From: David Hildenbrand <david@redhat.com>
To: James Morse <james.morse@arm.com>
Cc: kexec@lists.infradead.org, linux-mm@kvack.org,
linux-arm-kernel@lists.infradead.org,
Eric Biederman <ebiederm@xmission.com>,
Andrew Morton <akpm@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Anshuman Khandual <anshuman.khandual@arm.com>,
Bhupesh Sharma <bhsharma@redhat.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH 2/3] mm/memory_hotplug: Allow arch override of non boot memory resource names
Date: Mon, 30 Mar 2020 15:23:01 +0200 [thread overview]
Message-ID: <1090cc16-fa6b-8dd2-8c41-22136f733f00@redhat.com> (raw)
In-Reply-To: <25aa3f43-5aa9-653f-0910-dd7b75527e08@arm.com>
>>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
>>> index 0a54ffac8c68..69b03dd7fc74 100644
>>> --- a/mm/memory_hotplug.c
>>> +++ b/mm/memory_hotplug.c
>>> @@ -42,6 +42,10 @@
>>> #include "internal.h"
>>> #include "shuffle.h"
>>>
>>> +#ifndef MEMORY_HOTPLUG_RES_NAME
>>> +#define MEMORY_HOTPLUG_RES_NAME "System RAM"
>>> +#endif
>>
>> So I assume changing this for all architectures would result in some
>> user space tool breaking? Are we aware of any?
>
> Last time we had to touch arm64's /proc/iomem strings I went through debian's
> codesearch for stuff that reads it, kexec-tools was the only thing that parsed
> it in anger. (From memory, the other tools were looking for PCIe windows to do
> firmware flashing..)
>
> Looking again, having qualifiers on the end of 'System RAM' looks like it could
> confuse 's390-tools's detect_mem_chunks parser.
Good to know, we should find out if this could work.
>
> It looks like the strings that come out of 'FIRMWARE_MEMMAP' are a duplicate set.
>
>
>> I do wonder if we should simply change it for all architectures if possible.
>
> If its possible that would be great. But I suspect that ship has sailed,
> changing it on other architectures could break some fragile parsing code.
I assume any parser has to be prepared for new types showing up.
Otherwise these would not be future proof. The question is if a common
prefix is problematic.
E.g., Use "Hotplugged System RAM" instead of "System RAM (hotplug)"
>
> I'm wary of changing it on arm64, the only thing that makes it tolerable is that
> memory hot-add was relatively recently merged, and we don't anticipate it being
> widely used until you can remove memory as well.
>
> Changing it on arm64 is to prevent today's versions of kexec-tools from
> accidentally placing the new kernel in memory that wasn't described at boot.
> This leads to an unhandled exception during boot[0] because the kernel can't
> access itself via the mapping of all memory. (hotpluggable regions are only
> discovered by suitably configured ACPI systems much later)
I want the very same for virtio-mem (initially x86-only, but later open
for all archs). Can also be interesting for Hyper-V. kexec should not
try to use hotplugged memory as kexec target, as memory blocks can be
partially inaccessible.
Of course, I can provide an interface to override the name via
add_memory(), but having it on all architectures handled in a similar
way right from the start would be nicer.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-03-30 13:23 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 [this message]
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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