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From: Oded Gabbay <ogabbay@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David Hildenbrand <david@redhat.com>,
	Jason Gunthorpe <jgg@ziepe.ca>, Jan Kara <jack@suse.cz>,
	John Hubbard <jhubbard@nvidia.com>,
	Leon Romanovsky <leonro@nvidia.com>,
	Linux-MM <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"Maya B . Gokhale" <gokhale2@llnl.gov>,
	Yang Shi <yang.shi@linux.alibaba.com>,
	Marty Mcfadden <mcfadden8@llnl.gov>,
	Kirill Shutemov <kirill@shutemov.name>,
	Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
	Kirill Tkhai <ktkhai@virtuozzo.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Christoph Hellwig <hch@lst.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Peter Xu <peterx@redhat.com>,
	dave@sr71.net
Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification
Date: Wed, 16 Feb 2022 21:20:49 +0200	[thread overview]
Message-ID: <CAFCwf10WEwrZzD7nWkyaZYnnYtZs0aWYwBniEPrb_xdgiQiggw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wgLk5xWj8v6mQXaWL0zWAf2cis8EpPkQUuEZ7K3LxVQHQ@mail.gmail.com>

On Wed, Feb 16, 2022 at 9:04 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> [ Added David Hildenbrand to the participants. David, see
>
>     https://bugzilla.kernel.org/show_bug.cgi?id=215616
>
>   for details ]
>
> On Wed, Feb 16, 2022 at 8:59 AM Oded Gabbay <oded.gabbay@gmail.com> wrote:
> >
> > All the details are in the bug, but the bottom line is that somehow,
> > this patch causes corruption when the numa balancing feature is
> > enabled AND we don't use process affinity AND we use GUP to pin pages
> > so our accelerator can DMA to/from system memory.
>
> Hmm. I thought all the remaining issues were related to THP - and
> David Hildenbrand had a series to fix those up.
>
> The fact that it also shows up with numa balancing is a bit
> unfortunate, because I think that means that that patch series may not
> have caught that case.
>
> That said - what does "we use GUP to pin pages" mean? Does it actually
> use the pinning logic, or just regular old GUP?
>
> I'm assuming this is just the existing pin_user_pages_fast() (ie a
> proper pin) in drivers/misc/habanalabs/common/memory.c. But I wanted
> to confirm that it's not some other situation.
>
>                    Linus
>
[Adding dave hansen as we chatted about it in irc]

It uses the pinning logic, simply calling pin_user_pages_fast with the
relevant gup flags to pin the userspace memory so we can after that
dma map it and give the bus address to the h/w.

And afaik, the gup flags combination we use
(FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM) is the correct combination,
at least according to the last time it was discussed with Daniel,
Jason and other people.

Oded

  reply	other threads:[~2022-02-16 19:21 UTC|newest]

