Ed Swierk ffde22ac53 KVM: Xen PV-on-HVM guest support ... Support for Xen PV-on-HVM guests can be implemented almost entirely in userspace, except for handling one annoying MSR that maps a Xen hypercall blob into guest address space. A generic mechanism to delegate MSR writes to userspace seems overkill and risks encouraging similar MSR abuse in the future. Thus this patch adds special support for the Xen HVM MSR. I implemented a new ioctl, KVM_XEN_HVM_CONFIG, that lets userspace tell KVM which MSR the guest will write to, as well as the starting address and size of the hypercall blobs (one each for 32-bit and 64-bit) that userspace has loaded from files. When the guest writes to the MSR, KVM copies one page of the blob from userspace to the guest. I've tested this patch with a hacked-up version of Gerd's userspace code, booting a number of guests (CentOS 5.3 i386 and x86_64, and FreeBSD 8.0-RC1 amd64) and exercising PV network and block devices. [jan: fix i386 build warning] [avi: future proof abi with a flags field] Signed-off-by: Ed Swierk <eswierk@aristanetworks.com> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>		2009-12-03 09:32:18 +02:00
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api.txt	KVM: Xen PV-on-HVM guest support	2009-12-03 09:32:18 +02:00