[SRU][Xenial][PATCH] x86/speculation: Remove redundant arch_smt_update() invocation

[Juerg Haefliger]

From: Zhenzhong Duan <zhenzhong.duan at oracle.com>

With commit a74cfffb03b7 ("x86/speculation: Rework SMT state change"),
arch_smt_update() is invoked from each individual CPU hotplug function.

Therefore the extra arch_smt_update() call in the sysfs SMT control is
redundant.

Fixes: a74cfffb03b7 ("x86/speculation: Rework SMT state change")
Signed-off-by: Zhenzhong Duan <zhenzhong.duan at oracle.com>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Cc: <konrad.wilk at oracle.com>
Cc: <dwmw at amazon.co.uk>
Cc: <bp at suse.de>
Cc: <srinivas.eeda at oracle.com>
Cc: <peterz at infradead.org>
Cc: <hpa at zytor.com>
Link: https://lkml.kernel.org/r/e2e064f2-e8ef-42ca-bf4f-76b612964752@default

CVE-2018-12126
CVE-2018-12127
CVE-2018-12130

(cherry picked from commit 34d66caf251df91ff27b24a3a786810d29989eca)
Signed-off-by: Juerg Haefliger <juergh at canonical.com>
---
 kernel/cpu.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 5d48161476a1..d9465123f7ec 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -896,10 +896,8 @@ static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
 		 */
 		cpuhp_offline_cpu_device(cpu);
 	}
-	if (!ret) {
+	if (!ret)
 		cpu_smt_control = ctrlval;
-		arch_smt_update();
-	}
 	cpu_maps_update_done();
 	return ret;
 }
@@ -910,7 +908,6 @@ static int cpuhp_smt_enable(void)
 
 	cpu_maps_update_begin();
 	cpu_smt_control = CPU_SMT_ENABLED;
-	arch_smt_update();
 	for_each_present_cpu(cpu) {
 		/* Skip online CPUs and CPUs on offline nodes */
 		if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
-- 
2.20.1