xen/x86: Use ASSERT instead of VIRTUAL_BUG_ON for phys_to_nid

VIRTUAL_BUG_ON is an empty macro used in phys_to_nid. This
results in two lines of error-checking code in phys_to_nid
that is not actually working and causing two compilation
errors:
1. error: "MAX_NUMNODES" undeclared (first use in this function).
   This is because in the common header file, "MAX_NUMNODES" is
   defined after the common header file includes the ARCH header
   file, where phys_to_nid has attempted to use "MAX_NUMNODES".
   This error was resolved after we moved the phys_to_nid from
   x86 ARCH header file to common header file.
2. error: wrong type argument to unary exclamation mark.
   This is because, the error-checking code contains !node_data[nid].
   But node_data is a data structure variable, it's not a pointer.

So, in this patch, we use ASSERT instead of VIRTUAL_BUG_ON to
enable the two lines of error-checking code. And fix the left
compilation errors by replacing !node_data[nid] to
!node_data[nid].node_spanned_pages. Although NUMA allows one node
can only have CPUs but without any memory. And node with 0 bytes
of memory might have an entry in memnodemap[] theoretically. But
that doesn't mean phys_to_nid can find any valid address from a
node with 0 bytes memory.

Signed-off-by: Wei Chen <wei.chen@arm.com>
Tested-by: Jiamei Xie <jiamei.xie@arm.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/include/xen/numa.h

@@ -35,8 +35,6 @@ struct node {
 extern int compute_hash_shift(const struct node *nodes,
                               unsigned int numnodes, const nodeid_t *nodeids);
 
-#define VIRTUAL_BUG_ON(x)
-
 extern bool numa_off;
 
 extern void numa_add_cpu(unsigned int cpu);
@@ -69,9 +67,9 @@ extern struct node_data node_data[];
 static inline nodeid_t __attribute_pure__ phys_to_nid(paddr_t addr)
 {
     nodeid_t nid;
-    VIRTUAL_BUG_ON((paddr_to_pdx(addr) >> memnode_shift) >= memnodemapsize);
+    ASSERT((paddr_to_pdx(addr) >> memnode_shift) < memnodemapsize);
     nid = memnodemap[paddr_to_pdx(addr) >> memnode_shift];
-    VIRTUAL_BUG_ON(nid >= MAX_NUMNODES || !node_data[nid]);
+    ASSERT(nid < MAX_NUMNODES && node_data[nid].node_spanned_pages);
     return nid;
 }