[PATCH] libxl/x86: check return value of SHADOW_OP_SET_ALLOCATION domctl

[Jan Beulich <jbeulich@xxxxxxxx>]

The hypervisor may not have enough memory to satisfy the request.

Requested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Especially if the request was mostly fulfilled, guests may have done
fine despite the failure, so there is a risk of perceived regressions
here. But not checking the error at all was certainly wrong.

--- a/tools/libs/light/libxl_x86.c
+++ b/tools/libs/light/libxl_x86.c
@@ -531,8 +531,18 @@ int libxl__arch_domain_create(libxl__gc
     if (d_config->b_info.type != LIBXL_DOMAIN_TYPE_PV) {
         unsigned long shadow = DIV_ROUNDUP(d_config->b_info.shadow_memkb,
                                            1024);
-        xc_shadow_control(ctx->xch, domid, XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION,
-                          NULL, 0, &shadow, 0, NULL);
+        int rc = xc_shadow_control(ctx->xch, domid,
+                                   XEN_DOMCTL_SHADOW_OP_SET_ALLOCATION,
+                                   NULL, 0, &shadow, 0, NULL);
+
+        if (rc) {
+            LOGED(ERROR, domid,
+                  "Failed to set %s allocation: %d (errno:%d)\n",
+                  libxl_defbool_val(d_config->c_info.hap) ? "HAP" : "shadow",
+                  rc, errno);
+            ret = ERROR_FAIL;
+            goto out;
+        }
     }
 
     if (d_config->c_info.type == LIBXL_DOMAIN_TYPE_PV &&