[tip: ras/urgent] x86/mce/therm_throt: Undo thermal polling properly on CPU offline

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the ras/urgent branch of tip:

Commit-ID:     bf69bac4d3ef188ee8cf536a31ecbb230a8ba91a
Gitweb:        https://git.kernel.org/tip/bf69bac4d3ef188ee8cf536a31ecbb230a8ba91a
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Tue, 25 Feb 2020 14:55:15 +01:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Tue, 25 Feb 2020 15:05:56 +01:00

x86/mce/therm_throt: Undo thermal polling properly on CPU offline

Chris Wilson reported splats from running the thermal throttling
workqueue callback on offlined CPUs. The problem is that that callback
should not even run on offlined CPUs but it happens nevertheless because
the offlining callback thermal_throttle_offline() does not symmetrically
undo the setup work done in its onlining counterpart. IOW,

 1. The thermal interrupt vector should be masked out before ...

 2. ... cancelling any pending work synchronously so that no new work is
 enqueued anymore.

Do those things and fix the issue properly.

 [ bp: Write commit message. ]

Fixes: f6656208f04e ("x86/mce/therm_throt: Optimize notifications of thermal throttle")
Reported-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Tested-by: Pandruvada, Srinivas <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/158120068234.18291.7938335950259651295@skylake-alporthouse-com
---
 arch/x86/kernel/cpu/mce/therm_throt.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/therm_throt.c b/arch/x86/kernel/cpu/mce/therm_throt.c
index 58b4ee3..5d8971c 100644
--- a/arch/x86/kernel/cpu/mce/therm_throt.c
+++ b/arch/x86/kernel/cpu/mce/therm_throt.c
@@ -487,8 +487,12 @@ static int thermal_throttle_offline(unsigned int cpu)
 	struct thermal_state *state = &per_cpu(thermal_state, cpu);
 	struct device *dev = get_cpu_device(cpu);
 
-	cancel_delayed_work(&state->package_throttle.therm_work);
-	cancel_delayed_work(&state->core_throttle.therm_work);
+	/* Mask the thermal vector before draining evtl. pending work */
+	l = apic_read(APIC_LVTTHMR);
+	apic_write(APIC_LVTTHMR, l | APIC_LVT_MASKED);
+
+	cancel_delayed_work_sync(&state->package_throttle.therm_work);
+	cancel_delayed_work_sync(&state->core_throttle.therm_work);
 
 	state->package_throttle.rate_control_active = false;
 	state->core_throttle.rate_control_active = false;