Deprecate the 3-way return values from vm_gla2gpa() and vm_copy_setup().

Prior to this change both functions returned 0 for success, -1 for failure
and +1 to indicate that an exception was injected into the guest.

The numerical value of ERESTART also happens to be -1 so when these functions
returned -1 it had to be translated to a positive errno value to prevent the
VM_RUN ioctl from being inadvertently restarted. This made it easy to introduce
bugs when writing emulation code.

Fix this by adding an 'int *guest_fault' parameter and setting it to '1' if
an exception was delivered to the guest. The return value is 0 or EFAULT so
no additional translation is needed.

Reviewed by:	tychon
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D2428

1 files changed, 7 insertions, 5 deletions

diff --git a/sys/amd64/include/vmm_instruction_emul.h b/sys/amd64/include/vmm_instruction_emul.h
index 651b3b3..5e7127f 100644
--- a/sys/amd64/include/vmm_instruction_emul.h
+++ b/sys/amd64/include/vmm_instruction_emul.h
@@ -81,17 +81,19 @@ int vie_calculate_gla(enum vm_cpu_mode cpu_mode, enum vm_reg_name seg,
  */
 int vmm_fetch_instruction(struct vm *vm, int cpuid,
 			  struct vm_guest_paging *guest_paging,
-			  uint64_t rip, int inst_length, struct vie *vie);
+			  uint64_t rip, int inst_length, struct vie *vie,
+			  int *is_fault);
 
 /*
  * Translate the guest linear address 'gla' to a guest physical address.
  *
- * Returns 0 on success and '*gpa' contains the result of the translation.
- * Returns 1 if an exception was injected into the guest.
- * Returns -1 otherwise.
+ * retval	is_fault	Interpretation
+ *   0		   0		'gpa' contains result of the translation
+ *   0		   1		An exception was injected into the guest
+ * EFAULT	  N/A		An unrecoverable hypervisor error occurred
  */
 int vm_gla2gpa(struct vm *vm, int vcpuid, struct vm_guest_paging *paging,
-    uint64_t gla, int prot, uint64_t *gpa);
+    uint64_t gla, int prot, uint64_t *gpa, int *is_fault);
 
 void vie_init(struct vie *vie, const char *inst_bytes, int inst_length);