linux-kernel - Re: [PATCH] Fix emergency_restart (sysrq-b) with kvm loaded on Intel hosts

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Date:	Mon, 25 Aug 2008 11:30:20 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Avi Kivity <avi@...ranet.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] Fix emergency_restart (sysrq-b) with kvm loaded on
	Intel hosts


* Avi Kivity <avi@...ranet.com> wrote:

> Ingo Molnar wrote:
>> * Avi Kivity <avi@...ranet.com> wrote:
>>
>>   
>>> Enabling Intel VT has the curious side effect whereby the INIT signal 
>>> is blocked.  Rather than comment on the wisdom of this side effect,  
>>> this patch adds an emergency restart reboot notifier, and modifies 
>>> the kvm reboot notifier to disable VT on emergency reboot.
>>>     
>>
>> looks good to me - i was bitten by that problem on a testbox.
>>   
>
> I'm a little worried about making emergency restart more complex.
>
> Another thing that worries me is that emergency_restart() doesn't 
> reset the box -- it sends INIT.  We could do better by using the ACPI 
> FADT reset register (hopefully that's connected to RESET).

reboot was always a bit fragile - i think we should only do that if we 
find a box where the FADT reset works better than the first-wave 
approaches we try.

> Which seems to be what we want? Maybe we should just try acpi_reboot() 
> before the other stuff.

perhaps in a separate commit, for v2.6.28 at the earliest.

	Ingo
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