linux-kernel - [PATCH v2 9/9] powerpc/pseries: Honour current SMT state when DLPAR onlining CPUs

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Date:   Wed, 28 Jun 2023 12:05:58 +0200
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        mpe@...erman.id.au, npiggin@...il.com, christophe.leroy@...roup.eu,
        tglx@...utronix.de, dave.hansen@...ux.intel.com, mingo@...hat.com,
        bp@...en8.de
Subject: [PATCH v2 9/9] powerpc/pseries: Honour current SMT state when DLPAR onlining CPUs

From: Michael Ellerman <mpe@...erman.id.au>

Integrate with the generic SMT support, so that when a CPU is DLPAR
onlined it is brought up with the correct SMT mode.

Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
---
 arch/powerpc/platforms/pseries/hotplug-cpu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 61fb7cb00880..e62835a12d73 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -398,6 +398,14 @@ static int dlpar_online_cpu(struct device_node *dn)
 		for_each_present_cpu(cpu) {
 			if (get_hard_smp_processor_id(cpu) != thread)
 				continue;
+
+			if (!topology_is_primary_thread(cpu)) {
+				if (cpu_smt_control != CPU_SMT_ENABLED)
+					break;
+				if (!topology_smt_thread_allowed(cpu))
+					break;
+			}
+
 			cpu_maps_update_done();
 			find_and_update_cpu_nid(cpu);
 			rc = device_online(get_cpu_device(cpu));
-- 
2.41.0