[PATCHv5 2/3] powerpc/setup: Handle the case when boot_cpuid greater than nr_cpus

[Pingfan Liu <piliu@redhat.com>]

If the boot_cpuid is smaller than nr_cpus, it requires extra effort to
ensure the boot_cpu is in cpu_present_mask. This can be achieved by
reserving the last quota for the boot cpu.

Note: the restriction on nr_cpus will be lifted with more effort in the
next patch

Signed-off-by: Pingfan Liu <piliu@redhat.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Cc: Wen Xiong <wenxiong@linux.ibm.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: kexec@lists.infradead.org
To: linuxppc-dev@lists.ozlabs.org
---
 arch/powerpc/kernel/setup-common.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c
index a07af8de6674..58a988c64dd2 100644
--- a/arch/powerpc/kernel/setup-common.c
+++ b/arch/powerpc/kernel/setup-common.c
@@ -456,8 +456,8 @@ struct interrupt_server_node {
 void __init smp_setup_cpu_maps(void)
 {
 	struct device_node *dn;
-	int shift = 0, cpu = 0;
-	int j, nthreads = 1;
+	int terminate, shift = 0, cpu = 0;
+	int j, bt_thread = 0, nthreads = 1;
 	int len;
 	struct interrupt_server_node *intserv_node, *n;
 	struct list_head *bt_node, head;
@@ -520,6 +520,7 @@ void __init smp_setup_cpu_maps(void)
 			for (j = 0 ; j < nthreads; j++) {
 				if (be32_to_cpu(intserv[j]) == boot_cpu_hwid) {
 					bt_node = &intserv_node->node;
+					bt_thread = j;
 					found_boot_cpu = true;
 					/*
 					 * Record the round-shift between dt
@@ -539,11 +540,21 @@ void __init smp_setup_cpu_maps(void)
 	/* Select the primary thread, the boot cpu's slibing, as the logic 0 */
 	list_add_tail(&head, bt_node);
 	pr_info("the round shift between dt seq and the cpu logic number: %d\n", shift);
+	terminate = nr_cpu_ids;
 	list_for_each_entry(intserv_node, &head, node) {
 
+		j = 0;
+		/* Choose a start point to cover the boot cpu */
+		if (nr_cpu_ids - 1 < bt_thread) {
+			/*
+			 * The processor core puts assumption on the thread id,
+			 * not to breach the assumption.
+			 */
+			terminate = nr_cpu_ids - 1;
+		}
 		avail = intserv_node->avail;
 		nthreads = intserv_node->len / sizeof(int);
-		for (j = 0; j < nthreads && cpu < nr_cpu_ids; j++) {
+		for (; j < nthreads && cpu < terminate; j++) {
 			set_cpu_present(cpu, avail);
 			set_cpu_possible(cpu, true);
 			cpu_to_phys_id[cpu] = be32_to_cpu(intserv_node->intserv[j]);
@@ -551,6 +562,14 @@ void __init smp_setup_cpu_maps(void)
 			    j, cpu, be32_to_cpu(intserv[j]));
 			cpu++;
 		}
+		/* Online the boot cpu */
+		if (nr_cpu_ids - 1 < bt_thread) {
+			set_cpu_present(bt_thread, avail);
+			set_cpu_possible(bt_thread, true);
+			cpu_to_phys_id[bt_thread] = be32_to_cpu(intserv_node->intserv[bt_thread]);
+			DBG("    thread %d -> cpu %d (hard id %d)\n",
+			    bt_thread, bt_thread, be32_to_cpu(intserv[bt_thread]));
+		}
 	}
 
 	list_for_each_entry_safe(intserv_node, n, &head, node) {
-- 
2.31.1