From: james.morse@arm•com (James Morse)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v7 17/16] arm64: hibernate: Refuse to hibernate if the boot cpu is offline
Date: Fri, 22 Apr 2016 16:32:19 +0100 [thread overview]
Message-ID: <571A4403.7090100@arm.com> (raw)
In-Reply-To: <20160422104148.GD10606@leverpostej>
Hi Mark, Lorenzo,
On 22/04/16 11:41, Mark Rutland wrote:
> On Thu, Apr 21, 2016 at 05:28:52PM +0100, Lorenzo Pieralisi wrote:
>> On Thu, Apr 21, 2016 at 01:33:35PM +0100, Mark Rutland wrote:
>>> On Thu, Apr 21, 2016 at 12:44:16PM +0100, Mark Rutland wrote:
>>>> On Wed, Apr 13, 2016 at 05:31:50PM +0100, James Morse wrote:
>>>>> It is important to hibernate/resume on the same CPU, otherwise we may
>>>>> change the cpu order or restore a big cpu's register state on a little
>>>>> cpu.
>>>>>
>>>>> We know cpu 0 is the cpu the firmware booted us on last time,
>>>>
>>>> This assumes that we only kexec from CPU0 also, which we will have to
>>>> enforce. For example, disable_nonboot_cpus() does not enforce this if
>>>> CPU0 has been hotplugged out.
>>>>
>>>> Otherwise, this kernel's CPU0 is not necessarily the CPU the FW booted
>>>> a kernel on.
>>>
>>> A better approach might be:
>>>
>>> * When going down for hibernate, store the physical CPU ID (e.g.
>>> MPIDR_EL1.Aff*) in the header for the hibernate image.
>>>
>>> * When restoring a hibernate image, first switch over to the CPU
>>> described in the header (rather than assuming CPU0).
>>>
>>> I think this is a matter of adding a new disable_non_hibernate_cpus()
>>> function (defaulting to disable_nonboot_cpus()), and overriding that in
>>> the arch code. Then that can be called in resume_target_kernel.
>>
>> Yes, it looks feasible at least by code inspection, given that it
>> requires changes in core code I wonder whether it is a restriction
>> that we can remove later or we want it in from the beginning (given
>> that the issue with kexec you mention above is not present in the
>> current kernel, hopefully not for long :)).
I think this will work, the arch-header read/write happens in the right order
for it to influence which cores get plugged out.
Curiously, migrate_to_reboot_cpu() would allow us to specify which cpu we want
to run on, but disable_nonboot_cpus() doesn't...
> So long as we're not tied to a specific ABI for the hibernate image then
> we should be fine to change that later; I agree that this can be a
> subsequent improvement.
>
> So long as we have a mechanism to detect that the hibernate image format
> changed, we should be OK to add stuff to it.
We only need to worry about this if we support resuming with a different kernel
version. I don't think we should yet, so patch 16 puts some build specific data
in the header so that even a rebuild of the same kernel will refuse to
hibernate/restore. This is roughly what the core code does if the arch doesn't
need the header. With this we are free to extend the header as we see fit.
(If a distribution wants to support different-kernel-resume, its a one line
change, and an awful lot of testing!)
One thing that really bugs me about different-kernel-resume is that if the
combination you try is not supported, the first hint you get is a regular login
screen, when you were expecting your precious in-memory data.
