K 10
svn:author
V 3
jhb
K 8
svn:date
V 27
2018-04-06T22:03:43.377016Z
K 7
svn:log
V 1077
Add a way to temporarily suspend and resume virtual CPUs.

This is used as part of implementing run control in bhyve's debug
server.  The hypervisor now maintains a set of "debugged" CPUs.
Attempting to run a debugged CPU will fail to execute any guest
instructions and will instead report a VM_EXITCODE_DEBUG exit to
the userland hypervisor.  Virtual CPUs are placed into the debugged
state via vm_suspend_cpu() (implemented via a new VM_SUSPEND_CPU ioctl).
Virtual CPUs can be resumed via vm_resume_cpu() (VM_RESUME_CPU ioctl).

The debug server suspends virtual CPUs when it wishes them to stop
executing in the guest (for example, when a debugger attaches to the
server).  The debug server can choose to resume only a subset of CPUs
(for example, when single stepping) or it can choose to resume all
CPUs.  The debug server must explicitly mark a CPU as resumed via
vm_resume_cpu() before the virtual CPU will successfully execute any
guest instructions.

Reviewed by:	avg, grehan
Tested on:	Intel (jhb), AMD (avg)
Differential Revision:	https://reviews.freebsd.org/D14466

END