Am 09.08.2013 09:35, schrieb Rusty Russell: > Andreas Färber <afaer...@suse.de> writes: >> [...] If we name it >> cpu_get_byteswap() as proposed by you, then its first argument should be >> a CPUState *cpu. Its value would be read from the derived type's state, >> such as the MSR bit in the code path that you wanted duplicated. The >> function implementing that register-reading would be a hook in CPUClass, >> with a default implementation in qom/cpu.c rather than a fallback in >> stubs/. To access CPUClass, CPUState cannot be NULL, as brought up by >> Stefano for cpu_do_unassigned_access(); not following that pattern >> prevents mixing CPU architectures, which my large refactorings have >> partially been about. Cf. my guest-memory-dump refactoring. >> >> If it is just some random global value, then please don't call it >> cpu_*(). Since sPAPR is not a target of its own, I don't see how/where >> you want to implement that hcall query as per-target function either, >> that might rather call for a QEMUMachine hook? >> >> I don't care or argue about byte lanes here, I am just trying to keep >> API design consistent and not regressing on the way to heterogeneous >> emulation. > > That's a lot of replumbing and indirect function calls for a fairly > obscure case.
It's how QOM methods generally work. And yes, little endian ppc64 is in fact a pretty obscure case. But IBM was just recently reported to adopt the IP licensing model like ARM, so chances are we will see the same mixed-core scenarios as with ARM + MicroBlaze/SuperH these days. http://news.techeye.net/chips/ibms-launches-intel-server-challenge Generally the problem is that we can't have multiple same-named global functions when combining multiple targets, so we need a way to dispatch - either from the individual CPU or from the machine. I would assume in practice mixed cores will have the same endianness. Or by making endianness a user-tweakable property of the virtio devices rather than trying to auto-detect it. > We certainly don't have a nice CPUState lying around in > virtio at the moment, for example. Compare http://git.qemu.org/?p=qemu.git;a=commit;h=c658b94f6e8c206c59d02aa6fbac285b86b53d2c cpu_single_env has since been renamed to the mentioned current_cpu and been changed to CPUState type. > I can try to plumb this in if there's consensus, but I suspect it's > making the job 10x harder. I doubt it's that complicated, estimated less than ten minutes for me, and not doing it is making the other job significantly harder. cpu_get_dump_info() is already a hard nut to crack. Regards, Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
