On 17/04/13 11:19, Russell King - ARM Linux wrote: > On Fri, Apr 12, 2013 at 02:49:43PM +0100, Marc Zyngier wrote: >> On 12/04/13 14:40, Peter Maydell wrote: >>> On 12 April 2013 14:24, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: >>>> Nak. The fact that one of the CPUs seem to hang is a sure sign that >>>> something is severely broken, and you definitely want to fix that issue, >>>> instead of blindly ignoring it. >>>> >>>> Additionally, it seems you're just papering over the issue. You should >>>> be able to exclude the A7 processors, but not completely deny KVM from >>>> running on the hardware. >>> >>> Well that might be nice, as would fully supporting big.LITTLE >>> systems. But until somebody actually does that work it seems >>> like a better idea to fail gracefully rather than having a 50% >>> chance of failing gracefully and a 50% chance of going weird. >> >> Nothing prevents the kernel (or even the user) from forcing the affinity >> of the CPU threads to the A15s. I'm not saying we should ignore the >> problem either. Just that the proposed approach is wrong. > > But nothing guarantees that you get that affinity. If you offline all > A15 CPUs, then you will find those threads running on whatever is left. > Affinity is just a hint, nothing more. I completely agree with you. But if we're left with only CPUs we can't run on, we're screwed and must abort. It's the same story as the RealView PB-X, where only one of the two A9 has NEON. If the NEON-capable core is down, any process using NEON is virtually dead. Should that be a reason to completely disable the HW (in this case the 3 A7s)? I'm not sure... M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
