This adds basic support for HW assisted debug. The ioctl interface to
KVM allows us to pass an implementation defined number of break and
watch point registers. When KVM_GUESTDBG_USE_HW is specified these
debug registers will be installed in place on the world switch into the
guest.

The hardware is actually capable of more advanced matching but it is
unclear if this expressiveness is available via the gdbstub protocol.
Signed-off-by: NAlex Bennée <alex.bennee@linaro.org>
Message-id: 1449599553-24713-5-git-send-email-alex.bennee@linaro.org
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>