From 978370956d2046b19313659ce65ed12d5b996626 Mon Sep 17 00:00:00 2001 From: Chuansheng Liu Date: Tue, 7 Jan 2020 00:41:16 +0000 Subject: [PATCH] x86/mce/therm_throt: Do not access uninitialized therm_work It is relatively easy to trigger the following boot splat on an Ice Lake client platform. The call stack is like: kernel BUG at kernel/timer/timer.c:1152! Call Trace: __queue_delayed_work queue_delayed_work_on therm_throt_process intel_thermal_interrupt ... The reason is that a CPU's thermal interrupt is enabled prior to executing its hotplug onlining callback which will initialize the throttling workqueues. Such a race can lead to therm_throt_process() accessing an uninitialized therm_work, leading to the above BUG at a very early bootup stage. Therefore, unmask the thermal interrupt vector only after having setup the workqueues completely. [ bp: Heavily massage commit message and correct comment formatting. ] Fixes: f6656208f04e ("x86/mce/therm_throt: Optimize notifications of thermal throttle") Signed-off-by: Chuansheng Liu Signed-off-by: Borislav Petkov Acked-by: Tony Luck Link: https://lkml.kernel.org/r/20200107004116.59353-1-chuansheng.liu@intel.com --- arch/x86/kernel/cpu/mce/therm_throt.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/mce/therm_throt.c b/arch/x86/kernel/cpu/mce/therm_throt.c index b38010b..6c3e1c9 100644 --- a/arch/x86/kernel/cpu/mce/therm_throt.c +++ b/arch/x86/kernel/cpu/mce/therm_throt.c @@ -467,6 +467,7 @@ static int thermal_throttle_online(unsigned int cpu) { struct thermal_state *state = &per_cpu(thermal_state, cpu); struct device *dev = get_cpu_device(cpu); + u32 l; state->package_throttle.level = PACKAGE_LEVEL; state->core_throttle.level = CORE_LEVEL; @@ -474,6 +475,10 @@ static int thermal_throttle_online(unsigned int cpu) INIT_DELAYED_WORK(&state->package_throttle.therm_work, throttle_active_work); INIT_DELAYED_WORK(&state->core_throttle.therm_work, throttle_active_work); + /* Unmask the thermal vector after the above workqueues are initialized. */ + l = apic_read(APIC_LVTTHMR); + apic_write(APIC_LVTTHMR, l & ~APIC_LVT_MASKED); + return thermal_throttle_add_dev(dev, cpu); } @@ -722,10 +727,6 @@ void intel_init_thermal(struct cpuinfo_x86 *c) rdmsr(MSR_IA32_MISC_ENABLE, l, h); wrmsr(MSR_IA32_MISC_ENABLE, l | MSR_IA32_MISC_ENABLE_TM1, h); - /* Unmask the thermal vector: */ - l = apic_read(APIC_LVTTHMR); - apic_write(APIC_LVTTHMR, l & ~APIC_LVT_MASKED); - pr_info_once("CPU0: Thermal monitoring enabled (%s)\n", tm2 ? "TM2" : "TM1"); -- 2.7.4