From: Dave Young <dyoung@redhat.com>
To: James Morse <james.morse@arm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Bhupesh Sharma <bhsharma@redhat.com>,
kexec@lists.infradead.org, linux-mm@kvack.org,
Eric Biederman <ebiederm@xmission.com>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use
Date: Tue, 31 Mar 2020 11:38:27 +0800 [thread overview]
Message-ID: <20200331033827.GA83248@dhcp-128-65.nay.redhat.com> (raw)
In-Reply-To: <20200326180730.4754-1-james.morse@arm.com>
Hi James,
On 03/26/20 at 06:07pm, James Morse wrote:
> Hello!
>
> arm64 recently queued support for memory hotremove, which led to some
> new corner cases for kexec.
>
> If the kexec segments are loaded for a removable region, that region may
> be removed before kexec actually occurs. This causes the first kernel to
> lockup when applying the relocations. (I've triggered this on x86 too).
Does a kexec reload work for your case? If yes then I would suggest to
do it in userspace, for example have a udev rule to reload kexec if
needed.
Actually we have a rule to restart kdump loading, but not for kexec, it
sounds also need a service to load kexec, and an udev rule to reload for
memory hotplug.
>
> The first patch adds a memory notifier for kexec so that it can refuse
> to allow in-use regions to be taken offline.
>
>
> This doesn't solve the problem for arm64, where the new kernel must
> initially rely on the data structures from the first boot to describe
> memory. These don't describe hotpluggable memory.
> If kexec places the kernel in one of these regions, it must also provide
> a DT that describes the region in which the kernel was mapped as memory.
> (and somehow ensure its always present in the future...)
>
> To prevent this from happening accidentally with unaware user-space,
> patches two and three allow arm64 to give these regions a different
> name.
>
> This is a change in behaviour for arm64 as memory hotadd and hotremove
> were added separately.
>
>
> I haven't tried kdump.
> Unaware kdump from user-space probably won't describe the hotplug
> regions if the name is different, which saves us from problems if
> the memory is no longer present at kdump time, but means the vmcore
> is incomplete.
>
>
> These patches are based on arm64's for-next/core branch, but can all
> be merged independently.
>
> Thanks,
>
> James Morse (3):
> kexec: Prevent removal of memory in use by a loaded kexec image
> mm/memory_hotplug: Allow arch override of non boot memory resource
> names
> arm64: memory: Give hotplug memory a different resource name
>
> arch/arm64/include/asm/memory.h | 11 +++++++
> kernel/kexec_core.c | 56 +++++++++++++++++++++++++++++++++
> mm/memory_hotplug.c | 6 +++-
> 3 files changed, 72 insertions(+), 1 deletion(-)
>
> --
> 2.25.1
>
>
> _______________________________________________
> kexec mailing list
> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec
>
Thanks
Dave
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next prev parent reply other threads:[~2020-03-31 3:38 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
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 [this message]
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
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