don't expose -errno in public API (#327)

Regardless of what we do internally, most of our API uses standard mechanisms
for reporting errors. Fix vfu_run_ctx() to do so properly as well, and fix a
couple of other references for user-provided callbacks.

This will require a small fix to SPDK.

Signed-off-by: John Levon <john.levon@nutanix.com>
Reviewed-by: Swapnil Ingle <swapnil.ingle@nutanix.com>

2 files changed, 8 insertions, 2 deletions

diff --git a/lib/libvfio-user.c b/lib/libvfio-user.c
index fc427f5..e25787d 100644
--- a/lib/libvfio-user.c
+++ b/lib/libvfio-user.c
@@ -1057,9 +1057,9 @@ vfu_run_ctx(vfu_ctx_t *vfu_ctx)
     blocking = !(vfu_ctx->flags & LIBVFIO_USER_FLAG_ATTACH_NB);
     do {
         err = process_request(vfu_ctx);
-    } while (err >= 0 && blocking);
+    } while (err == 0 && blocking);
 
-    return err >= 0 ? 0 : err;
+    return err == 0 ? 0 : ERROR_INT(-err);
 }
 
 static void
diff --git a/lib/migration.c b/lib/migration.c
index 0e1b2a6..ec07961 100644
--- a/lib/migration.c
+++ b/lib/migration.c
@@ -528,6 +528,9 @@ migration_region_access(vfu_ctx_t *vfu_ctx, char *buf, size_t count,
         pos -= migr->data_offset;
         if (is_write) {
             ret = migr->callbacks.write_data(vfu_ctx, buf, count, pos);
+            if (ret == -1) {
+                ret = -errno;
+            }
         } else {
             /*
              * FIXME <linux/vfio.h> says:
@@ -538,6 +541,9 @@ migration_region_access(vfu_ctx_t *vfu_ctx, char *buf, size_t count,
              * Does this mean that partial reads are not allowed?
              */
             ret = migr->callbacks.read_data(vfu_ctx, buf, count, pos);
+            if (ret == -1) {
+                ret = -errno;
+            }
         }
     }