On 25/06/14 15:56, Joel Schopp wrote: > > On 06/24/2014 05:28 PM, Peter Maydell wrote: >> On 24 June 2014 20:28, Joel Schopp <joel.schopp@xxxxxxx> wrote: >>> On 06/19/2014 04:21 AM, Marc Zyngier wrote: >>>> The GIC CPU interface is always 4k aligned. If the host is using >>>> 64k pages, it is critical to place the guest's GICC interface at the >>>> same relative alignment as the host's GICV. Failure to do so results >>>> in an impossibility for the guest to deal with interrupts. >>>> >>>> Add a KVM_DEV_ARM_VGIC_GRP_ADDR_OFFSET attribute for the VGIC, allowing >>>> userspace to retrieve the GICV offset in a page. It becomes then trivial >>>> to adjust the GICC base address for the guest. >>> >>> Does this mean there is a corresponding patch for qemu? >> Not as far as I know. It's a bit awkward on the QEMU end because >> we really want to provide the guest a consistent memory map >> regardless of the host CPU. So at best we'd probably use it to >> say "sorry, can't run on this CPU/host kernel". > I think most arm64 servers are going to run with 64k pages. It seems > like a major problem to have qemu not work on these systems. How many of them will be with the GICC *not* 64kB aligned? >> >> (That said, if you think you can make QEMU usefully use the >> information and want to write a QEMU patch I'm not averse >> to the idea.) > I'll have to think about this approach some more, but I'm not opposed to > doing the work if I thought it was the right thing to do. > >> >> kvmtool is probably better placed to take advantage of it since >> it takes more of a "deal with what the host provides you" >> philosophy. > kvmtool is fun as a play toy, but in the real world nobody is building > clouds using kvmtool, they use kvm with qemu. A play toy? Hmmm. Do you realise that most of KVM on arm64 has been written using this play toy? M. -- Jazz is not dead. It just smells funny... -- 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
