From: David Hildenbrand <david@redhat.com>
To: Baoquan He <bhe@redhat.com>, Andrew Morton <akpm@linux-foundation.org>
Cc: piliu@redhat.com, Anshuman Khandual <anshuman.khandual@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Bhupesh Sharma <bhsharma@redhat.com>,
linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org,
Russell King - ARM Linux admin <linux@armlinux.org.uk>,
linux-mm@kvack.org, James Morse <james.morse@arm.com>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image
Date: Tue, 21 Apr 2020 15:29:37 +0200 [thread overview]
Message-ID: <9a4eb1d7-33bf-8707-9c0c-1ca657c3e502@redhat.com> (raw)
In-Reply-To: <2525cc9c-3566-6275-105b-7f4af8f980bc@redhat.com>
>> ACPI SRAT is embeded into efi, need read out the rsdp pointer. If we don't
>> pass the efi, it won't get the SRAT table correctly, if I remember
>> correctly. Yeah, I remeber kvm guest can get memory hotplugged with
>> ACPI only, this won't happen on bare metal though. Need check carefully.
>> I have been using kvm guest with uefi firmwire recently.
>
> Yeah, I can imagine that bare metal is different. kvm only uses ACPI.
>
> I'm also asking because of virtio-mem. Memory added via virtio-mem is
> not part of any efi tables or whatsoever. So I assume the kexec kernel
> will not detect it automatically (good!), instead load the virtio-mem
> driver and let it add memory back to the system.
>
> I should probably play with kexec and virtio-mem once I have some spare
> cycles ... to find out what's broken and needs to be addressed :)
FWIW, I just gave virtio-mem and kexec/kdump a try.
a) kdump seems to work. Memory added by virtio-mem is getting dumped.
The kexec kernel only uses memory in the crash region. The virtio-mem
driver properly bails out due to is_kdump_kernel().
b) "kexec -s -l" seems to work fine. For now, the kernel does not seem
to get placed on virtio-mem memory (pure luck due to the left-to-right
search). Memory added by virtio-mem is not getting added to the e820
map. Once the virtio-mem driver comes back up in the kexec kernel, the
right memory is readded.
c) "kexec -c -l" does not work properly. All memory added by virtio-mem
is added to the e820 map, which is wrong. Memory that should not be
touched will be touched by the kexec kernel. I assume kexec-tools just
goes ahead and adds anything it can find in /proc/iomem (or
/sys/firmware/memmap/) to the e820 map of the new kernel.
Due to c), I assume all hotplugged memory (e.g., ACPI DIMMs) is
similarly added to the e820 map and, therefore, won't be able to be
onlined MOVABLE easily.
At least for virtio-mem, I would either have to
a) Not support "kexec -c -l". A viable option if we would be planning on
not supporting it either way in the long term. I could block this
in-kernel somehow eventually.
b) Teach kexec-tools to leave virtio-mem added memory alone. E.g., by
indicating it in /proc/iomem in a special way ("System RAM
(hotplugged)"/"System RAM (virtio-mem)").
Baoquan, any opinion on that?
--
Thanks,
David / dhildenb
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next prev parent reply other threads:[~2020-04-21 13:29 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 [this message]
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
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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