kvm: do not use negative error coded for errno-based errors

Errors derived from sysem errors delivered via -1 return code/errno
should use positive error codes, not negative, in order for them to be
recognized by other components. I.e. we should use
errno::Error::new(EINVAL) and not -EINVAL.

TEST=cargo test --features plugin; cargo test -p kvm
BUG=None

Change-Id: Ibe91745c36765c64aeab2f6aae5cd0ca8f243a42
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/939868
Reviewed-by: Zach Reizner <zachr@chromium.org>

kvm/src/lib.rs

@@ -299,7 +299,7 @@ impl Vm {
                 self.mem_slot_gaps.push(-(slot as i32));
                 Ok(entry.remove())
             }
-            _ => Err(Error::new(-ENOENT))
+            _ => Err(Error::new(ENOENT))
         }
     }
 
@@ -314,7 +314,7 @@ impl Vm {
             Some(mmap) => {
                 // Ensures that there are as many bytes in dirty_log as there are pages in the mmap.
                 if dirty_log_bitmap_size(mmap.size()) > dirty_log.len() {
-                    return Err(Error::new(-EINVAL));
+                    return Err(Error::new(EINVAL));
                 }
                 let mut dirty_log_kvm = kvm_dirty_log {
                     slot,
@@ -327,7 +327,7 @@ impl Vm {
                 let ret = unsafe { ioctl_with_ref(self, KVM_GET_DIRTY_LOG(), &dirty_log_kvm) };
                 if ret == 0 { Ok(()) } else { errno_result() }
             }
-            _ => Err(Error::new(-ENOENT)),
+            _ => Err(Error::new(ENOENT)),
         }
     }