@vger.kernel.org>,
<jgg@nvidia.com>
Subject: Re: [PATCH v3 03/10] mm/gup: fail get_user_pages for LONGTERM dev coherent type
Date: Fri, 21 Jan 2022 00:18:15 +1100 [thread overview]
Message-ID: <2432841.uOC12ROH9Y@nvdebian> (raw)
In-Reply-To: <008b5ff4-dd53-d652-46dd-5ce771c69a0a@oracle.com>
On Thursday, 20 January 2022 11:36:21 PM AEDT Joao Martins wrote:
> On 1/10/22 22:31, Alex Sierra wrote:
> > Avoid long term pinning for Coherent device type pages. This could
> > interfere with their own device memory manager. For now, we are just
> > returning error for PIN_LONGTERM Coherent device type pages. Eventually,
> > these type of pages will get migrated to system memory, once the device
> > migration pages support is added.
> >
> > Signed-off-by: Alex Sierra <alex.sierra@amd.com>
> > ---
> > mm/gup.c | 7 +++++++
> > 1 file changed, 7 insertions(+)
> >
> > diff --git a/mm/gup.c b/mm/gup.c
> > index 886d6148d3d0..9c8a075d862d 100644
> > --- a/mm/gup.c
> > +++ b/mm/gup.c
> > @@ -1720,6 +1720,12 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
> > * If we get a movable page, since we are going to be pinning
> > * these entries, try to move them out if possible.
> > */
> > + if (is_device_page(head)) {
> > + WARN_ON_ONCE(is_device_private_page(head));
> > + ret = -EFAULT;
> > + goto unpin_pages;
> > + }
> > +
>
> Wouldn't be more efficient for you failing earlier instead of after all the pages are pinned?
Rather than failing I think the plan is to migrate the device coherent pages
like we do for ZONE_MOVABLE, so leaving this here is a good place holder until
that is done. Currently we are missing some functionality required to do that
but I am hoping to post a series fixing that soon.
> Filesystem DAX suffers from a somewhat similar issue[0] -- albeit it's more related to
> blocking FOLL_LONGTERM in gup-fast while gup-slow can still do it. Coherent devmap appears
> to want to block it in all gup.
>
> On another thread Jason was suggesting about having different pgmap::flags to capture
> these special cases[1] instead of selecting what different pgmap types can do in various
> different places.
>
> [0] https://lore.kernel.org/linux-mm/6a18179e-65f7-367d-89a9-d5162f10fef0@oracle.com/
> [1] https://lore.kernel.org/linux-mm/20211019160136.GH3686969@ziepe.ca/
>
next prev parent reply other threads:[~2022-01-20 13:18 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-10 22:31 [PATCH v3 00/10] Add MEMORY_DEVICE_COHERENT for coherent device memory mapping Alex Sierra
2022-01-10 22:31 ` [PATCH v3 01/10] mm: add zone device coherent type memory support Alex Sierra
2022-01-20 4:08 ` Alistair Popple
2022-01-10 22:31 ` [PATCH v3 02/10] mm: add device coherent vma selection for memory migration Alex Sierra
2022-01-10 22:31 ` [PATCH v3 03/10] mm/gup: fail get_user_pages for LONGTERM dev coherent type Alex Sierra
2022-01-20 12:36 ` Joao Martins
2022-01-20 13:18 ` Alistair Popple [this message]
2022-01-10 22:31 ` [PATCH v3 04/10] drm/amdkfd: add SPM support for SVM Alex Sierra
2022-01-10 22:31 ` [PATCH v3 05/10] drm/amdkfd: coherent type as sys mem on migration to ram Alex Sierra
2022-01-10 22:31 ` [PATCH v3 06/10] lib: test_hmm add ioctl to get zone device type Alex Sierra
2022-01-20 5:01 ` Alistair Popple
2022-01-10 22:31 ` [PATCH v3 07/10] lib: test_hmm add module param for " Alex Sierra
2022-01-20 5:23 ` Alistair Popple
2022-01-10 22:31 ` [PATCH v3 08/10] lib: add support for device coherent type in test_hmm Alex Sierra
2022-01-20 6:00 ` Alistair Popple
2022-01-10 22:32 ` [PATCH v3 09/10] tools: update hmm-test to support device coherent type Alex Sierra
2022-01-20 6:14 ` Alistair Popple
2022-01-27 3:22 ` Sierra Guiza, Alejandro (Alex)
2022-01-10 22:32 ` [PATCH v3 10/10] tools: update test_hmm script to support SP config Alex Sierra
2022-01-20 6:17 ` Alistair Popple
2022-01-12 11:06 ` [PATCH v3 00/10] Add MEMORY_DEVICE_COHERENT for coherent device memory mapping Alistair Popple
2022-01-20 6:33 ` Alistair Popple
2022-01-12 11:16 ` David Hildenbrand
2022-01-12 16:08 ` Felix Kuehling
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