linux-kernel - Re: [PATCH] x86: kvm: reset the bootstrap processor when it gets an INIT

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Message-ID: <513DE7DC.8020609@siemens.com>
Date:	Mon, 11 Mar 2013 15:19:08 +0100
From:	Jan Kiszka <jan.kiszka@...mens.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	Paolo Bonzini <pbonzini@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"mtosatti@...hat.com" <mtosatti@...hat.com>
Subject: Re: [PATCH] x86: kvm: reset the bootstrap processor when it gets
 an INIT

On 2013-03-11 15:12, Gleb Natapov wrote:
> On Mon, Mar 11, 2013 at 03:10:45PM +0100, Jan Kiszka wrote:
>> On 2013-03-11 15:09, Gleb Natapov wrote:
>>> On Mon, Mar 11, 2013 at 03:06:18PM +0100, Jan Kiszka wrote:
>>>> On 2013-03-11 15:05, Gleb Natapov wrote:
>>>>> On Mon, Mar 11, 2013 at 03:01:40PM +0100, Jan Kiszka wrote:
>>>>>>> We are not moving away from mp_state, we are moving away from using
>>>>>>> mp_state for signaling because with nested virt INIT does not always
>>>>>>> change mp_state, not only that it can change mp_state long after signal
>>>>>>> is received after vmx off is done.
>>>>>>
>>>>>> Right.
>>>>>>
>>>>>> BTW, for that to happen, we will also need to influence the INIT level.
>>>>>> Unless I misread the spec, INIT is blocked while in root mode, and if
>>>>>> you deassert INIT before leaving root (vmxoff, vmenter), nothing
>>>>>> actually happens. So what matters is the INIT signal level at the exit
>>>>>> of root mode.
>>>>>>
>>>>> You are talking about INIT# signal received via CPU pin, right? I think
>>>>> INIT send by IPI cannot go away.
>>>>
>>>> Why shouldn't it? Besides edge, there is also level-triggered INIT.
>>>>
>>> OK, so level-triggered INIT can be de-asserted what about edge triggered
>>> one? :)
>>
>> It should be lost while in root mode.
>>
> Ah, that's great. Removes some potential complications.

Again, that's my interpretation. I didn't check this against real HW
yet. It just makes most sense, given what I read.

Jan

-- 
Siemens AG, Corporate Technology, CT RTC ITP SDP-DE
Corporate Competence Center Embedded Linux
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