From: David Hildenbrand <david@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Nadav Amit <namit@vmware.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Hugh Dickins <hughd@google.com>,
David Rientjes <rientjes@google.com>,
Shakeel Butt <shakeelb@google.com>,
John Hubbard <jhubbard@nvidia.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Yang Shi <shy828301@gmail.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@infradead.org>,
Vlastimil Babka <vbabka@suse.cz>, Jann Horn <jannh@google.com>,
Michal Hocko <mhocko@kernel.org>, Rik van Riel <riel@surriel.com>,
Roman Gushchin <guro@fb.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Peter Xu <peterx@redhat.com>, Donald Dutile <ddutile@redhat.com>,
Christoph Hellwig <hch@lst.de>, Oleg Nesterov <oleg@redhat.com>,
Jan Kara <jack@suse.cz>, Linux-MM <linux-mm@kvack.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>
Subject: Re: [PATCH v1 06/11] mm: support GUP-triggered unsharing via FAULT_FLAG_UNSHARE (!hugetlb)
Date: Wed, 22 Dec 2021 09:30:04 +0100 [thread overview]
Message-ID: <e6d5d38c-c309-5646-84e2-5840fc037a5c@redhat.com> (raw)
In-Reply-To: <20211221235916.GI1432915@nvidia.com>
On 22.12.21 00:59, Jason Gunthorpe wrote:
> On Tue, Dec 21, 2021 at 06:40:30PM +0100, David Hildenbrand wrote:
>
>> What adds complexity to correctly maintain the "exclusive" state are at
>> least:
>> * KSM (might be harder, have to think about it)
>
> I know little about it, but isn't KSM like fork where it is trying to
> WP pages with the intention of copying them? Shouldn't KSM completely
> reject WP'ing a page that is under any kind of writable GUP?
I think KSM will, similar to fork(), always have to try removing
PageAnonExclusive() while synchronizing against concurrent GUP pins. If
that fails, the page cannot be converted to KSM and consequently not be
shared.
That will need some rework of KSM AFAIU, but shouldn't be impossible to do.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-12-22 8:30 UTC|newest]
Thread overview: 137+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-17 11:30 [PATCH v1 00/11] mm: COW fixes part 1: fix the COW security issue for THP and hugetlb David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 01/11] seqlock: provide lockdep-free raw_seqcount_t variant David Hildenbrand
2021-12-17 17:02 ` Nadav Amit
2021-12-17 17:29 ` David Hildenbrand
2021-12-17 17:49 ` David Hildenbrand
2021-12-17 18:01 ` Nadav Amit
2021-12-17 21:28 ` Thomas Gleixner
2021-12-17 22:02 ` David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 02/11] mm: thp: consolidate mapcount logic on THP split David Hildenbrand
2021-12-17 19:06 ` Yang Shi
2021-12-18 14:24 ` Kirill A. Shutemov
2021-12-17 11:30 ` [PATCH v1 03/11] mm: simplify hugetlb and file-THP handling in __page_mapcount() David Hildenbrand
2021-12-17 17:16 ` Nadav Amit
2021-12-17 17:30 ` David Hildenbrand
2021-12-17 18:06 ` Mike Kravetz
2021-12-17 18:11 ` David Hildenbrand
2021-12-17 19:07 ` Yang Shi
2021-12-18 14:31 ` Kirill A. Shutemov
2021-12-17 11:30 ` [PATCH v1 04/11] mm: thp: simlify total_mapcount() David Hildenbrand
2021-12-17 19:12 ` Yang Shi
2021-12-18 14:35 ` Kirill A. Shutemov
2021-12-17 11:30 ` [PATCH v1 05/11] mm: thp: allow for reading the THP mapcount atomically via a raw_seqlock_t David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 06/11] mm: support GUP-triggered unsharing via FAULT_FLAG_UNSHARE (!hugetlb) David Hildenbrand
2021-12-17 19:04 ` Linus Torvalds
2021-12-17 19:22 ` Linus Torvalds
2021-12-17 20:17 ` David Hildenbrand
2021-12-17 20:36 ` Linus Torvalds
2021-12-17 20:39 ` Linus Torvalds
2021-12-17 20:43 ` Linus Torvalds
2021-12-17 20:42 ` David Hildenbrand
2021-12-17 20:45 ` Linus Torvalds
2021-12-18 22:52 ` Kirill A. Shutemov
2021-12-18 23:05 ` Linus Torvalds
2021-12-17 20:47 ` Jason Gunthorpe
2021-12-17 20:56 ` Linus Torvalds
2021-12-17 21:17 ` David Hildenbrand
2021-12-17 21:04 ` David Hildenbrand
