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, 15 insertions, 22 deletions

diff --git a/lib/libvmmapi/vmmapi.c b/lib/libvmmapi/vmmapi.c
index bca1174..5660f3b 100644
--- a/lib/libvmmapi/vmmapi.c
+++ b/lib/libvmmapi/vmmapi.c
@@ -368,14 +368,13 @@ vm_get_register(struct vmctx *ctx, int vcpu, int reg, uint64_t *ret_val)
 }
 
 int
-vm_run(struct vmctx *ctx, int vcpu, uint64_t rip, struct vm_exit *vmexit)
+vm_run(struct vmctx *ctx, int vcpu, struct vm_exit *vmexit)
 {
 	int error;
 	struct vm_run vmrun;
 
 	bzero(&vmrun, sizeof(vmrun));
 	vmrun.cpuid = vcpu;
-	vmrun.rip = rip;
 
 	error = ioctl(ctx->fd, VM_RUN, &vmrun);
 	bcopy(&vmrun.vm_exit, vmexit, sizeof(struct vm_exit));
@@ -399,36 +398,22 @@ vm_reinit(struct vmctx *ctx)
 	return (ioctl(ctx->fd, VM_REINIT, 0));
 }
 
-static int
-vm_inject_exception_real(struct vmctx *ctx, int vcpu, int vector,
-    int error_code, int error_code_valid)
+int
+vm_inject_exception(struct vmctx *ctx, int vcpu, int vector, int errcode_valid,
+    uint32_t errcode, int restart_instruction)
 {
 	struct vm_exception exc;
 
-	bzero(&exc, sizeof(exc));
 	exc.cpuid = vcpu;
 	exc.vector = vector;
-	exc.error_code = error_code;
-	exc.error_code_valid = error_code_valid;
+	exc.error_code = errcode;
+	exc.error_code_valid = errcode_valid;
+	exc.restart_instruction = restart_instruction;
 
 	return (ioctl(ctx->fd, VM_INJECT_EXCEPTION, &exc));
 }
 
 int
-vm_inject_exception(struct vmctx *ctx, int vcpu, int vector)
-{
-
-	return (vm_inject_exception_real(ctx, vcpu, vector, 0, 0));
-}
-
-int
-vm_inject_exception2(struct vmctx *ctx, int vcpu, int vector, int errcode)
-{
-
-	return (vm_inject_exception_real(ctx, vcpu, vector, errcode, 1));
-}
-
-int
 vm_apicid2vcpu(struct vmctx *ctx, int apicid)
 {
 	/*
@@ -1198,3 +1183,11 @@ vm_rtc_gettime(struct vmctx *ctx, time_t *secs)
 		*secs = rtctime.secs;
 	return (error);
 }
+
+int
+vm_restart_instruction(void *arg, int vcpu)
+{
+	struct vmctx *ctx = arg;
+
+	return (ioctl(ctx->fd, VM_RESTART_INSTRUCTION, &vcpu));
+}