On Wednesday 30 November 2011, Stefano Stabellini wrote: > On Tue, 29 Nov 2011, Arnd Bergmann wrote: > > On Tuesday 29 November 2011, Stefano Stabellini wrote: > > > > Do you have a pointer to the kernel sources for the Linux guest? > > We have very few changes to the Linux kernel at the moment (only 3 > commits!), just enough to be able to issue hypercalls and start a PV > console. > > A git branch is available here (not ready for submission): > > git://xenbits.xen.org/people/sstabellini/linux-pvhvm.git arm Ok, interesting. There really isn't much of the platform support that I was expecting there. I finally found the information I was looking for in the xen construct_dom0() function: 167 regs->r0 = 0; /* SBZ */ 168 regs->r1 = 2272; /* Machine NR: Versatile Express */ 169 regs->r2 = 0xc0000100; /* ATAGS */ What this means is that you are emulating the current ARM/Keil reference board, at least to the degree that is necessary to get the guest started. This is the same choice people have made for KVM, but it's not necessarily the best option in the long run. In particular, this board has a lot of hardware that you claim to have by putting the machine number there, when you don't really want to emulate it. Pawell Moll is working on a variant of the vexpress code that uses the flattened device tree to describe the present hardware [1], and I think that would be a much better target for an official release. Ideally, the hypervisor should provide the device tree binary (dtb) to the guest OS describing the hardware that is actually there. This would also be the place where you tell the guest that it should look for PV devices. I'm not familiar with how Xen announces PV devices to the guest on other architectures, but you have the choice between providing a full "binding", i.e. a formal specification in device tree format for the guest to detect PV devices in the same way as physical or emulated devices, or just providing a single place in the device tree in which the guest detects the presence of a xen device bus and then uses hcalls to find the devices on that bus. Another topic is the question whether there are any hcalls that we should try to standardize before we get another architecture with multiple conflicting hcall APIs as we have on x86 and powerpc. Arnd [1] http://www.spinics.net/lists/arm-kernel/msg149604.html -- 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
