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 kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
