On 10 May 2016 at 15:04, Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote: > On Fri, May 06, 2016 at 11:45:32AM +0100, Andre Przywara wrote: >> + /* >> + * Currently all guest IRQs are Group1, as Group0 would result >> + * in a FIQ in the guest, which it wouldn't expect. > > I still don't like or understand this comment. This should simply say > that we're making a gross assumption about all interrupts being group1 > here. It's not really an assumption so much as it's a missing feature (aka bug): there's no reason the vGIC shouldn't support group 0 interrupts. We just get away with only supporting group 1 because Linux guests happen to only use group 1 interrupts. If/when the vGIC gains support for group0 interrupts, then it should reset with interrupts configured in group0 by default. >> + * Eventually we want to make this configurable, so we may >> + * revisit this in the future. >> + */ The only reason to make it configurable is to work around a guest kernel bug whereby Linux assumes that all interrupts start out in Group1. Marc sent out a patch earlier today that fixes that bug: https://lkml.org/lkml/2016/5/10/297 Depending on how long it takes you to fix this missing vgic feature, such kernels may all be long-forgotten, in which case you can get away without the config option :-) thanks -- PMM -- 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
