x86/platform/UV: Add Support for UV4 Hubless systems

Add recognition and support for UV4 hubless systems.
Signed-off-by: Mike Travis <travis@sgi.com>
Reviewed-by: Russ Anderson <rja@hpe.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Dimitri Sivanich <sivanich@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170125163517.398537358@asylum.americas.sgi.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

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

@@ -10,6 +10,7 @@ struct mm_struct;
 
 extern enum uv_system_type get_uv_system_type(void);
 extern int is_uv_system(void);
+extern int is_uv_hubless(void);
 extern void uv_cpu_init(void);
 extern void uv_nmi_init(void);
 extern void uv_system_init(void);
@@ -23,6 +24,7 @@ extern const struct cpumask *uv_flush_tlb_others(const struct cpumask *cpumask,
 
 static inline enum uv_system_type get_uv_system_type(void) { return UV_NONE; }
 static inline int is_uv_system(void)	{ return 0; }
+static inline int is_uv_hubless(void)	{ return 0; }
 static inline void uv_cpu_init(void)	{ }
 static inline void uv_system_init(void)	{ }
 static inline const struct cpumask *

arch/x86/kernel/apic/x2apic_uv_x.c

@@ -42,6 +42,7 @@
 DEFINE_PER_CPU(int, x2apic_extra_bits);
 
 static enum uv_system_type	uv_system_type;
+static bool			uv_hubless_system;
 static u64			gru_start_paddr, gru_end_paddr;
 static u64			gru_dist_base, gru_first_node_paddr = -1LL, gru_last_node_paddr;
 static u64			gru_dist_lmask, gru_dist_umask;
@@ -225,8 +226,14 @@ static int __init uv_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 	int pnodeid;
 	int uv_apic;
 
-	if (strncmp(oem_id, "SGI", 3) != 0)
+	if (strncmp(oem_id, "SGI", 3) != 0) {
+		if (strncmp(oem_id, "NSGI", 4) == 0) {
+			uv_hubless_system = true;
+			pr_info("UV: OEM IDs %s/%s, HUBLESS\n",
+				oem_id, oem_table_id);
+		}
 		return 0;
+	}
 
 	if (numa_off) {
 		pr_err("UV: NUMA is off, disabling UV support\n");
@@ -300,6 +307,12 @@ int is_uv_system(void)
 }
 EXPORT_SYMBOL_GPL(is_uv_system);
 
+int is_uv_hubless(void)
+{
+	return uv_hubless_system;
+}
+EXPORT_SYMBOL_GPL(is_uv_hubless);
+
 void **__uv_hub_info_list;
 EXPORT_SYMBOL_GPL(__uv_hub_info_list);
 
@@ -1353,7 +1366,7 @@ static void __init build_socket_tables(void)
 	}
 }
 
-void __init uv_system_init(void)
+static void __init uv_system_init_hub(void)
 {
 	struct uv_hub_info_s hub_info = {0};
 	int bytes, cpu, nodeid;
@@ -1490,4 +1503,17 @@ void __init uv_system_init(void)
 		reboot_type = BOOT_ACPI;
 }
 
+/*
+ * There is a small amount of UV specific code needed to initialize a
+ * UV system that does not have a "UV HUB" (referred to as "hubless").
+ */
+void __init uv_system_init(void)
+{
+	if (likely(!is_uv_system() && !is_uv_hubless()))
+		return;
+
+	if (is_uv_system())
+		uv_system_init_hub();
+}
+
 apic_driver(apic_x2apic_uv_x);