• Borislav Petkov's avatar
    kvm: Emulate MOVBE · 84cffe49
    Borislav Petkov authored
    This basically came from the need to be able to boot 32-bit Atom SMP
    guests on an AMD host, i.e. a host which doesn't support MOVBE. As a
    matter of fact, qemu has since recently received MOVBE support but we
    cannot share that with kvm emulation and thus we have to do this in the
    host. We're waay faster in kvm anyway. :-)
    So, we piggyback on the #UD path and emulate the MOVBE functionality.
    With it, an 8-core SMP guest boots in under 6 seconds.
    Also, requesting MOVBE emulation needs to happen explicitly to work,
    i.e. qemu -cpu n270,+movbe...
    Just FYI, a fairly straight-forward boot of a MOVBE-enabled 3.9-rc6+
    kernel in kvm executes MOVBE ~60K times.
    Signed-off-by: default avatarAndre Przywara <andre@andrep.de>
    Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>