[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] NMI deferral on i386
>>> Keir Fraser <keir@xxxxxxxxxxxxx> 16.05.07 14:32 >>> >On 16/5/07 11:10, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > >>> It sounds a bit painful. Also it's the exit-to-guest path that is more of a >>> pain to deal with. In this case we may have restored a segment register by >>> the time we take the NMI. What do we do in this case about restoring the >>> segment register safely? Races in updating GDT/LDT may mean that the reload >>> still may fault, even though it didn't just before; also we may need to do >>> work in Xen (e.g., shadow-mode stuff) in interrupts-enabled context to fix >>> up a #GP or #PG. >> >> Indeed. Nevertheless, for non-restartable MCEs, deferral is impossible, and >> hence some mechanism would still be needed (unless we say the machine's >> going down anyway in this case and we don't care about getting a proper >> reason logged). > >You mean, like with a #DF, that sometimes a #MC may have bogus CS:EIP and so >you cannot IRET from it? I'm not sure how much we care about losing these >and turning a possibly-informative crash into an ugly and confusing crash. Yes, that's what I mean. And I'm not so much concerned about turning a (very rare) 'nice' crash into an 'ugly' one, but more about that fact that until the system actually crashes it may continue to execute for a short while, possibly making the data corruption situation worse. >Personally I've never seen a #MC or had one reported to me, restartable or >not. Maybe I'm lucky. :-) I did see quite a few non-restartable ones (on native Linux), and it took me some time to actually get the system into a state where I could see the related messages before it rebooted. I don't have that system anymore, though, otherwise I might be have been able to use it for testing purposes here. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |