Simplify instruction restart logic in bhyve.

Keep track of the next instruction to be executed by the vcpu as 'nextrip'.
As a result the VM_RUN ioctl no longer takes the %rip where a vcpu should
start execution.

Also, instruction restart happens implicitly via 'vm_inject_exception()' or
explicitly via 'vm_restart_instruction()'. The APIs behave identically in
both kernel and userspace contexts. The main beneficiary is the instruction
emulation code that executes in both contexts.

bhyve(8) VM exit handlers now treat 'vmexit->rip' and 'vmexit->inst_length'
as readonly:
- Restarting an instruction is now done by calling 'vm_restart_instruction()'
  as opposed to setting 'vmexit->inst_length' to 0 (e.g. emulate_inout())
- Resuming vcpu at an arbitrary %rip is now done by setting VM_REG_GUEST_RIP
  as opposed to changing 'vmexit->rip' (e.g. vmexit_task_switch())

Differential Revision:	https://reviews.freebsd.org/D1526
Reviewed by:		grehan
MFC after:		2 weeks

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/amd64/vmm/intel/vmx.c b/sys/amd64/vmm/intel/vmx.c
index a10a591..c83a8b2 100644
--- a/sys/amd64/vmm/intel/vmx.c
+++ b/sys/amd64/vmm/intel/vmx.c
@@ -2412,6 +2412,7 @@ vmx_exit_process(struct vmx *vmx, int vcpu, struct vm_exit *vmexit)
 		if (vm_mem_allocated(vmx->vm, gpa) ||
 		    apic_access_fault(vmx, vcpu, gpa)) {
 			vmexit->exitcode = VM_EXITCODE_PAGING;
+			vmexit->inst_length = 0;
 			vmexit->u.paging.gpa = gpa;
 			vmexit->u.paging.fault_type = ept_fault_type(qual);
 			vmm_stat_incr(vmx->vm, vcpu, VMEXIT_NESTED_FAULT, 1);