From: Jason Gunthorpe <jgg@mellanox.com>
To: "Kuehling, Felix" <Felix.Kuehling@amd.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
Jerome Glisse <jglisse@redhat.com>,
Ralph Campbell <rcampbell@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
"linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
"Deucher, Alexander" <Alexander.Deucher@amd.com>,
Ben Skeggs <bskeggs@redhat.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
"Koenig, Christian" <Christian.Koenig@amd.com>,
"Zhou, David(ChunMing)" <David1.Zhou@amd.com>,
Dennis Dalessandro <dennis.dalessandro@intel.com>,
Juergen Gross <jgross@suse.com>,
Mike Marciniszyn <mike.marciniszyn@intel.com>,
Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>,
Petr Cvek <petrcvekcz@gmail.com>,
Stefano Stabellini <sstabellini@kernel.org>,
"nouveau@lists.freedesktop.org" <nouveau@lists.freedesktop.org>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v2 12/15] drm/amdgpu: Call find_vma under mmap_sem
Date: Tue, 29 Oct 2019 17:19:12 +0000 [thread overview]
Message-ID: <20191029171908.GP22766@mellanox.com> (raw)
In-Reply-To: <a368d1bf-ba69-bb63-2bfd-b674acc2f19b@amd.com>
On Tue, Oct 29, 2019 at 04:28:43PM +0000, Kuehling, Felix wrote:
> On 2019-10-28 4:10 p.m., Jason Gunthorpe wrote:
> > From: Jason Gunthorpe <jgg@mellanox.com>
> >
> > find_vma() must be called under the mmap_sem, reorganize this code to
> > do the vma check after entering the lock.
> >
> > Further, fix the unlocked use of struct task_struct's mm, instead use
> > the mm from hmm_mirror which has an active mm_grab. Also the mm_grab
> > must be converted to a mm_get before acquiring mmap_sem or calling
> > find_vma().
> >
> > Fixes: 66c45500bfdc ("drm/amdgpu: use new HMM APIs and helpers")
> > Fixes: 0919195f2b0d ("drm/amdgpu: Enable amdgpu_ttm_tt_get_user_pages in worker threads")
> > Cc: Alex Deucher <alexander.deucher@amd.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Cc: David (ChunMing) Zhou <David1.Zhou@amd.com>
> > Cc: amd-gfx@lists.freedesktop.org
> > Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
>
> One question inline to confirm my understanding. Otherwise this patch is
>
> Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Thanks
> > - if (unlikely((gtt->userflags & AMDGPU_GEM_USERPTR_ANONONLY) &&
> > - vma->vm_file)) {
> > - r = -EPERM;
> > - goto out;
> > - }
> > + mm = mirror->hmm->mmu_notifier.mm;
> > + if (!mmget_not_zero(mm)) /* Happens during process shutdown */
>
> This works because mirror->hmm->mmu_notifier holds an mmgrab reference
> to the mm?
Yes, this makes sure the mm pointer remains valid
> So the MM will not just go away, but if the mmget refcount is 0, it
> means the mm is marked for destruction and shouldn't be used any
> more.
Not just marked for destruction, but that another thread is
progressing or finished release().
The other detail here is that in general you can't get the mmap_sem
without also having a mmget as exit_mmap() does not lock the mmap_sem
in some places where it alters the datastructures. ie racing
find_vma() with exit_mmap() is not allowed.
This means we have to hold the mmget across the hmm_range_fault(), but
we can drop the mmget and then test mmu_range_read_retry() under the
driver lock. It will return true if the mmget refcount has gone to
zero in the mean time.
But I think this is probably a poor driver design, a driver should
just hold the mmget() until it has completed establishing the shadow
PTEs, as it is hard to see a reason not to..