Thanks,
James
next prev parent reply other threads:[~2016-04-22 15:32 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-01 16:53 [PATCH v7 00/16] arm64: kernel: Add support for hibernate/suspend-to-disk James Morse
2016-04-01 16:53 ` [PATCH v7 01/16] arm64: KVM: Register CPU notifiers when the kernel runs at HYP James Morse
2016-04-18 16:10 ` Catalin Marinas
2016-04-19 8:58 ` James Morse
2016-04-19 14:39 ` Marc Zyngier
2016-04-01 16:53 ` [PATCH v7 02/16] arm64: Fold proc-macros.S into assembler.h James Morse
2016-04-18 16:11 ` Catalin Marinas
2016-04-01 16:53 ` [PATCH v7 03/16] arm64: Cleanup SCTLR flags James Morse
2016-04-19 14:44 ` Marc Zyngier
2016-04-01 16:53 ` [PATCH v7 04/16] arm64: kvm: Move the do_el2_call macro to a header file James Morse
2016-04-19 15:02 ` Marc Zyngier
2016-04-19 15:05 ` James Morse
2016-04-19 15:10 ` Marc Zyngier
2016-04-01 16:53 ` [PATCH v7 05/16] arm64: kvm: Move lr save/restore from do_el2_call into EL1 James Morse
2016-04-19 15:11 ` Marc Zyngier
2016-04-01 16:53 ` [PATCH v7 06/16] arm64: hyp/kvm: Extend hyp-stub API to allow function calls at EL2 James Morse
2016-04-19 15:22 ` Marc Zyngier
2016-04-01 16:53 ` [PATCH v7 07/16] arm64: kvm: allows kvm cpu hotplug James Morse
2016-04-19 16:03 ` Marc Zyngier
2016-04-19 17:37 ` James Morse
2016-04-20 10:29 ` AKASHI Takahiro
2016-04-20 11:19 ` James Morse
2016-04-20 10:37 ` Marc Zyngier
2016-04-20 11:19 ` James Morse
2016-04-20 11:46 ` Marc Zyngier
2016-04-25 8:41 ` AKASHI Takahiro
2016-04-25 9:16 ` James Morse
2016-04-25 9:28 ` Marc Zyngier
2016-04-01 16:53 ` [PATCH v7 08/16] arm64: kernel: Rework finisher callback out of __cpu_suspend_enter() James Morse
2016-04-18 17:20 ` Catalin Marinas
2016-04-01 16:53 ` [PATCH v7 09/16] arm64: Change cpu_resume() to enable mmu early then access sleep_sp by va James Morse
2016-04-20 16:24 ` Catalin Marinas
2016-04-01 16:53 ` [PATCH v7 10/16] arm64: kernel: Include _AC definition in page.h James Morse
2016-04-20 16:25 ` Catalin Marinas
2016-04-01 16:53 ` [PATCH v7 11/16] arm64: Promote KERNEL_START/KERNEL_END definitions to a header file James Morse
2016-04-20 16:26 ` Catalin Marinas
2016-04-01 16:53 ` [PATCH v7 12/16] arm64: Add new asm macro copy_page James Morse
2016-04-20 16:38 ` Catalin Marinas
2016-04-20 16:56 ` James Morse
2016-04-01 16:53 ` [PATCH v7 13/16] arm64: head.S: el2_setup() to accept sctlr_el1 as an argument James Morse
2016-04-20 17:12 ` Catalin Marinas
2016-04-20 17:35 ` James Morse
2016-04-22 10:36 ` Catalin Marinas
2016-04-01 16:53 ` [PATCH v7 14/16] PM / Hibernate: Call flush_icache_range() on pages restored in-place James Morse
2016-04-20 17:16 ` Catalin Marinas
2016-04-01 16:53 ` [PATCH v7 15/16] arm64: kernel: Add support for hibernate/suspend-to-disk James Morse
2016-04-22 10:29 ` Catalin Marinas
2016-04-25 9:19 ` James Morse
2016-04-01 16:53 ` [PATCH v7 16/16] arm64: hibernate: Prevent resume from a different kernel version James Morse
2016-04-10 12:16 ` Ard Biesheuvel
2016-04-13 16:35 ` James Morse
2016-04-13 16:31 ` [PATCH v7 17/16] arm64: hibernate: Refuse to hibernate if the boot cpu is offline James Morse
2016-04-21 11:33 ` Lorenzo Pieralisi
2016-04-21 11:44 ` Mark Rutland
2016-04-21 12:33 ` Mark Rutland
2016-04-21 16:28 ` Lorenzo Pieralisi
2016-04-22 10:41 ` Mark Rutland
2016-04-22 15:32 ` James Morse [this message]
2016-04-22 10:41 ` Catalin Marinas
2016-04-22 15:32 ` James Morse
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