linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: ebiederm@xmission.com (Eric W. Biederman)
To: James Morse <james.morse@arm.com>
Cc: kexec@lists.infradead.org,  linux-mm@kvack.org,
	 linux-arm-kernel@lists.infradead.org,
	 Anshuman Khandual <anshuman.khandual@arm.com>,
	 Catalin Marinas <catalin.marinas@arm.com>,
	 Bhupesh Sharma <bhsharma@redhat.com>,
	 Andrew Morton <akpm@linux-foundation.org>,
	 Will Deacon <will@kernel.org>
Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image
Date: Wed, 15 Apr 2020 15:33:43 -0500	[thread overview]
Message-ID: <87d088h4k8.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20200326180730.4754-2-james.morse@arm.com> (James Morse's message of "Thu, 26 Mar 2020 18:07:28 +0000")

James Morse <james.morse@arm.com> writes:

> An image loaded for kexec is not stored in place, instead its segments
> are scattered through memory, and are re-assembled when needed. In the
> meantime, the target memory may have been removed.
>
> Because mm is not aware that this memory is still in use, it allows it
> to be removed.
>
> Add a memory notifier to prevent the removal of memory regions that
> overlap with a loaded kexec image segment. e.g., when triggered from the
> Qemu console:
> | kexec_core: memory region in use
> | memory memory32: Offline failed.
>
> Signed-off-by: James Morse <james.morse@arm.com>

Given that we are talking about the destination pages for kexec
not where the loaded kernel is currently stored the description is
confusing.

Beyond that I think it would be better to simply unload the loaded
kernel at memory hotunplug time.  Usually somewhere in the loaded image
is a copy of the memory map at the time the kexec kernel was loaded.
That will invalidate the memory map as well.

All of this should be for a very brief window of a few seconds, as
the loaded kexec image is quite short.

So instead of failing in the notifier, if you could simply unload the
loaded image in the notifier I think that would be simpler and more
robust.  While still preventing the loaded image from falling over
when it starts executing.

Eric


  parent reply	other threads:[~2020-04-15 20:36 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-26 18:07 [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use James Morse
2020-03-26 18:07 ` [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image James Morse
2020-03-27  0:43   ` Anshuman Khandual
2020-03-27  2:54     ` Baoquan He
2020-03-27 15:46     ` James Morse
2020-03-27  2:34   ` Baoquan He
2020-03-27  9:30   ` David Hildenbrand
2020-03-27 16:56     ` James Morse
2020-03-27 17:06       ` David Hildenbrand
2020-03-27 18:07         ` James Morse
2020-03-27 18:52           ` David Hildenbrand
2020-03-30 13:00             ` James Morse
2020-03-30 13:13               ` David Hildenbrand
2020-03-30 17:17                 ` James Morse
2020-03-30 18:14                   ` David Hildenbrand
2020-04-10 19:10                     ` Andrew Morton
2020-04-11  3:44                       ` Baoquan He
2020-04-11  9:30                         ` Russell King - ARM Linux admin
2020-04-11  9:58                           ` David Hildenbrand
2020-04-12  5:35                           ` Baoquan He
2020-04-12  8:08                             ` Russell King - ARM Linux admin
2020-04-12 19:52                               ` Eric W. Biederman
2020-04-12 20:37                                 ` Bhupesh SHARMA
2020-04-13  2:37                                 ` Baoquan He
2020-04-13 13:15                                   ` Eric W. Biederman
2020-04-13 23:01                                     ` Andrew Morton
2020-04-14  6:13                                       ` Eric W. Biederman
2020-04-14  6:40                                     ` Baoquan He
2020-04-14  6:51                                       ` Baoquan He
2020-04-14  8:00                                       ` David Hildenbrand
2020-04-14  9:22                                         ` Baoquan He
2020-04-14  9:37                                           ` David Hildenbrand
2020-04-14 14:39                                             ` Baoquan He
2020-04-14 14:49                                               ` David Hildenbrand
2020-04-15  2:35                                                 ` Baoquan He
2020-04-16 13:31                                                   ` David Hildenbrand
2020-04-16 14:02                                                     ` Baoquan He
2020-04-16 14:09                                                       ` David Hildenbrand
2020-04-16 14:36                                                         ` Baoquan He
2020-04-16 14:47                                                           ` David Hildenbrand
2020-04-21 13:29                                                             ` David Hildenbrand
2020-04-21 13:57                                                               ` David Hildenbrand
2020-04-21 13:59                                                               ` Eric W. Biederman
2020-04-21 14:30                                                                 ` David Hildenbrand
2020-04-22  9:17                                                               ` Baoquan He
2020-04-22  9:24                                                                 ` David Hildenbrand
2020-04-22  9:57                                                                   ` Baoquan He
2020-04-22 10:05                                                                     ` David Hildenbrand
2020-04-22 10:36                                                                       ` Baoquan He
2020-04-14  9:16                                     ` Dave Young
2020-04-14  9:38                                       ` Dave Young
2020-04-14  7:05                       ` David Hildenbrand
2020-04-14 16:55                         ` James Morse
2020-04-14 17:41                           ` David Hildenbrand
2020-04-15 20:33   ` Eric W. Biederman [this message]
2020-04-22 12:28     ` James Morse
2020-04-22 15:25       ` Eric W. Biederman
2020-04-22 16:40         ` David Hildenbrand
2020-04-23 16:29           ` Eric W. Biederman
2020-04-24  7:39             ` David Hildenbrand
2020-04-24  7:41               ` David Hildenbrand
2020-05-01 16:55           ` James Morse
2020-03-26 18:07 ` [PATCH 2/3] mm/memory_hotplug: Allow arch override of non boot memory resource names James Morse
2020-03-27  9:59   ` David Hildenbrand
2020-03-27 15:39     ` James Morse
2020-03-30 13:23       ` David Hildenbrand
2020-03-30 17:17         ` James Morse
2020-04-02  5:49   ` Dave Young
2020-04-02  6:12     ` piliu
2020-04-14 17:21       ` James Morse
2020-04-15 20:36   ` Eric W. Biederman
2020-04-22 12:14     ` James Morse
2020-05-09  0:45   ` Andrew Morton
2020-05-11  8:35     ` David Hildenbrand
2020-03-26 18:07 ` [PATCH 3/3] arm64: memory: Give hotplug memory a different resource name James Morse
2020-03-30 19:01   ` David Hildenbrand
2020-04-15 20:37   ` Eric W. Biederman
2020-04-22 12:14     ` James Morse
2020-03-27  2:11 ` [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use Baoquan He
2020-03-27 15:40   ` James Morse
2020-03-27  9:27 ` David Hildenbrand
2020-03-27 15:42   ` James Morse
2020-03-30 13:18     ` David Hildenbrand
2020-03-30 13:55 ` Baoquan He
2020-03-30 17:17   ` James Morse
2020-03-31  3:46     ` Dave Young
2020-04-14 17:31       ` James Morse
2020-03-31  3:38 ` Dave Young
2020-04-15 20:29 ` Eric W. Biederman
2020-04-22 12:14   ` James Morse
2020-04-22 13:04     ` Eric W. Biederman
2020-04-22 15:40       ` James Morse

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=87d088h4k8.fsf@x220.int.ebiederm.org \
    --to=ebiederm@xmission.com \
    --cc=akpm@linux-foundation.org \
    --cc=anshuman.khandual@arm.com \
    --cc=bhsharma@redhat.com \
    --cc=catalin.marinas@arm.com \
    --cc=james.morse@arm.com \
    --cc=kexec@lists.infradead.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-mm@kvack.org \
    --cc=will@kernel.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).