Jason
next prev parent reply other threads:[~2019-10-29 17:19 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-28 20:10 [PATCH v2 00/15] Consolidate the mmu notifier interval_tree and locking Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 01/15] mm/mmu_notifier: define the header pre-processor parts even if disabled Jason Gunthorpe
2019-11-05 21:23 ` John Hubbard
2019-11-06 13:36 ` Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier Jason Gunthorpe
2019-10-29 22:04 ` Kuehling, Felix
2019-10-29 22:56 ` Jason Gunthorpe
2019-11-07 0:23 ` John Hubbard
2019-11-07 2:08 ` Jerome Glisse
2019-11-07 20:11 ` Jason Gunthorpe
2019-11-07 21:04 ` Jerome Glisse
2019-11-08 0:32 ` Jason Gunthorpe
2019-11-08 2:00 ` Jerome Glisse
2019-11-08 20:19 ` Jason Gunthorpe
2019-11-07 20:06 ` Jason Gunthorpe
2019-11-07 20:53 ` John Hubbard
2019-11-08 15:26 ` Jason Gunthorpe
2019-11-08 6:33 ` Christoph Hellwig
2019-11-08 13:43 ` Jerome Glisse
2019-10-28 20:10 ` [PATCH v2 03/15] mm/hmm: allow hmm_range to be used with a mmu_range_notifier or hmm_mirror Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 04/15] mm/hmm: define the pre-processor related parts of hmm.h even if disabled Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 05/15] RDMA/odp: Use mmu_range_notifier_insert() Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 06/15] RDMA/hfi1: Use mmu_range_notifier_inset for user_exp_rcv Jason Gunthorpe
2019-10-29 12:19 ` Dennis Dalessandro
2019-10-29 12:51 ` Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 07/15] drm/radeon: use mmu_range_notifier_insert Jason Gunthorpe
2019-10-29 7:48 ` Koenig, Christian
2019-10-28 20:10 ` [PATCH v2 08/15] xen/gntdev: Use select for DMA_SHARED_BUFFER Jason Gunthorpe
2019-11-01 18:26 ` Jason Gunthorpe
2019-11-05 14:44 ` Jürgen Groß
2019-11-07 9:39 ` Jürgen Groß
2019-10-28 20:10 ` [PATCH v2 09/15] xen/gntdev: use mmu_range_notifier_insert Jason Gunthorpe
2019-10-30 16:55 ` Boris Ostrovsky
2019-11-01 17:48 ` Jason Gunthorpe
2019-11-01 18:51 ` Boris Ostrovsky
2019-11-01 19:17 ` Jason Gunthorpe
2019-11-04 22:03 ` Boris Ostrovsky
2019-11-05 2:31 ` Jason Gunthorpe
2019-11-05 15:16 ` Boris Ostrovsky
2019-11-07 20:36 ` Jason Gunthorpe
2019-11-07 22:54 ` Boris Ostrovsky
2019-11-08 14:53 ` Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 10/15] nouveau: use mmu_notifier directly for invalidate_range_start Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 11/15] nouveau: use mmu_range_notifier instead of hmm_mirror Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 13/15] drm/amdgpu: Use mmu_range_insert " Jason Gunthorpe
2019-10-29 7:51 ` Koenig, Christian
2019-10-29 13:59 ` Jason Gunthorpe
2019-10-29 22:14 ` Kuehling, Felix
2019-10-29 23:09 ` Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 14/15] drm/amdgpu: Use mmu_range_notifier " Jason Gunthorpe
2019-10-29 19:22 ` Yang, Philip
2019-10-29 19:25 ` Jason Gunthorpe
2019-11-01 14:44 ` Yang, Philip
2019-11-01 15:12 ` Jason Gunthorpe
2019-11-01 15:59 ` Yang, Philip
2019-11-01 17:42 ` Jason Gunthorpe
2019-11-01 19:19 ` Jason Gunthorpe
2019-11-01 19:45 ` Yang, Philip
2019-11-01 19:50 ` Yang, Philip
2019-11-01 19:51 ` Jason Gunthorpe
2019-11-01 18:21 ` Jason Gunthorpe
2019-11-01 18:34 ` [PATCH v2a " Jason Gunthorpe
2019-10-28 20:10 ` [PATCH v2 15/15] mm/hmm: remove hmm_mirror and related Jason Gunthorpe
[not found] ` <20191028201032.6352-13-jgg@ziepe.ca>
2019-10-29 7:49 ` [PATCH v2 12/15] drm/amdgpu: Call find_vma under mmap_sem Koenig, Christian
2019-10-29 16:28 ` Kuehling, Felix
2019-10-29 13:07 ` Christian König
2019-10-29 17:19 ` Jason Gunthorpe [this message]
2019-11-01 19:54 ` [PATCH v2 00/15] Consolidate the mmu notifier interval_tree and locking Jason Gunthorpe
2019-11-01 20:54 ` Ralph Campbell
2019-11-04 20:40 ` Jason Gunthorpe
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=20191029171908.GP22766@mellanox.com \
--to=jgg@mellanox.com \
--cc=Alexander.Deucher@amd.com \
--cc=Christian.Koenig@amd.com \
--cc=David1.Zhou@amd.com \
--cc=Felix.Kuehling@amd.com \
--cc=amd-gfx@lists.freedesktop.org \
--cc=boris.ostrovsky@oracle.com \
--cc=bskeggs@redhat.com \
--cc=dennis.dalessandro@intel.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hch@infradead.org \
--cc=jglisse@redhat.com \
--cc=jgross@suse.com \
--cc=jhubbard@nvidia.com \
--cc=linux-mm@kvack.org \
--cc=linux-rdma@vger.kernel.org \
--cc=mike.marciniszyn@intel.com \
--cc=nouveau@lists.freedesktop.org \
--cc=oleksandr_andrushchenko@epam.com \
--cc=petrcvekcz@gmail.com \
--cc=rcampbell@nvidia.com \
--cc=sstabellini@kernel.org \
--cc=xen-devel@lists.xenproject.org \
/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).