From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH V2] ARM: EXYNOS: Fix hotplug when CPUs boot in HYP mode
Date: Wed, 08 May 2013 13:57:26 +0100 [thread overview]
Message-ID: <518A4BB6.5020801@arm.com> (raw)
In-Reply-To: <CAHuqX+GOLO_H81B3bwcqF7Sp0srctBn+6J9mbRF_kbPRTXC-ng@mail.gmail.com>
On 08/05/13 13:23, Giridhar Maruthy wrote:
> On 7 May 2013 14:25, Marc Zyngier <marc.zyngier@arm•com> wrote:
>> On 07/05/13 06:54, Giridhar Maruthy wrote:
>>> This patch is a modification from the Christoffer Dall's u-boot
>>> patch. This is required to put the secondary processors in hyp
>>> mode during cpu hotplug when u-boot is no longer alive.
>>>
>>> Marc Zyngier suggested this logic to go into firmware or, u-boot
>>> putting a trampoline code into a page /memreserve/d by DT. But
>>> this seemed to have a problem. Once the cpu is hotplugged in
>>> runtime, the control is in ROM code and waits for event.
>>> Kernel provides a return address in kernel to which the processor
>>> jumps once it gets an event. If the control branches to the
>>> trampoline code here, this trampoline code has no kernel return
>>> address.
>>>
>>> Someone with better logic or better placement of this logic
>>> elsewhere is welcome.
>>
>> What prevents you from writing the kernel address in the memreserved
>> page? Some obvious location, like the last word of the page? You only
>> have to do it once (from the boot CPU, for example).
>>
>> Or did I miss something else?
>
> Thanks Marc, I think I understand now.
>
> I guess I also need to put the primary cpu boot mode into a temporary location.
Indeed. You'll need that for your secondaries to enter in the same mode
as the primary.
M.
--
Jazz is not dead. It just smells funny...
prev parent reply other threads:[~2013-05-08 12:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-07 5:51 [RFC PATCH V2] ARM: EXYNOS: Fix hotplug when CPUs boot in HYP mode giridhar.maruthy at linaro.org
2013-05-07 5:54 ` Giridhar Maruthy
2013-05-07 8:55 ` Marc Zyngier
2013-05-08 12:23 ` Giridhar Maruthy
2013-05-08 12:57 ` Marc Zyngier [this message]
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