On Wed, Apr 17, 2013 at 3:35 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > 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... > But we're not talking about disabling the A7's, we're talking about disabling KVM/ARM, a quite new feature, on a system where it's not well-tested and may cause boot problems or other issues that we haven't investigated in depth yet. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
