On 09/19/2011 06:22 PM, Marcelo Tosatti wrote:
On Mon, Sep 19, 2011 at 06:09:39PM +0300, Avi Kivity wrote: > On 09/19/2011 05:54 PM, Marcelo Tosatti wrote: > >On Mon, Sep 19, 2011 at 05:30:27PM +0300, Avi Kivity wrote: > >> On 09/19/2011 04:54 PM, Marcelo Tosatti wrote: > >> >> >> > >> >> >> Yes, due to NMI-blocked-by-STI. A really touchy area. > >> >> >And we don't need the window exit notification then? I don't understand > >> >> >what nmi_in_progress is supposed to do here. > >> >> > >> >> We need the window notification in both cases. If we're recovering > >> >> from STI, then we don't need to collapse NMIs. If we're completing > >> >> an NMI handler, then we do need to collapse NMIs (since the queue > >> >> length is two, and we just completed one). > >> > > >> >I don't understand what is the point with nmi_in_progress, and the above > >> >hunk, either. Can't inject_nmi do: > >> > > >> >if (nmi_injected + atomic_read(nmi_pending)< 2) > >> > atomic_inc(nmi_pending) > >> > > >> >Instead of collapsing somewhere else? > >> > >> We could. It's not atomic though - two threads executing in > >> parallel could raise the value to three. Could do a cmpxchg loop > >> does an increment bounded to two. I guess this is a lot clearer, > >> thanks. > >> > >> >You'd also have to change > >> >nmi_injected handling in arch code so its value is not "hidden", in > >> >complete_interrupts(). > >> > >> Or maybe make raising nmi_injected not decrement nmi_pending. So: > >> > >> nmi_pending: total number of interrupts in queue > >> nmi_injected: of these, how many are currently being injected > >> > >> yes? > > > >Yes, at the expense of decrementing on subarch code (which is fine, > >apparently). > > > > Hm, we have no place to decrement. Decrement when setting nmi_injected = false, increment when setting nmi_injected = true, in vmx/svm.c.
That gives a queue length of 3: one running nmi and nmi_pending = 2.
> We need to do that when IRET > executes, but we don't want to request an NMI window exit in the > common case of nmi_pending = 1. Do not enable nmi window if nmi_injected = true?
We have to, since we need a back-to-back nmi if the queue length > 1 (including the running nmi).
-- error compiling committee.c: too many arguments to function -- 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
