libxc: Check xc_domain_maximum_gpfn for negative return values

Instead of assuming everything is always OK. We stash
the gpfns value as an parameter. Since we use it in three
of places we might as well update xc_domain_maximum_gpfn
to do the right thing.

Suggested-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

tools/libxc/include/xenctrl.h

@@ -1315,7 +1315,7 @@ int xc_domain_get_tsc_info(xc_interface *xch,
 
 int xc_domain_disable_migrate(xc_interface *xch, uint32_t domid);
 
-int xc_domain_maximum_gpfn(xc_interface *xch, domid_t domid);
+int xc_domain_maximum_gpfn(xc_interface *xch, domid_t domid, xen_pfn_t *gpfns);
 
 int xc_domain_increase_reservation(xc_interface *xch,
                                    uint32_t domid,

tools/libxc/xc_core_arm.c

@@ -30,12 +30,6 @@ xc_core_arch_gpfn_may_present(struct xc_core_arch_context *arch_ctxt,
     return 0;
 }
 
-
-static int nr_gpfns(xc_interface *xch, domid_t domid)
-{
-    return xc_domain_maximum_gpfn(xch, domid) + 1;
-}
-
 int
 xc_core_arch_auto_translated_physmap(const xc_dominfo_t *info)
 {
@@ -48,9 +42,12 @@ xc_core_arch_memory_map_get(xc_interface *xch, struct xc_core_arch_context *unus
                             xc_core_memory_map_t **mapp,
                             unsigned int *nr_entries)
 {
-    unsigned long p2m_size = nr_gpfns(xch, info->domid);
+    xen_pfn_t p2m_size = 0;
     xc_core_memory_map_t *map;
 
+    if ( xc_domain_maximum_gpfn(xch, info->domid, &p2m_size) < 0 )
+        return -1;
+
     map = malloc(sizeof(*map));
     if ( map == NULL )
     {

tools/libxc/xc_core_x86.c

@@ -35,12 +35,6 @@ xc_core_arch_gpfn_may_present(struct xc_core_arch_context *arch_ctxt,
     return 1;
 }
 
-
-static int nr_gpfns(xc_interface *xch, domid_t domid)
-{
-    return xc_domain_maximum_gpfn(xch, domid) + 1;
-}
-
 int
 xc_core_arch_auto_translated_physmap(const xc_dominfo_t *info)
 {
@@ -53,9 +47,12 @@ xc_core_arch_memory_map_get(xc_interface *xch, struct xc_core_arch_context *unus
                             xc_core_memory_map_t **mapp,
                             unsigned int *nr_entries)
 {
-    unsigned long p2m_size = nr_gpfns(xch, info->domid);
+    xen_pfn_t p2m_size = 0;
     xc_core_memory_map_t *map;
 
+    if ( xc_domain_maximum_gpfn(xch, info->domid, &p2m_size) < 0 )
+        return -1;
+
     map = malloc(sizeof(*map));
     if ( map == NULL )
     {
@@ -88,7 +85,12 @@ xc_core_arch_map_p2m_rw(xc_interface *xch, struct domain_info_context *dinfo, xc
     int err;
     int i;
 
-    dinfo->p2m_size = nr_gpfns(xch, info->domid);
+    if ( xc_domain_maximum_gpfn(xch, info->domid, &dinfo->p2m_size) < 0 )
+    {
+        ERROR("Could not get maximum GPFN!");
+        goto out;
+    }
+
     if ( dinfo->p2m_size < info->nr_pages  )
     {
         ERROR("p2m_size < nr_pages -1 (%lx < %lx", dinfo->p2m_size, info->nr_pages - 1);
@@ -210,16 +212,7 @@ int
 xc_core_arch_get_scratch_gpfn(xc_interface *xch, domid_t domid,
                               xen_pfn_t *gpfn)
 {
-    int rc;
-
-    rc = xc_domain_maximum_gpfn(xch, domid);
-
-    if ( rc < 0 )
-        return rc;
-
-    *gpfn = (xen_pfn_t)rc + 1;
-
-    return 0;
+    return xc_domain_maximum_gpfn(xch, domid, gpfn);
 }
 
 /*

tools/libxc/xc_domain.c

@@ -789,9 +789,16 @@ int xc_domain_get_tsc_info(xc_interface *xch,
 }
 
 
-int xc_domain_maximum_gpfn(xc_interface *xch, domid_t domid)
+int xc_domain_maximum_gpfn(xc_interface *xch, domid_t domid, xen_pfn_t *gpfns)
 {
-    return do_memory_op(xch, XENMEM_maximum_gpfn, &domid, sizeof(domid));
+    int rc = do_memory_op(xch, XENMEM_maximum_gpfn, &domid, sizeof(domid));
+
+    if ( rc >= 0 )
+    {
+        *gpfns = rc + 1;
+        rc = 0;
+    }
+    return rc;
 }
 
 int xc_domain_increase_reservation(xc_interface *xch,

tools/libxc/xc_domain_save.c

@@ -939,7 +939,11 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
     }
 
     /* Get the size of the P2M table */
-    dinfo->p2m_size = xc_domain_maximum_gpfn(xch, dom) + 1;
+    if ( xc_domain_maximum_gpfn(xch, dom, &dinfo->p2m_size) < 0 )
+    {
+        ERROR("Could not get maximum GPFN!");
+        goto out;
+    }
 
     if ( dinfo->p2m_size > ~XEN_DOMCTL_PFINFO_LTAB_MASK )
     {