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

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Date:	Mon, 11 Mar 2013 16:12:52 +0200
From:	Gleb Natapov <gleb@...hat.com>
To:	Jan Kiszka <jan.kiszka@...mens.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 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.

--
			Gleb.
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