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Support for Xen guests by supporting the Xen hypercalls. This was added to KVM proper to support Amazon's proprietary vmm running ancient AMIs on newer systems
by monocasa 4y ago
Support for Xen guests by supporting the Xen hypercalls. This was added to KVM proper to support Amazon's proprietary vmm running ancient AMIs on newer systems but it seems it's finally getting qemu support too.
- gwd 4y agoI haven't looked at this work in detail, but you need more than just hypercalls to run those ancient guests; those guests are expecting to see xenstore, disk and block backends, and so on. Those would be a lot harder to emulate in the kernel (and probably a bad idea to try anyway).
- monocasa 4y agoI mean, sure, this specific work is in qemu, not the kernel. Some hypercalls are trapped by the kernel, some trap out to a vmm like qemu. Support for pv devices mainly lives in the vmm. But A) even the hypercalls the kernel handles needs to be manually enabled by the vmm, and B) the pv device support ultimately is exposed as in guest memory tables and hypercalls (now partially emulated by qemu).