On Wed, Sep 07, 2011 at 07:25:24PM +0300, Avi Kivity wrote: > On 09/07/2011 06:56 PM, Don Zickus wrote: > >> > >> And hope that no other NMI was generated while we're handling this > >> one. It's a little... fragile? > > > >No. If another NMI is generated while we are processing the current one > >it should get latched. Upon completion of the current one, the cpu should > >jump right back into the nmi exception routine again. The only downside > >is when multiple NMIs come in during the processing of the current one. > >Only one can be latched, so the others get dropped. > > Ah, yes, I remember now. > > >But we are addressing > >that. > > > > May I ask how? Detecting a back-to-back NMI? Pretty boring actually. Currently we execute an NMI handler until one of them returns handled. Then we stop. This may cause us to miss an NMI in the case of multiple NMIs at once. Now we are changing it to execute _all_ the handlers to make sure we didn't miss one. But then the downside here is we accidentally handle an NMI that was latched. This would cause a 'Dazed on confused' message as that NMI was already handled by the previous NMI. We are working on an algorithm to detect this condition and flag it (nothing complicated). But it may never be perfect. On the other hand, what else are we going to do with an edge-triggered shared interrupt line? Cheers, Don -- 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
