On Sat, 9 Jan 2016 13:29:56 +0100 Christoffer Dall <christoffer.dall@xxxxxxxxxx> wrote: > On Thu, Jan 07, 2016 at 09:36:47PM +0100, Andrew Jones wrote: > > On Thu, Jan 07, 2016 at 02:56:15PM +0000, Peter Maydell wrote: > > > On 7 January 2016 at 14:49, Shannon Zhao <zhaoshenglong@xxxxxxxxxx> wrote: > > > >>> + > > > >>> +Groups: > > > >>> + KVM_DEV_ARM_PMU_GRP_IRQ > > > >>> + Attributes: > > > >>> + The attr field of kvm_device_attr encodes one value: > > > >>> + bits: | 63 .... 32 | 31 .... 0 | > > > >>> + values: | reserved | vcpu_index | > > > >>> + A value describing the PMU overflow interrupt number for the specified > > > >>> + vcpu_index vcpu. This interrupt could be a PPI or SPI, but for one VM the > > > >>> + interrupt type must be same for each vcpu. As a PPI, the interrupt number is > > > >>> + same for all vcpus, while as a SPI it must be different for each vcpu. > > > >> > > > >> I see we're using vcpu_index rather than MPIDR affinity value > > > >> for specifying which CPU we're configuring. Is this in line with > > > >> our planned API for GICv3 configuration? > > > >> > > > > Here vcpu_index is used to indexing the vCPU, no special use. > > > > > > Yes, but you can identify the CPU by index, or by its MPIDR. > > > We had a discussion about which was the best way for doing > > > the VGIC API, and I can't remember which way round we ended up > > > going for. Whichever we chose, we should do the same thing here. > > > > I think we should start up a new discussion on this. My understanding, > > after a chat with Igor, who was involved in the untangling of vcpu-id and > > apic-id for x86, is that using vcpu-id is preferred, unless of course > > the device expects an apic-id/mpidr, in which case there's no reason to > > translate it on both sides. > > > > I'm fairly strongly convinced that we should use the full 32-bit > compressed MPIDR for everything ARM related going forward, as this will > cover any case required and leverages and architecturally defined way of > uniquely identifying a (v)CPU. +1. vcpu_ids, indexes or any other constructs are just a bunch of KVM-specific definitions that do not describe the VM from an architecture PoV. In contrast, the MPIDR is guaranteed to be unique stable, and identifies a given (v)CPU. As for the PMU: either 1) we instantiate it together with the CPU (with a new capability/feature), or 2) we map it to a MPIDR, and associate it with its vcpu at runtime. I'm slightly in favor of 1), as it simplifies things a bit, but 2) is doable as well (GICv3 has similar requirements). 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
