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From: James Morse <james.morse@arm.com>
To: "Eric W. Biederman" <ebiederm@xmission.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,
	Andrew Morton <akpm@linux-foundation.org>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 3/3] arm64: memory: Give hotplug memory a different resource name
Date: Wed, 22 Apr 2020 13:14:32 +0100	[thread overview]
Message-ID: <56c17c4e-fab4-5941-2239-e2aa77c8733d@arm.com> (raw)
In-Reply-To: <87v9m0fptf.fsf@x220.int.ebiederm.org>

Hi Eric,

On 15/04/2020 21:37, Eric W. Biederman wrote:
> James Morse <james.morse@arm.com> writes:
> 
>> If kexec chooses to place the kernel in a memory region that was
>> added after boot, we fail to boot as the kernel is running from a
>> location that is not described as memory by the UEFI memory map or
>> the original DT.
>>
>> To prevent unaware user-space kexec from doing this accidentally,
>> give these regions a different name.
> 
> Please fix the problem and don't hack around it.

The problem is firmware didn't describe memory that wasn't present at boot.

arm64 relies on the firmware description of memory well before it can go poking around in
ACPI to find out where extra memory was added to the system.

We already need kexec to not overwrite in-memory structures left by firmware. (like, the
memory map). We do this by naming them reserved in /proc/iomem.

Doing the same for hotadded memory means existing kexec user-space can't do this
accidentally. The shape of /proc/iomem is the only trick in the book for arm64's kexec
userspace, as its the only thing it looks at.



Thanks,

James






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      reply	other threads:[~2020-04-22 12:14 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20200326180730.4754-1-james.morse@arm.com>
     [not found] ` <20200330135522.GE6352@MiWiFi-R3L-srv>
     [not found]   ` <2bdfbb1c-49da-d476-4a38-f91937105ae3@arm.com>
     [not found]     ` <20200331034612.GB83248@dhcp-128-65.nay.redhat.com>
2020-04-14 17:31       ` [PATCH 0/3] kexec/memory_hotplug: Prevent removal and accidental use James Morse
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
     [not found] ` <20200326180730.4754-2-james.morse@arm.com>
     [not found]   ` <321e6bf7-e898-7701-dd60-6c25237ff9cd@redhat.com>
     [not found]     ` <a21d90ea-2566-a2bc-ad2f-6464a416c97f@arm.com>
     [not found]       ` <9cb4ea0d-34c3-de42-4b3f-ee25a59c4835@redhat.com>
     [not found]         ` <b0443908-e36f-9bc4-4a8a-4206cb782d4b@arm.com>
     [not found]           ` <72672e2c-a57a-8df9-0cff-8035cbce7740@redhat.com>
     [not found]             ` <34274b02-60ba-eb78-eacd-6dc1146ed3cd@arm.com>
     [not found]               ` <80e4d1d7-f493-3f66-f700-86f18002d692@redhat.com>
     [not found]                 ` <dfacf85f-d79d-8742-7a13-1ac0a67bad04@arm.com>
     [not found]                   ` <ba481c82-c69e-043c-4b66-2d2c7732cf07@redhat.com>
2020-04-10 19:10                     ` [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image 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
     [not found] ` <20200326180730.4754-3-james.morse@arm.com>
2020-04-02  5:49   ` [PATCH 2/3] mm/memory_hotplug: Allow arch override of non boot memory resource names 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
     [not found] ` <20200326180730.4754-4-james.morse@arm.com>
2020-04-15 20:37   ` [PATCH 3/3] arm64: memory: Give hotplug memory a different resource name Eric W. Biederman
2020-04-22 12:14     ` James Morse [this message]

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