• Ed Swierk's avatar
    KVM: Xen PV-on-HVM guest support · ffde22ac
    Ed Swierk authored
    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: default avatarEd Swierk <eswierk@aristanetworks.com>
    Signed-off-by: default avatarJan Kiszka <jan.kiszka@siemens.com>
    Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
    Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
    ffde22ac
kvm.h 4.89 KB