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From: Andrea Arcangeli <aarcange@redhat.com>
To: Nadav Amit <namit@vmware.com>
Cc: Peter Xu <peterx@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-mm <linux-mm@kvack.org>,
	lkml <linux-kernel@vger.kernel.org>, Yu Zhao <yuzhao@google.com>,
	Andy Lutomirski <luto@kernel.org>,
	Pavel Emelyanov <xemul@openvz.org>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Mike Rapoport <rppt@linux.vnet.ibm.com>,
	Minchan Kim <minchan@kernel.org>, Will Deacon <will@kernel.org>,
	Mel Gorman <mgorman@suse.de>
Subject: Re: [RFC PATCH v2 1/2] mm/userfaultfd: fix memory corruption due to writeprotect
Date: Tue, 5 Jan 2021 14:45:47 -0500	[thread overview]
Message-ID: <X/TB6ztitnESl3qZ@redhat.com> (raw)
In-Reply-To: <BABCB1DE-C41E-4C3E-90D1-5893585FB68A@vmware.com>

On Tue, Jan 05, 2021 at 07:05:22PM +0000, Nadav Amit wrote:
> > On Jan 5, 2021, at 10:45 AM, Andrea Arcangeli <aarcange@redhat.com> wrote:
> > I just don't like to slow down a feature required in the future for
> > implementing postcopy live snapshotting or other snapshots to userland
> > processes (for the non-KVM case, also unprivileged by default if using
> > bounce buffers to feed the syscalls) that can be used by open source
> > hypervisors to beat proprietary hypervisors like vmware.
> 
> Ouch, that’s uncalled for. I am sure that you understand that I have no
> hidden agenda and we all have the same goal.

Ehm I never said you had an hidden agenda, so I'm not exactly why
you're accusing me of something I never said.

I merely pointed out one relevant justification for increasing kernel
complexity here by not slowing down clear_refs longstanding O(N)
clear_refs/softdirty feature and the recent uffd-wp O(1) feature, is
to be more competitive with proprietary software solutions, since
at least for uffd-wp, postcopy live snapshotting that the #1 use
case.

I never questioned your contribution or your preference, to be even
more explicit, it never crossed my mind that you have an hidden
agenda.

However since everyone already acked your patches and I'm not ok with
your patches because they will give a hit to KVM postcopy live
snapshotting and other container clear_refs users, I have to justify
why I NAK your patches and remaining competitive with proprietary
hypervisors is one of them, so I don't see what is wrong to state a
tangible end goal here.

Thanks,
Andrea


  reply	other threads:[~2021-01-05 19:47 UTC|newest]

