linux-kernel - Re: [patch] KVM: T60 resume fix

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Message-ID: <45EBD9BC.4030801@qumranet.com>
Date:	Mon, 05 Mar 2007 10:50:04 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Pavel Machek <pavel@....cz>, Adrian Bunk <bunk@...sta.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Michael S. Tsirkin" <mst@...lanox.co.il>,
	Thomas Gleixner <tglx@...utronix.de>, linux-pm@...ts.osdl.org,
	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	Daniel Walker <dwalker@...sta.com>, Len Brown <lenb@...nel.org>
Subject: Re: [patch] KVM: T60 resume fix

Ingo Molnar wrote:
> * Avi Kivity <avi@...ranet.com> wrote:
>
>   
>>> my T60 laptop does not resume correctly due to KVM attempting to 
>>> send an IPI to a CPU that might be down (or not up yet). (Doing so 
>>> also triggers the send_IPI_mask_bitmask() warning in 
>>> arch/i386/kernel/smp.c, line 732.)
>>>
>>> with this fix applied my laptop does not hang during resume.
>>>
>>> [ KVM will have to disable/enable virtualization on the CPU itself 
>>>  that goes down / comes up, not via an IPI sent from the requesting
>>> CPU. ]
>>>       
>
>   
>> That is already CPU_ONLINE in my tree (and in the pull request sent to 
>> Linus a couple of days ago).
>>     
>
> that solves the resume problem - but doesnt solve the CPU_DEAD issue of 
> sending an IPI to an already offline CPU. Might be a better idea to do 
> it in CPU_DOWN_PREPARE? (and then to also add a CPU_DOWN_FAILED branch?)
>
> 	

Mainline now has DOWN_PREPARE and UP_CANCELED calling 
->hardware_disable(), and ONLINE calling ->hardware_enabled().  What 
tree are you looking at?

[but I do see the need for DOWN_FAILED now. Off to find a resumable 
machine...]


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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