[Xen-devel] [PATCH RFC 4/6] xen: Print and use errno where applicable.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

In Xen 4.6 commit cd2f100f0f61b3f333d52d1737dd73f02daee592
"libxc: Fix do_memory_op to return negative value on errors"
made the libxc API less odd-ball: On errors, return value is
-1 and error code is in errno. On success the return value
is either 0 or an positive value.

Since we could be running with an old toolstack in which the
Exx value is in rc or the newer, we print both and return
the -EXX depending on rc == -1 condition.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 xen-hvm.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/xen-hvm.c b/xen-hvm.c
index 0408462..a92bc14 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -345,11 +345,12 @@ go_physmap:
         unsigned long idx = pfn + i;
         xen_pfn_t gpfn = start_gpfn + i;
 
+        /* In Xen 4.6 rc is -1 and errno contains the error value. */
         rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, 
idx, gpfn);
         if (rc) {
             DPRINTF("add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
-                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
-            return -rc;
+                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, 
errno);
+            return rc == -1 ? -errno : -rc;
         }
     }
 
@@ -422,11 +423,12 @@ static int xen_remove_from_physmap(XenIOState *state,
         xen_pfn_t idx = start_addr + i;
         xen_pfn_t gpfn = phys_offset + i;
 
+        /* In Xen 4.6 rc is -1 and errno contains the error value. */
         rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, 
idx, gpfn);
         if (rc) {
             fprintf(stderr, "add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
-                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
-            return -rc;
+                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, 
errno);
+            return rc == -1 ? -errno : -rc;
         }
     }
 
-- 
2.1.0


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