linux-kernel - [PATCH] Print also the BSP number when announcing cpu

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Date: Mon, 11 Mar 2024 12:39:07 +0800
From: Dashi Cao <dscao999@...mail.com>
To: linux-kernel@...r.kernel.org
Subject: [PATCH] Print also the BSP number when announcing cpu

When announcing CPU, the BSP is always printed as blanks.
This patch will print out the BSP number. It has the assumption
that the BSP is not the last CPU in a CPU node.

Dashi Cao

Signed-off-by: Dashi Cao <dscao999@...mail.com>
---
 arch/x86/kernel/smpboot.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 3f57ce68a3f1..073472742be4 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -931,9 +931,9 @@ static int wakeup_secondary_cpu_via_init(u32
phys_apicid, unsigned long start_ei
 /* reduce the number of lines printed when booting a large cpu count
system */
 static void announce_cpu(int cpu, int apicid)
 {
-       static int width, node_width, first = 1;
+       static int width, node_width, bspn = -1;
        static int current_node = NUMA_NO_NODE;
-       int node = early_cpu_to_node(cpu);
+       int bsp, node = early_cpu_to_node(cpu);

        if (!width)
                width = num_digits(num_possible_cpus()) + 1; /* + '#'
sign */
@@ -942,7 +942,7 @@ static void announce_cpu(int cpu, int apicid)
                node_width = num_digits(num_possible_nodes()) + 1; /* +
'#' */

        if (system_state < SYSTEM_RUNNING) {
-               if (first)
+               if (bspn == -1)
                        pr_info("x86: Booting SMP configuration:\n");

                if (node != current_node) {
@@ -954,10 +954,12 @@ static void announce_cpu(int cpu, int apicid)
                               node_width - num_digits(node), " ",
node);
                }

-               /* Add padding for the BSP */
-               if (first)
-                       pr_cont("%*s", width + 1, " ");
-               first = 0;
+               if (bspn == -1) {
+                       bsp = raw_smp_processor_id();
+                       bspn = cpumask_next(bsp, cpu_present_mask);
+               }
+               if (cpu == bspn)
+                       pr_cont("%*s#%d", width - num_digits(bsp), " ",
bsp);

                pr_cont("%*s#%d", width - num_digits(cpu), " ", cpu);
        } else
-- 
2.30.2