x86/platform/uv: Account for UV Hubless in is_uvX_hub Ops

The references in the is_uvX_hub() function uses the hub_info pointer
which will be NULL when the system is hubless.  This change avoids
that NULL dereference.  It is also an optimization in performance.

Signed-off-by: Mike Travis <mike.travis@hpe.com>
Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
Reviewed-by: Dimitri Sivanich <dimitri.sivanich@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Hedi Berriche <hedi.berriche@hpe.com>
Cc: Justin Ernst <justin.ernst@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russ Anderson <russ.anderson@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190910145840.294981941@stormcage.eag.rdlabs.hpecorp.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/uv/uv_hub.h

@@ -19,6 +19,7 @@
 #include <linux/topology.h>
 #include <asm/types.h>
 #include <asm/percpu.h>
+#include <asm/uv/uv.h>
 #include <asm/uv/uv_mmrs.h>
 #include <asm/uv/bios.h>
 #include <asm/irq_vectors.h>
@@ -243,83 +244,61 @@ static inline int uv_hub_info_check(int version)
 #define UV4_HUB_REVISION_BASE		7
 #define UV4A_HUB_REVISION_BASE		8	/* UV4 (fixed) rev 2 */
 
-#ifdef	UV1_HUB_IS_SUPPORTED
+/* WARNING: UVx_HUB_IS_SUPPORTED defines are deprecated and will be removed */
 static inline int is_uv1_hub(void)
 {
-	return uv_hub_info->hub_revision < UV2_HUB_REVISION_BASE;
-}
+#ifdef	UV1_HUB_IS_SUPPORTED
+	return is_uv_hubbed(uv(1));
 #else
-static inline int is_uv1_hub(void)
-{
 	return 0;
-}
 #endif
+}
 
-#ifdef	UV2_HUB_IS_SUPPORTED
 static inline int is_uv2_hub(void)
 {
-	return ((uv_hub_info->hub_revision >= UV2_HUB_REVISION_BASE) &&
-		(uv_hub_info->hub_revision < UV3_HUB_REVISION_BASE));
-}
+#ifdef	UV2_HUB_IS_SUPPORTED
+	return is_uv_hubbed(uv(2));
 #else
-static inline int is_uv2_hub(void)
-{
 	return 0;
-}
 #endif
+}
 
-#ifdef	UV3_HUB_IS_SUPPORTED
 static inline int is_uv3_hub(void)
 {
-	return ((uv_hub_info->hub_revision >= UV3_HUB_REVISION_BASE) &&
-		(uv_hub_info->hub_revision < UV4_HUB_REVISION_BASE));
-}
+#ifdef	UV3_HUB_IS_SUPPORTED
+	return is_uv_hubbed(uv(3));
 #else
-static inline int is_uv3_hub(void)
-{
 	return 0;
-}
 #endif
+}
 
 /* First test "is UV4A", then "is UV4" */
-#ifdef	UV4A_HUB_IS_SUPPORTED
-static inline int is_uv4a_hub(void)
-{
-	return (uv_hub_info->hub_revision >= UV4A_HUB_REVISION_BASE);
-}
-#else
 static inline int is_uv4a_hub(void)
 {
+#ifdef	UV4A_HUB_IS_SUPPORTED
+	if (is_uv_hubbed(uv(4)))
+		return (uv_hub_info->hub_revision == UV4A_HUB_REVISION_BASE);
+#endif
 	return 0;
 }
-#endif
 
-#ifdef	UV4_HUB_IS_SUPPORTED
 static inline int is_uv4_hub(void)
 {
-	return uv_hub_info->hub_revision >= UV4_HUB_REVISION_BASE;
-}
+#ifdef	UV4_HUB_IS_SUPPORTED
+	return is_uv_hubbed(uv(4));
 #else
-static inline int is_uv4_hub(void)
-{
 	return 0;
-}
 #endif
+}
 
 static inline int is_uvx_hub(void)
 {
-	if (uv_hub_info->hub_revision >= UV2_HUB_REVISION_BASE)
-		return uv_hub_info->hub_revision;
-
-	return 0;
+	return (is_uv_hubbed(-2) >= uv(2));
 }
 
 static inline int is_uv_hub(void)
 {
-#ifdef	UV1_HUB_IS_SUPPORTED
-	return uv_hub_info->hub_revision;
-#endif
-	return is_uvx_hub();
+	return is_uv1_hub() || is_uvx_hub();
 }
 
 union uvh_apicid {