[Xen-devel] [PATCH v5 1/8] numa: __node_distance() should return u8

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

SLIT values are byte-sized and some of them (0-9 and 255) have
special meaning. Adjust __node_distance() to reflect this and
modify scrub_heap_pages() and do_sysctl() to deal with
__node_distance() returning an invalid SLIT entry.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---

Changes in v5:
* XEN_SYSCTL_numainfo knows about NUMA_NO_DISTANCE
* Cleaner changes in __node_distance()

 xen/arch/x86/srat.c        |   13 ++++++++++---
 xen/common/page_alloc.c    |    4 ++--
 xen/common/sysctl.c        |    6 +++++-
 xen/include/asm-x86/numa.h |    2 +-
 xen/include/xen/numa.h     |    3 ++-
 5 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/srat.c b/xen/arch/x86/srat.c
index dfabba3..92c89a5 100644
--- a/xen/arch/x86/srat.c
+++ b/xen/arch/x86/srat.c
@@ -496,14 +496,21 @@ static unsigned node_to_pxm(nodeid_t n)
        return 0;
 }
 
-int __node_distance(nodeid_t a, nodeid_t b)
+u8 __node_distance(nodeid_t a, nodeid_t b)
 {
-       int index;
+       unsigned index;
+       u8 slit_val;
 
        if (!acpi_slit)
                return a == b ? 10 : 20;
        index = acpi_slit->locality_count * node_to_pxm(a);
-       return acpi_slit->entry[index + node_to_pxm(b)];
+       slit_val = acpi_slit->entry[index + node_to_pxm(b)];
+
+       /* ACPI defines 0xff as an unreachable node and 0-9 are undefined */
+       if ((slit_val == 0xff) || (slit_val <= 9))
+               return NUMA_NO_DISTANCE;
+       else
+               return slit_val;
 }
 
 EXPORT_SYMBOL(__node_distance);
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index d999296..bfb356e 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1434,13 +1434,13 @@ void __init scrub_heap_pages(void)
         /* Figure out which NODE CPUs are close. */
         for_each_online_node ( j )
         {
-            int distance;
+            u8 distance;
 
             if ( cpumask_empty(&node_to_cpumask(j)) )
                 continue;
 
             distance = __node_distance(i, j);
-            if ( distance < last_distance )
+            if ( (distance < last_distance) && (distance != NUMA_NO_DISTANCE) )
             {
                 last_distance = distance;
                 best_node = j;
diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
index 0cb6ee1..6fdd029 100644
--- a/xen/common/sysctl.c
+++ b/xen/common/sysctl.c
@@ -304,7 +304,11 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) 
u_sysctl)
                 {
                     uint32_t distance = ~0u;
                     if ( node_online(i) && node_online(j) )
-                        distance = __node_distance(i, j);
+                    {
+                        u8 d = __node_distance(i, j);
+                        if ( d != NUMA_NO_DISTANCE )
+                            distance = d;
+                    }
                     if ( copy_to_guest_offset(
                         ni->node_to_node_distance,
                         i*(max_node_index+1) + j, &distance, 1) )
diff --git a/xen/include/asm-x86/numa.h b/xen/include/asm-x86/numa.h
index cc5b5d1..7a489d3 100644
--- a/xen/include/asm-x86/numa.h
+++ b/xen/include/asm-x86/numa.h
@@ -85,6 +85,6 @@ extern int valid_numa_range(u64 start, u64 end, nodeid_t 
node);
 #endif
 
 void srat_parse_regions(u64 addr);
-extern int __node_distance(nodeid_t a, nodeid_t b);
+extern u8 __node_distance(nodeid_t a, nodeid_t b);
 
 #endif
diff --git a/xen/include/xen/numa.h b/xen/include/xen/numa.h
index ac4b391..7aef1a8 100644
--- a/xen/include/xen/numa.h
+++ b/xen/include/xen/numa.h
@@ -7,7 +7,8 @@
 #define NODES_SHIFT     0
 #endif
 
-#define NUMA_NO_NODE    0xFF
+#define NUMA_NO_NODE     0xFF
+#define NUMA_NO_DISTANCE 0xFF
 
 #define MAX_NUMNODES    (1 << NODES_SHIFT)
 
-- 
1.7.1


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