From: Peter Xu <peterx@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>,
linux-mm@kvack.org, nouveau@lists.freedesktop.org,
bskeggs@redhat.com, akpm@linux-foundation.org,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, jhubbard@nvidia.com,
rcampbell@nvidia.com, jglisse@redhat.com, hch@infradead.org,
daniel@ffwll.ch, willy@infradead.org, bsingharora@gmail.com,
Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v8 5/8] mm: Device exclusive memory access
Date: Tue, 18 May 2021 19:45:05 -0400 [thread overview]
Message-ID: <YKRRgZmRMdk1vH7A@t490s> (raw)
In-Reply-To: <20210518230327.GG1002214@nvidia.com>
On Tue, May 18, 2021 at 08:03:27PM -0300, Jason Gunthorpe wrote:
> Logically during fork all these device exclusive pages should be
> reverted back to their CPU pages, write protected and the CPU page PTE
> copied to the fork.
>
> We should not copy the device exclusive page PTE to the fork. I think
> I pointed to this on an earlier rev..
Agreed. Though please see the question I posted in the other thread: now I am
not very sure whether we'll be able to mark a page as device exclusive if that
page has mapcount>1.
>
> We can optimize this into the various variants above, but logically
> device exclusive stop existing during fork.
Makes sense, I think that's indeed what this patch did at least for the COW
case, so I think Alistair did address that comment. It's just that I think we
need to drop the other !COW case (imho that should correspond to the changes in
copy_nonpresent_pte()) in this patch to guarantee it.
I also hope we don't make copy_pte_range() even more complicated just to do the
lock_page() right, so we could fail the fork() if the lock is hard to take.
--
Peter Xu
next prev parent reply other threads:[~2021-05-18 23:45 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 8:42 [PATCH v8 0/8] Add support for SVM atomics in Nouveau Alistair Popple
2021-04-07 8:42 ` [PATCH v8 1/8] mm: Remove special swap entry functions Alistair Popple
2021-05-18 2:17 ` Peter Xu
2021-05-18 11:58 ` Alistair Popple
2021-05-18 14:17 ` Peter Xu
2021-04-07 8:42 ` [PATCH v8 2/8] mm/swapops: Rework swap entry manipulation code Alistair Popple
2021-04-07 8:42 ` [PATCH v8 3/8] mm/rmap: Split try_to_munlock from try_to_unmap Alistair Popple
2021-05-18 20:04 ` Liam Howlett
2021-05-19 12:38 ` Alistair Popple
2021-05-20 20:24 ` Liam Howlett
2021-05-21 2:23 ` Alistair Popple
2021-04-07 8:42 ` [PATCH v8 4/8] mm/rmap: Split migration into its own function Alistair Popple
2021-04-07 8:42 ` [PATCH v8 5/8] mm: Device exclusive memory access Alistair Popple
2021-05-18 2:08 ` Peter Xu
2021-05-18 13:19 ` Alistair Popple
2021-05-18 17:27 ` Peter Xu
2021-05-18 17:33 ` Jason Gunthorpe
2021-05-18 18:01 ` Peter Xu
2021-05-18 19:45 ` Jason Gunthorpe
2021-05-18 20:29 ` Peter Xu
2021-05-18 23:03 ` Jason Gunthorpe
2021-05-18 23:45 ` Peter Xu [this message]
2021-05-19 11:04 ` Alistair Popple
2021-05-19 12:15 ` Peter Xu
2021-05-19 13:11 ` Alistair Popple
2021-05-19 14:04 ` Peter Xu
2021-05-19 13:28 ` Jason Gunthorpe
2021-05-19 14:09 ` Peter Xu
2021-05-19 18:11 ` Jason Gunthorpe
2021-05-19 11:35 ` Alistair Popple
2021-05-19 12:21 ` Peter Xu
2021-05-19 12:46 ` Alistair Popple
2021-05-21 6:53 ` Alistair Popple
2021-05-18 21:16 ` Peter Xu
2021-05-19 10:49 ` Alistair Popple
2021-05-19 12:24 ` Peter Xu
2021-05-19 12:46 ` Alistair Popple
2021-04-07 8:42 ` [PATCH v8 6/8] mm: Selftests for exclusive device memory Alistair Popple
2021-04-07 8:42 ` [PATCH v8 7/8] nouveau/svm: Refactor nouveau_range_fault Alistair Popple
2021-04-07 8:42 ` [PATCH v8 8/8] nouveau/svm: Implement atomic SVM access Alistair Popple
2021-05-21 4:04 ` Ben Skeggs
2021-05-06 7:43 ` [PATCH v8 0/8] Add support for SVM atomics in Nouveau Alistair Popple
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