Hi Alex, On Fri, May 15, 2015 at 03:27:13PM +0100, Alex Bennée wrote: > This adds support for userspace to control the HW debug registers for > guest debug. In the debug ioctl we copy the IMPDEF defined number of > registers into a new register set called host_debug_state. There is now > a new vcpu parameter called debug_ptr which selects which register set > is to copied into the real registers when world switch occurs. > > I've moved some helper functions into the hw_breakpoint.h header for > re-use. > > As with single step we need to tweak the guest registers to enable the > exceptions so we need to save and restore those bits. > > Two new capabilities have been added to the KVM_EXTENSION ioctl to allow > userspace to query the number of hardware break and watch points > available on the host hardware. There's the unfortunate possibility that these could vary across cores in a big.LITTLE system (though we haven't seen that thus far). The kernel sanity checks should currently explode if such a case is encountered, but I don't know what we'd do were that to happen. This gets more fun when you consider the context-aware breakpoints are the highest numbered. So the set of (context-aware) breakpoints might not intersect across all CPUs. I'm not sure what the best thing to do is w.r.t. exposing that to userspace. Thanks, Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