Thread overview: 98+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21 23:49 [PATCH 0/4] mm: Simplfy cow handling Peter Xu
2020-08-21 23:49 ` [PATCH 1/4] mm: Trial do_wp_page() simplification Peter Xu
2020-08-24  8:36   ` Kirill Tkhai
2020-08-24 14:30     ` Jan Kara
2020-08-24 15:37       ` Kirill Tkhai
2020-08-24 18:22         ` Linus Torvalds
2020-09-01  7:01           ` Hugh Dickins
2020-09-14 14:38   ` Jason Gunthorpe
2020-09-14 17:32     ` Linus Torvalds
2020-09-14 18:34       ` Peter Xu
2020-09-14 21:15         ` Peter Xu
2020-09-14 22:55           ` Jason Gunthorpe
2020-09-14 22:59             ` Linus Torvalds
2020-09-14 23:28               ` Jason Gunthorpe
2020-09-15  0:19                 ` Linus Torvalds
2020-09-15 14:50                 ` Peter Xu
2020-09-15 15:17                   ` Peter Xu
2020-09-15 16:05                   ` Jason Gunthorpe
2020-09-15 18:29                     ` Jason Gunthorpe
2020-09-15 19:13                       ` Peter Xu
2020-09-15 19:38                         ` Jason Gunthorpe
2020-09-15 21:33                           ` Peter Xu
2020-09-15 23:22                             ` Jason Gunthorpe
2020-09-16  1:50                               ` John Hubbard
2020-09-16 17:48                                 ` Jason Gunthorpe
2020-09-16 18:46                                   ` Peter Xu
2020-09-17 11:25                                     ` Jason Gunthorpe
2020-09-17 18:11                                       ` Linus Torvalds
2020-09-17 19:38                                         ` Jason Gunthorpe
2020-09-17 19:51                                           ` Linus Torvalds
2020-09-18 16:40                                             ` Peter Xu
2020-09-18 17:16                                               ` Linus Torvalds
2020-09-18 19:57                                                 ` Peter Xu
2020-09-18 17:32                                               ` Jason Gunthorpe
2020-09-18 20:40                                                 ` Peter Xu
2020-09-18 20:59                                                   ` Linus Torvalds
2020-09-19  0:28                                                     ` Jason Gunthorpe
2020-09-18 21:06                                                   ` John Hubbard
2020-09-19  0:01                                                     ` Jason Gunthorpe
2020-09-21  8:35                                                       ` Jan Kara
2020-09-21 12:03                                                         ` Jason Gunthorpe
2022-02-16 16:59                                                           ` Oded Gabbay
2022-02-16 17:24                                                             ` Oded Gabbay
2022-02-16 19:04                                                             ` Linus Torvalds
2022-02-16 19:20                                                               ` Oded Gabbay [this message]
2022-02-16 19:24                                                               ` David Hildenbrand
2020-09-21 13:42                                               ` Michal Hocko
2020-09-21 14:18                                                 ` Peter Xu
2020-09-21 14:28                                                   ` Michal Hocko
2020-09-21 14:38                                                     ` Tejun Heo
2020-09-21 14:43                                                       ` Christian Brauner
2020-09-21 14:55                                                         ` Michal Hocko
2020-09-21 15:04                                                           ` Christian Brauner
2020-09-21 16:06                                                             ` Michal Hocko
2020-09-23  7:53                                                               ` Michal Hocko
2020-09-21 14:41                                                 ` Christian Brauner
2020-09-21 14:57                                                   ` Michal Hocko
2020-09-21 16:31                                                     ` Peter Xu
2020-09-17 18:14                                       ` Peter Xu
2020-09-17 18:26                                         ` Linus Torvalds
2020-09-17 19:03                                           ` Peter Xu
2020-09-17 19:42                                             ` Linus Torvalds
2020-09-17 19:55                                               ` John Hubbard
2020-09-17 20:06                                               ` Jason Gunthorpe
2020-09-17 20:19                                                 ` John Hubbard
2020-09-17 20:25                                                   ` Jason Gunthorpe
2020-09-17 20:35                                                 ` Linus Torvalds
2020-09-17 21:40                                                   ` Peter Xu
2020-09-17 22:09                                                     ` Jason Gunthorpe
2020-09-17 22:25                                                       ` Linus Torvalds
2020-09-17 22:48                                                       ` Ira Weiny
2020-09-18  9:36                                                         ` Jan Kara
2020-09-18  9:44                                                       ` Jan Kara
2020-09-18 16:19                                             ` Jason Gunthorpe
2020-09-15 10:23           ` Leon Romanovsky
2020-09-15 15:56           ` Jason Gunthorpe
2020-09-15 15:03   ` Oleg Nesterov
2020-09-15 16:18     ` Peter Xu
2020-08-21 23:49 ` [PATCH 2/4] mm/ksm: Remove reuse_ksm_page() Peter Xu
2020-08-21 23:49 ` [PATCH 3/4] mm/gup: Remove enfornced COW mechanism Peter Xu
2020-09-14 14:27   ` Oleg Nesterov
2020-09-14 17:59     ` Peter Xu
2020-09-14 19:03       ` Linus Torvalds
2020-08-21 23:49 ` [PATCH 4/4] mm: Add PGREUSE counter Peter Xu
2020-08-22 16:14   ` Linus Torvalds
2020-08-24  0:24     ` Peter Xu
2020-08-22 16:05 ` [PATCH 0/4] mm: Simplfy cow handling Linus Torvalds
2020-08-23 23:58   ` Peter Xu
2020-08-24  8:38 ` Kirill Tkhai
2020-08-27 14:15 ` Peter Xu
2021-02-02 14:40 [PATCH 1/4] mm: Trial do_wp_page() simplification Gal Pressman
2021-02-02 16:31 ` Peter Xu
2021-02-02 16:44   ` Jason Gunthorpe
2021-02-02 17:05     ` Peter Xu
2021-02-02 17:13       ` Jason Gunthorpe
2021-02-03 12:43         ` Gal Pressman
2021-02-03 14:00           ` Jason Gunthorpe
2021-02-03 14:47             ` Gal Pressman

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