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Add a way to temporarily suspend and resume virtual CPUs.

Description

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

Details

Committed
jhbApr 6 2018, 10:03 PM
Reviewer
avg
Differential Revision
D14466: Add a way to temporarily suspend and resume virtual CPUs.
Parents
rS332156: MFC r330970, r331067, r331767, r331852, r331858
Branches
Unknown
Tags
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