Thread overview: 96+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-25  9:25 [RFC PATCH v2 0/2] mm: fix races due to deferred TLB flushes Nadav Amit
2020-12-25  9:25 ` [RFC PATCH v2 1/2] mm/userfaultfd: fix memory corruption due to writeprotect Nadav Amit
2021-01-04 12:22   ` Peter Zijlstra
2021-01-04 19:24     ` Andrea Arcangeli
2021-01-04 19:35       ` Nadav Amit
2021-01-04 20:19         ` Andrea Arcangeli
2021-01-04 20:39           ` Nadav Amit
2021-01-04 21:01             ` Andrea Arcangeli
2021-01-04 21:26               ` Nadav Amit
2021-01-05 18:45                 ` Andrea Arcangeli
2021-01-05 19:05                   ` Nadav Amit
2021-01-05 19:45                     ` Andrea Arcangeli [this message]
2021-01-05 20:06                       ` Nadav Amit
2021-01-05 21:06                         ` Andrea Arcangeli
2021-01-05 21:43                           ` Peter Xu
2021-01-05  8:13       ` Peter Zijlstra
2021-01-05  8:52         ` Nadav Amit
2021-01-05 14:26           ` Peter Zijlstra
2021-01-05  8:58       ` Peter Zijlstra
2021-01-05  9:22         ` Nadav Amit
2021-01-05 17:58         ` Andrea Arcangeli
2021-01-05 15:08   ` Peter Xu
2021-01-05 18:08     ` Andrea Arcangeli
2021-01-05 18:41       ` Peter Xu
2021-01-05 18:55         ` Andrea Arcangeli
2021-01-05 19:07     ` Nadav Amit
2021-01-05 19:43       ` Peter Xu
2020-12-25  9:25 ` [RFC PATCH v2 2/2] fs/task_mmu: acquire mmap_lock for write on soft-dirty cleanup Nadav Amit
2021-01-05 15:08   ` Will Deacon
2021-01-05 18:20   ` Andrea Arcangeli
2021-01-05 19:26     ` Nadav Amit
2021-01-05 20:39       ` Andrea Arcangeli
2021-01-05 21:20         ` Yu Zhao
2021-01-05 21:22         ` Nadav Amit
2021-01-05 22:16           ` Will Deacon
2021-01-06  0:29             ` Andrea Arcangeli
2021-01-06  0:02           ` Andrea Arcangeli
2021-01-07 20:04           ` [PATCH 0/2] page_count can't be used to decide when wp_page_copy Andrea Arcangeli
2021-01-07 20:04             ` [PATCH 1/2] mm: proc: Invalidate TLB after clearing soft-dirty page state Andrea Arcangeli
2021-01-07 20:04             ` [PATCH 2/2] mm: soft_dirty: userfaultfd: introduce wrprotect_tlb_flush_pending Andrea Arcangeli
2021-01-07 20:17               ` Linus Torvalds
2021-01-07 20:25                 ` Linus Torvalds
2021-01-07 20:58                 ` Andrea Arcangeli
2021-01-07 21:29                   ` Linus Torvalds
2021-01-07 21:53                     ` John Hubbard
2021-01-07 22:00                       ` Linus Torvalds
2021-01-07 22:14                         ` John Hubbard
2021-01-07 22:20                           ` Linus Torvalds
2021-01-07 22:24                             ` Linus Torvalds
2021-01-07 22:37                               ` John Hubbard
2021-01-15 11:27                       ` Jan Kara
2021-01-07 22:31                     ` Andrea Arcangeli
2021-01-07 22:42                       ` Linus Torvalds
2021-01-07 22:51                         ` Linus Torvalds
2021-01-07 23:48                           ` Andrea Arcangeli
2021-01-08  0:25                             ` Linus Torvalds
2021-01-08 12:48                               ` Will Deacon
2021-01-08 16:14                                 ` Andrea Arcangeli
2021-01-08 17:39                                   ` Linus Torvalds
2021-01-08 17:53                                     ` Andrea Arcangeli
2021-01-08 19:25                                       ` Linus Torvalds
2021-01-09  0:12                                         ` Andrea Arcangeli
2021-01-08 17:30                                 ` Linus Torvalds
2021-01-07 23:28                         ` Andrea Arcangeli
2021-01-07 21:36               ` kernel test robot
2021-01-07 20:25             ` [PATCH 0/2] page_count can't be used to decide when wp_page_copy Jason Gunthorpe
2021-01-07 20:32               ` Linus Torvalds
2021-01-07 21:05                 ` Linus Torvalds
2021-01-07 22:02                   ` Andrea Arcangeli
2021-01-07 22:17                     ` Linus Torvalds
2021-01-07 22:56                       ` Andrea Arcangeli
2021-01-09 19:32                   ` Matthew Wilcox
2021-01-09 19:46                     ` Linus Torvalds
2021-01-15 14:30                       ` Jan Kara
2021-01-07 21:54                 ` Andrea Arcangeli
2021-01-07 21:45               ` Andrea Arcangeli
2021-01-08 13:36                 ` Jason Gunthorpe
2021-01-08 17:00                   ` Andrea Arcangeli
2021-01-08 18:19                     ` Jason Gunthorpe
2021-01-08 18:31                       ` Andy Lutomirski
2021-01-08 18:38                         ` Linus Torvalds
2021-01-08 23:34                         ` Andrea Arcangeli
2021-01-09 19:03                           ` Andy Lutomirski
2021-01-09 19:15                             ` Linus Torvalds
2021-01-08 18:59                       ` Linus Torvalds
2021-01-08 22:43                       ` Andrea Arcangeli
2021-01-09  0:42                         ` Jason Gunthorpe
2021-01-09  2:50                           ` Andrea Arcangeli
2021-01-11 14:30                             ` Jason Gunthorpe
2021-01-13 21:56                           ` Jerome Glisse
2021-01-13 23:39                             ` Jason Gunthorpe
2021-01-14  2:35                               ` Jerome Glisse
     [not found]                     ` <20210109034958.6928-1-hdanton@sina.com>
2021-01-11 14:39                       ` Jason Gunthorpe
2021-01-05 21:55         ` [RFC PATCH v2 2/2] fs/task_mmu: acquire mmap_lock for write on soft-dirty cleanup Peter Xu
2021-03-02 22:13 ` [RFC PATCH v2 0/2] mm: fix races due to deferred TLB flushes Peter Xu
2021-03-02 22:14   ` Nadav Amit

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