Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753801Ab3CKRl7 (ORCPT ); Mon, 11 Mar 2013 13:41:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26789 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751379Ab3CKRl6 (ORCPT ); Mon, 11 Mar 2013 13:41:58 -0400 Date: Mon, 11 Mar 2013 19:41:55 +0200 From: Gleb Natapov To: Jan Kiszka Cc: Paolo Bonzini , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "mtosatti@redhat.com" Subject: Re: [PATCH] x86: kvm: reset the bootstrap processor when it gets an INIT Message-ID: <20130311174155.GU31619@redhat.com> References: <513DBF45.9030803@redhat.com> <20130311115144.GG31619@redhat.com> <513DDCC2.9070807@redhat.com> <20130311135441.GN31619@redhat.com> <513DE3C4.5000503@siemens.com> <20130311140503.GO31619@redhat.com> <513DE8C5.3090209@redhat.com> <513DFA01.1040500@siemens.com> <20130311172342.GS31619@redhat.com> <513E158B.80506@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <513E158B.80506@siemens.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2485 Lines: 58 On Mon, Mar 11, 2013 at 06:34:03PM +0100, Jan Kiszka wrote: > On 2013-03-11 18:23, Gleb Natapov wrote: > > On Mon, Mar 11, 2013 at 04:36:33PM +0100, Jan Kiszka wrote: > >> On 2013-03-11 15:23, Paolo Bonzini wrote: > >>> Il 11/03/2013 15:05, Gleb Natapov ha scritto: > >>>> 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. > >>> > >>> Neither can go away. For INIT sent by IPI, 10.4.7 says: > >>> > >>> Only the Pentium and P6 family processors support the INIT-deassert IPI. > >>> An INIT-disassert IPI has no affect on the state of the APIC, other than > >>> to reload the arbitration ID register with the value in the APIC ID > >>> register. > >>> > >>> 18.27.1 also says that "In the local APIC, NMI and INIT (except for INIT > >>> deassert) are always treated as edge triggered interrupts". > >>> > >>> > >>> For INIT#, the ICH9 chipset says that "INIT# is driven low for 16 PCI > >>> clocks" when a soft reset is requested. So we can guess that INIT# is > >>> also edge-triggered. > >> > >> Ah, ok. So, virtually, INIT stays asserted until it can be delivered in > >> form of a reset or a vmexit. > >> > > vmexit clears it? > > It has to. Otherwise, it would hit the host on vmxoff. > Why do you thing this is not happening? Look at [1] page 10 "VMX and INIT blocking". Do you think they were lucky to hit CPU while it was in a root mode? [1] http://www.invisiblethingslab.com/resources/2011/Software%20Attacks%20on%20Intel%20VT-d.pdf -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/