2021-12-18 0:50 ` Jason Gunthorpe
2021-12-17 21:15 ` Nadav Amit
2021-12-17 21:20 ` David Hildenbrand
2021-12-18 0:50 ` Jason Gunthorpe
2021-12-18 1:53 ` Linus Torvalds
2021-12-18 2:17 ` Linus Torvalds
2021-12-18 2:42 ` Linus Torvalds
2021-12-18 3:36 ` Linus Torvalds
2021-12-18 10:06 ` David Hildenbrand
2021-12-18 3:05 ` Jason Gunthorpe
2021-12-18 3:30 ` Nadav Amit
2021-12-18 3:38 ` Linus Torvalds
2021-12-18 18:42 ` Jason Gunthorpe
2021-12-18 18:49 ` David Hildenbrand
2021-12-18 21:48 ` Nadav Amit
2021-12-18 22:53 ` Linus Torvalds
2021-12-19 0:19 ` Nadav Amit
2021-12-19 0:35 ` Linus Torvalds
2021-12-19 6:02 ` Nadav Amit
2021-12-19 8:01 ` John Hubbard
2021-12-19 11:30 ` Matthew Wilcox
2021-12-19 17:27 ` Linus Torvalds
2021-12-19 17:44 ` David Hildenbrand
2021-12-19 17:44 ` Linus Torvalds
2021-12-19 17:59 ` David Hildenbrand
2021-12-19 21:12 ` Matthew Wilcox
2021-12-19 21:27 ` Linus Torvalds
2021-12-19 21:47 ` Matthew Wilcox
2021-12-19 21:53 ` Linus Torvalds
2021-12-19 22:02 ` Matthew Wilcox
2021-12-19 22:12 ` Linus Torvalds
2021-12-19 22:26 ` Matthew Wilcox
2021-12-20 18:37 ` Matthew Wilcox
2021-12-20 18:52 ` Matthew Wilcox
2021-12-20 19:38 ` Linus Torvalds
2021-12-20 19:15 ` Linus Torvalds
2021-12-20 21:02 ` Matthew Wilcox
2021-12-20 21:27 ` Linus Torvalds
2021-12-21 1:03 ` Jason Gunthorpe
2021-12-21 3:29 ` Matthew Wilcox
2021-12-21 8:58 ` David Hildenbrand
2021-12-21 14:28 ` Jason Gunthorpe
2021-12-21 15:19 ` David Hildenbrand
2021-12-21 23:54 ` Jason Gunthorpe
2021-12-21 17:05 ` Linus Torvalds
2021-12-21 17:40 ` David Hildenbrand
2021-12-21 18:00 ` Linus Torvalds
2021-12-21 18:28 ` David Hildenbrand
2021-12-21 21:11 ` John Hubbard
2021-12-21 18:07 ` Jan Kara
2021-12-21 18:30 ` Linus Torvalds
2021-12-21 18:51 ` David Hildenbrand
2021-12-21 18:58 ` Linus Torvalds
2021-12-21 21:16 ` John Hubbard
2021-12-21 19:07 ` Jason Gunthorpe
2021-12-22 8:51 ` David Hildenbrand
2021-12-22 9:58 ` David Hildenbrand
2021-12-22 12:41 ` Jan Kara
2021-12-22 13:09 ` David Hildenbrand
2021-12-22 14:42 ` Jan Kara
2021-12-22 14:48 ` David Hildenbrand
2021-12-22 16:08 ` Jan Kara
2021-12-22 16:44 ` Matthew Wilcox
2021-12-22 18:40 ` Linus Torvalds
2021-12-23 12:54 ` Jan Kara
2021-12-23 17:18 ` Linus Torvalds
2021-12-23 0:21 ` Matthew Wilcox
2021-12-24 2:53 ` Jason Gunthorpe
2021-12-24 4:53 ` Matthew Wilcox
2022-01-04 0:33 ` Jason Gunthorpe
2021-12-21 23:59 ` Jason Gunthorpe
2021-12-22 8:30 ` David Hildenbrand [this message]
2021-12-22 12:44 ` Jan Kara
2021-12-17 20:45 ` David Hildenbrand
2021-12-17 20:51 ` Linus Torvalds
2021-12-17 20:55 ` David Hildenbrand
2021-12-17 21:36 ` Linus Torvalds
2021-12-17 21:47 ` David Hildenbrand
2021-12-17 21:50 ` Linus Torvalds
2021-12-17 22:29 ` David Hildenbrand
2021-12-17 22:58 ` Linus Torvalds
2021-12-17 23:29 ` David Hildenbrand
2021-12-17 23:53 ` Nadav Amit
2021-12-18 4:02 ` Linus Torvalds
2021-12-18 4:52 ` Nadav Amit
2021-12-18 5:03 ` Matthew Wilcox
2021-12-18 5:23 ` Nadav Amit
2021-12-18 18:37 ` Linus Torvalds
2021-12-17 22:18 ` Linus Torvalds
2021-12-17 22:43 ` David Hildenbrand
2021-12-17 23:20 ` Linus Torvalds
2021-12-18 9:57 ` David Hildenbrand
2021-12-18 19:21 ` Linus Torvalds
2021-12-18 19:52 ` Linus Torvalds
2021-12-19 8:43 ` David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 07/11] mm: gup: trigger unsharing via FAULT_FLAG_UNSHARE when required (!hugetlb) David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 08/11] mm: hugetlb: support GUP-triggered unsharing via FAULT_FLAG_UNSHARE David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 09/11] mm: gup: trigger unsharing via FAULT_FLAG_UNSHARE when required (hugetlb) David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 10/11] mm: thp: introduce and use page_trans_huge_anon_shared() David Hildenbrand
2021-12-17 11:30 ` [PATCH v1 11/11] selftests/vm: add tests for the known COW security issues David Hildenbrand
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