[PATCH v2 4/9] xen/x86: Use ASSERT instead of VIRTUAL_BUG_ON for phys_to_nid

[Wei Chen <wei.chen@xxxxxxx>]

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@xxxxxxx>
Tested-by: Jiamei Xie <jiamei.xie@xxxxxxx>
---
v1 -> v2:
1. Move from part#1 to part#2. (Comment from NUMA part1 series)
2. Refine the justification of using
   !node_data[nid].node_spanned_pages. (From NUMA part1 series)
3. Use ASSERT to replace VIRTUAL_BUG_ON in phys_to_nid.
4. Adjust the conditional express for ASSERT.
5. Move MAX_NUMNODES from xen/numa.h to asm/numa.h for x86.
6. Use conditional macro to gate MAX_NUMNODES for other architectures.
---
 xen/include/xen/numa.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/xen/include/xen/numa.h b/xen/include/xen/numa.h
index db0e524a0e..695ad51df0 100644
--- a/xen/include/xen/numa.h
+++ b/xen/include/xen/numa.h
@@ -36,8 +36,6 @@ struct node {
 extern int compute_hash_shift(struct node *nodes, int numnodes,
                               nodeid_t *nodeids);
 
-#define VIRTUAL_BUG_ON(x)
-
 /* Enumerations for NUMA status. */
 enum numa_mode {
     numa_on = 0,
@@ -77,9 +75,9 @@ extern struct node_data node_data[];
 static inline __attribute__((pure)) nodeid_t 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;
 }
 
-- 
2.25.1