linux-kernel - [PATCH] x86/hpet: Do not use smp_processor

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Message-Id: <20170620093154.18472-1-bp@alien8.de>
Date:   Tue, 20 Jun 2017 11:31:54 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/hpet: Do not use smp_processor_id() in preemptible code

From: Borislav Petkov <bp@...e.de>

When hpet=force is supplied on the kernel command line and the HPET
supports the Legacy Replacement Interrupt Route option (HPET_ID_LEGSUP),
the legacy interrupts init code uses the boot CPU's mask initially by
calling smp_processor_id() assuming that it is running on the BSP.

And it does run on the BSP but the code region is preemptible and the
preemption check fires.

Simply use the BSP's id directly to avoid the warning.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/kernel/hpet.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 89ff7af2de50..16f82a3aaec7 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -285,7 +285,7 @@ static void hpet_legacy_clockevent_register(void)
 	 * Start hpet with the boot cpu mask and make it
 	 * global after the IO_APIC has been initialized.
 	 */
-	hpet_clockevent.cpumask = cpumask_of(smp_processor_id());
+	hpet_clockevent.cpumask = cpumask_of(boot_cpu_data.cpu_index);
 	clockevents_config_and_register(&hpet_clockevent, hpet_freq,
 					HPET_MIN_PROG_DELTA, 0x7FFFFFFF);
 	global_clock_event = &hpet_clockevent;
-- 
2.13.0