On Thu, Feb 26, 2015 at 8:00 PM, Stephen Warren <swarren@xxxxxxxxxxxxx> wrote:
> On 02/26/2015 10:42 AM, Russell King - ARM Linux wrote:
>>
>> On Thu, Feb 26, 2015 at 11:37:08AM +0100, Geert Uytterhoeven wrote:
>>>
>>> When trying to kexec into a new kernel on a platform where multiple CPU
>>> cores are present, but no SMP bringup code is available yet, the
>>> kexec_load system call fails with:
>>>
>>> kexec_load failed: Invalid argument
>>>
>>> The SMP test added to machine_kexec_prepare() in commit 2103f6cba61a8b8b
>>> ("ARM: 7807/1: kexec: validate CPU hotplug support") wants to prohibit
>>> kexec on SMP platforms where it cannot disable secondary CPUs.
>>> However, this test is too strict: if the secondary CPUs couldn't be
>>> enabled in the first place, there's no need to disable them later at
>>> kexec time. Hence skip the test in the absence of SMP bringup code.
>>
>>
>> Hmm. I don't think we should relax it in this manner - I think there's
>> an easier solution to this.
>>
>>> diff --git a/arch/arm/kernel/machine_kexec.c
>>> b/arch/arm/kernel/machine_kexec.c
>>> index de2b085ad7535da7..8bf3b7c098881b95 100644
>>> --- a/arch/arm/kernel/machine_kexec.c
>>> +++ b/arch/arm/kernel/machine_kexec.c
>>> @@ -46,7 +46,8 @@ int machine_kexec_prepare(struct kimage *image)
>>> * and implements CPU hotplug for the current HW. If not, we
>>> won't be
>>> * able to kexec reliably, so fail the prepare operation.
>>> */
>>> - if (num_possible_cpus() > 1 && !platform_can_cpu_hotplug())
>>> + if (num_possible_cpus() > 1 && platform_can_secondary_boot() &&
>>> + !platform_can_cpu_hotplug())
>>
>>
>> if (num_online_cpus() > 1 && !platform_can_cpu_hotplug())
>
> I can't remember the call stack here. Is num_online_cpus() guaranteed not to
> change from this point through to when the kexec actually happens?
Yeah, I had similar thoughts when I added the new test.
include/linux/cpumask.h:
* cpu_possible_mask- has bit 'cpu' set iff cpu is populatable
* cpu_present_mask - has bit 'cpu' set iff cpu is populated
* cpu_online_mask - has bit 'cpu' set iff cpu available to scheduler
* cpu_active_mask - has bit 'cpu' set iff cpu available to migration
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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