On 24/09/15 13:08, Pavel Fedin wrote: > Hello! > >> The only thing that is pure 64-bit is the MRS/MSR _instruction_ in >> Aarch64, which always takes a x<nn> register. >> So can you model the register size according to the spec and allow >> 32-bit accesses from userland? > > I would like to complete the rework and respin v4, but this is, i guess, the only major issue left. > Additionally, it impacts the API. So... > In order to allow 32-bit accesses we would have to drop using ARM64_SYS_REG() for building > attribute ID and introduce something own, like KVM_DEV_ARM_VGIC_REG(). It will have different bits > layout (actually it will be missing 'arch' and 'size' field, and instead i will use > KVM_DEV_ARM_VGIC_64BIT flag for length specification, the same as for redistributor. > Will this be OK ? No, instead you should go with your original approach ;-) Thinking about that again I see that this interface is of course modeled after the architectured GICv3 system registers, where AArch32 has its own, separate encoding. So it's perfectly fine to use that 64-bit interface between userland and KVM now. If we later get Aarch32 support for the GICv3, we can add the appropriate Aarch32 sysregs to that interface and have a natural match. So: sorry for the noise, you can just go ahead with that native 64-bit sysregs encoding for [SG]ET_ONE_REG as you had before. Cheers, Andre. -- 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
