libxc: Check xc_maximum_ram_page for negative return values.

Instead of assuming everything is always OK. As such
we return now the return value (or zero for success).
The max_mfn is now passed in as the parameter.

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

tools/libxc/include/xenctrl.h

@@ -1509,7 +1509,7 @@ int xc_mmuext_op(xc_interface *xch, struct mmuext_op *op, unsigned int nr_ops,
                  domid_t dom);
 
 /* System wide memory properties */
-long xc_maximum_ram_page(xc_interface *xch);
+int xc_maximum_ram_page(xc_interface *xch, unsigned long *max_mfn);
 
 /* Get current total pages allocated to a domain. */
 long xc_get_tot_pages(xc_interface *xch, uint32_t domid);

tools/libxc/xc_offline_page.c

@@ -412,7 +412,7 @@ int xc_exchange_page(xc_interface *xch, int domid, xen_pfn_t mfn)
     uint32_t status;
     xen_pfn_t new_mfn, gpfn;
     xen_pfn_t *m2p_table;
-    int max_mfn;
+    unsigned long max_mfn;
 
     if ( xc_domain_getinfo(xch, domid, 1, &info) != 1 )
     {
@@ -433,8 +433,8 @@ int xc_exchange_page(xc_interface *xch, int domid, xen_pfn_t mfn)
     }
 
     /* Map M2P and obtain gpfn */
-    max_mfn = xc_maximum_ram_page(xch);
-    if ( !(m2p_table = xc_map_m2p(xch, max_mfn, PROT_READ, NULL)) )
+    rc = xc_maximum_ram_page(xch, &max_mfn);
+    if ( rc || !(m2p_table = xc_map_m2p(xch, max_mfn, PROT_READ, NULL)) )
     {
         PERROR("Failed to map live M2P table");
         return -1;

tools/libxc/xc_private.c

@@ -535,9 +535,16 @@ int do_memory_op(xc_interface *xch, int cmd, void *arg, size_t len)
     return ret;
 }
 
-long xc_maximum_ram_page(xc_interface *xch)
+int xc_maximum_ram_page(xc_interface *xch, unsigned long *max_mfn)
 {
-    return do_memory_op(xch, XENMEM_maximum_ram_page, NULL, 0);
+    long rc = do_memory_op(xch, XENMEM_maximum_ram_page, NULL, 0);
+
+    if ( rc >= 0 )
+    {
+        *max_mfn = rc;
+        rc = 0;
+    }
+    return rc;
 }
 
 long long xc_domain_get_cpu_usage( xc_interface *xch, domid_t domid, int vcpu )

tools/libxc/xg_save_restore.h

@@ -311,7 +311,8 @@ static inline int get_platform_info(xc_interface *xch, uint32_t dom,
     if (xc_version(xch, XENVER_capabilities, &xen_caps) != 0)
         return 0;
 
-    *max_mfn = xc_maximum_ram_page(xch);
+    if (xc_maximum_ram_page(xch, max_mfn))
+        return 0;
 
     *hvirt_start = xen_params.virt_start;
 

tools/misc/xen-mfndump.c

@@ -31,7 +31,7 @@ int help_func(int argc, char *argv[])
 int dump_m2p_func(int argc, char *argv[])
 {
     unsigned long i;
-    long max_mfn;
+    unsigned long max_mfn;
     xen_pfn_t *m2p_table;
 
     if ( argc > 0 )
@@ -41,8 +41,7 @@ int dump_m2p_func(int argc, char *argv[])
     }
 
     /* Map M2P and obtain gpfn */
-    max_mfn = xc_maximum_ram_page(xch);
-    if ( max_mfn < 0 )
+    if ( xc_maximum_ram_page(xch, &max_mfn) < 0 );
     {
         ERROR("Failed to get the maximum mfn");
         return -1;
@@ -183,8 +182,8 @@ int dump_ptes_func(int argc, char *argv[])
     }
 
     /* Map M2P and obtain gpfn */
-    max_mfn = xc_maximum_ram_page(xch);
-    if ( (mfn > max_mfn) ||
+    rc = xc_maximum_ram_page(xch, &max_mfn);
+    if ( rc || (mfn > max_mfn) ||
          !(m2p_table = xc_map_m2p(xch, max_mfn, PROT_READ, NULL)) )
     {
         xc_unmap_domain_meminfo(xch, &minfo);