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

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Message-ID: <20130311193003.GC14689@redhat.com>
Date:	Mon, 11 Mar 2013 21:30:03 +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 08:01:30PM +0100, Jan Kiszka wrote:
> On 2013-03-11 19:51, Gleb Natapov wrote:
> >>> On Intel:
> >>> CPU 1                          CPU 2 in a guest mode
> >>> send INIT
> >>> send SIPI
> >>>                                 INIT vmexit
> >>>                                 vmxoff
> >>>                                 reset and start from SIPI vector
> >>
> >> Is SIPI sticky as well, even if the CPU is not in the wait-for-SIPI
> >> state (but runnable and in vmxon) while receiving it?
> >>
> > That what they seams to be saying:
> >  However, an INIT and SIPI interrupts sent to a CPU during time when
> >  it is in a VMX mode are remembered and delivered, perhaps hours later,
> >  when the CPU exits the VMX mode
> > 
> > Otherwise their exploit will not work.
> 
> Very weird, specifically as SIPI is not just a binary event but carries
> payload. Will another SIPI event overwrite the previously "saved"
> vector? We are deep into an underspecified area...
My guess is that VMX INIT blocking is done by the same mechanism as
INIT blocking during SMM. Obviously after exit from SMM pending
INIT/SIPI have to be processed.

--
			Gleb.
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