x86/platform/uv/BAU: Disable BAU on single hub configurations

The BAU confers no benefit to a UV system running with only one hub/socket.
Permanently disable the BAU driver if there are less than two hubs online
to avoid BAU overhead. We have observed failed boots on single-socket UV4
systems caused by BAU that are avoided with this patch.

Also, while at it, consolidate initialization error blocks and fix a
memory leak.

Signed-off-by: Andrew Banman <abanman@hpe.com>
Acked-by: Russ Anderson <rja@hpe.com>
Acked-by: Mike Travis <mike.travis@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: tony.ernst@hpe.com
Link: http://lkml.kernel.org/r/1500588351-78016-1-git-send-email-abanman@hpe.com
[ Minor cleanups. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 18 insertions, 5 deletions

diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index fd8759111b65..3e4bdb442fbc 100644
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -2221,13 +2221,17 @@ static int __init uv_bau_init(void)
         else if (is_uv1_hub())
                 ops = uv1_bau_ops;
 
+        nuvhubs = uv_num_possible_blades();
+        if (nuvhubs < 2) {
+                pr_crit("UV: BAU disabled - insufficient hub count\n");
+                goto err_bau_disable;
+        }
+
         for_each_possible_cpu(cur_cpu) {
                 mask = &per_cpu(uv_flush_tlb_mask, cur_cpu);
                 zalloc_cpumask_var_node(mask, GFP_KERNEL, cpu_to_node(cur_cpu));
         }
 
-        nuvhubs = uv_num_possible_blades();
-
         uv_base_pnode = 0x7fffffff;
         for (uvhub = 0; uvhub < nuvhubs; uvhub++) {
                 cpus = uv_blade_nr_possible_cpus(uvhub);
@@ -2240,9 +2244,8 @@ static int __init uv_bau_init(void)
                 enable_timeouts();
 
         if (init_per_cpu(nuvhubs, uv_base_pnode)) {
-                set_bau_off();
-                nobau_perm = 1;
-                return 0;
+                pr_crit("UV: BAU disabled - per CPU init failed\n");
+                goto err_bau_disable;
         }
 
         vector = UV_BAU_MESSAGE;
@@ -2268,6 +2271,16 @@ static int __init uv_bau_init(void)
         }
 
         return 0;
+
+err_bau_disable:
+
+        for_each_possible_cpu(cur_cpu)
+                free_cpumask_var(per_cpu(uv_flush_tlb_mask, cur_cpu));
+
+        set_bau_off();
+        nobau_perm = 1;
+
+        return -EINVAL;
 }
 core_initcall(uv_bau_init);
 fs_initcall(uv_ptc_init);