[List added back, please don't drop it] On 16/05/12 10:30, Anup Patel wrote: > There are difference between Cortex-A9 and Cortex-A15 too. I dont understand then when have you got VExpress-A9 guest working a Cortex-A15 ? Well, KVM/ARM started emulating an A9 indeed, but it doesn't mean this is the right thing, and it should be removed. Just think of how you manage processor errata. Are you going to apply A9 workarounds on an A15? How are you going to handle the A15 errata when your kernel believes this is an A9? > Its your choice to accept it or reject it. I really dont care about KVM ARM. Just had some finding which I thought might interest KVM ARM folks. Your collaboration is very much appreciated. Really. But I believe there are *technical* issues with this approach. > We are able to emulate Realview-PB-A8 and VExpress-A9 guest (UP & SMP) on Xvisor ARM running on Cortex-A15. We will be soon have VExpress-A15 guest too. I do not doubt that for a second. You still may want to consider the above point if you're aiming for reliable operation of the guest. Cheers, M. > --Anup > > On Wed, May 16, 2012 at 2:39 PM, Marc Zyngier <marc.zyngier at arm.com<mailto:marc.zyngier at arm.com>> wrote: > On 16/05/12 08:54, Peter Maydell wrote: >> On 16 May 2012 05:05, Anup Patel <anup at brainfault.org<mailto:anup at brainfault.org>> wrote: >>> Realview-PB-A8 kernel boots fine on QEMU Emulator. The kernel gets alignment >>> faults only when we try to use KVM ARM. >> >> TCG QEMU doesn't emulate alignment faults, so you'll never see them. >> (This is really a bug in TCG QEMU.) >> >>> Although, I did not see this issue with VExpress-A9 kernel, so have >>> mentioned it explicitly in my patch. Making this change CPUID specific would >>> be even more correct way of doing it. >> >> What I mean is that we should be checking CPUID and saying "no, >> you cannot emulate an A8 or A9 with KVM". > > I strongly agree with that. We should certainly push back on anything > that pretends to expose a different CPU than the one we actually run on. > > This is fundamentally broken because we're actually running on the > physical CPU. Think errata workaround, cache behavior, all the subtle > things that make A8/A9 vastly different from A15. > > It you want to emulate an A8, use TCG QEMU. > > M. > -- > Jazz is not dead. It just smells funny... > > > -- Jazz is not dead. It just smells funny...
