On Wed, 2011-11-30 at 18:32 +0000, Stefano Stabellini wrote: > On Wed, 30 Nov 2011, Arnd Bergmann wrote: > > > KVM and Xen at least both fall into the single-return-value category, > > so we should be able to agree on a calling conventions. KVM does not > > have an hcall API on ARM yet, and I see no reason not to use the > > same implementation that you have in the Xen guest. > > > > Stefano, can you split out the generic parts of your asm/xen/hypercall.h > > file into a common asm/hypercall.h and submit it for review to the > > arm kernel list? > > Sure, I can do that. > Usually the hypercall calling convention is very hypervisor specific, > but if it turns out that we have the same requirements I happy to design > a common interface. I expect the only real decision to be made is hypercall page vs. raw hvc instruction. The page was useful on x86 where there is a variety of instructions which could be used (at least for PV there was systenter/syscall/int, I think vmcall instruction differs between AMD and Intel also) and gives some additional flexibility. It's hard to predict but I don't think I'd expect that to be necessary on ARM. Another reason for having a hypercall page instead of a raw instruction might be wanting to support 32 bit guests (from ~today) on a 64 bit hypervisor in the future and perhaps needing to do some shimming/arg translation. It would be better to aim for having the interface just be 32/64 agnostic but mistakes do happen. Ian. -- 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
