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, 8 insertions, 3 deletions

diff --git a/lib/libvmmapi/vmmapi.h b/lib/libvmmapi/vmmapi.h
index d001cd8..d3ecdc4 100644
--- a/lib/libvmmapi/vmmapi.h
+++ b/lib/libvmmapi/vmmapi.h
@@ -64,7 +64,7 @@ int	vm_setup_memory(struct vmctx *ctx, size_t len, enum vm_mmap_style s);
 void	*vm_map_gpa(struct vmctx *ctx, vm_paddr_t gaddr, size_t len);
 int	vm_get_gpa_pmap(struct vmctx *, uint64_t gpa, uint64_t *pte, int *num);
 int	vm_gla2gpa(struct vmctx *, int vcpuid, struct vm_guest_paging *paging,
-		   uint64_t gla, int prot, uint64_t *gpa);
+		   uint64_t gla, int prot, uint64_t *gpa, int *fault);
 uint32_t vm_get_lowmem_limit(struct vmctx *ctx);
 void	vm_set_lowmem_limit(struct vmctx *ctx, uint32_t limit);
 void	vm_set_memflags(struct vmctx *ctx, int flags);
@@ -131,10 +131,15 @@ int	vm_get_hpet_capabilities(struct vmctx *ctx, uint32_t *capabilities);
 /*
  * Translate the GLA range [gla,gla+len) into GPA segments in 'iov'.
  * The 'iovcnt' should be big enough to accomodate all GPA segments.
- * Returns 0 on success, 1 on a guest fault condition and -1 otherwise.
+ *
+ * retval	fault		Interpretation
+ *   0		  0		Success
+ *   0		  1		An exception was injected into the guest
+ * EFAULT	 N/A		Error
  */
 int	vm_copy_setup(struct vmctx *ctx, int vcpu, struct vm_guest_paging *pg,
-	    uint64_t gla, size_t len, int prot, struct iovec *iov, int iovcnt);
+	    uint64_t gla, size_t len, int prot, struct iovec *iov, int iovcnt,
+	    int *fault);
 void	vm_copyin(struct vmctx *ctx, int vcpu, struct iovec *guest_iov,
 	    void *host_dst, size_t len);
 void	vm_copyout(struct vmctx *ctx, int vcpu, const void *host_src,