x86: Fix thermal throttling reporting after kexec
PATCH 1/1 x86: Fix thermal throttling reporting after kexec
From: Andi Kleen <[email protected]>
The per CPU thermal vector init code checks if the thermal vector is already installed and complains and bails out if it is.
This happens after kexec, as kernel shut down does not clear the thermal vector APIC register.
This causes two problems:
So we always do not fully initialize thermal reports after kexec. The CPU is still likely initialized, as the previous kernel should have done it. But we don't set up the software pointer to the thermal vector, so reporting may end up with a unknown thermal interrupt message.
Also it complains for every logical CPU, even though the value is actually derived from BP only.
The problem is that we end up with one message per CPU, so on larger systems it becomes very noisy and messes up the otherwise nicely formatted CPU bootup numbers in the kernel log.
Just remove the check. I checked the code and there's no valid code paths where the thermal init code for a CPU could be called multiple times.
Why the kernel does not clean up this value on shutdown:
The thermal monitoring is controlled per logical CPU thread. Normal shutdown code is just running on one CPU. To disable it we would need a broadcast NMI to all CPUs on shut down. That's overkill for this. So we just ignore it after kexec.
v2: Updated commit log to discuss why the value is not cleaned up on shutdown.
--- arch/x86/kernel/cpu/mcheck/therm_throt.c | 8 -------- 1 file changed, 8 deletions(-)
arch/x86/kernel/cpu/mcheck/therm_throt.c +0 -8
@@ -503,14 +503,6 @@ void intel_init_thermal(struct cpuinfo_x86 *c)return ; } -/* Check whether a vector already exists */ -if (h &APIC_VECTOR_MASK ) { -printk (KERN_DEBUG -"CPU%d: Thermal LVT vector (%#x) already installed\n" , - cpu, (h &APIC_VECTOR_MASK )); -return ; - } -/* early Pentium M models use different method for enabling TM2 */ if (cpu_has (c,X86_FEATURE_TM2 )) {if (c->x86 ==6 && (c->x86_model ==9 || c->x86_model ==13 )) {
Signature · 1 line
2.4.3
Quoted 38 lines · Andi Kleen
From: Andi Kleen <[email protected]>
The per CPU thermal vector init code checks if the thermal vector is already installed and complains and bails out if it is.
This happens after kexec, as kernel shut down does not clear the thermal vector APIC register.
This causes two problems:
So we always do not fully initialize thermal reports after kexec. The CPU is still likely initialized, as the previous kernel should have done it. But we don't set up the software pointer to the thermal vector, so reporting may end up with a unknown thermal interrupt message.
Also it complains for every logical CPU, even though the value is actually derived from BP only.
The problem is that we end up with one message per CPU, so on larger systems it becomes very noisy and messes up the otherwise nicely formatted CPU bootup numbers in the kernel log.
Just remove the check. I checked the code and there's no valid code paths where the thermal init code for a CPU could be called multiple times.
Why the kernel does not clean up this value on shutdown:
The thermal monitoring is controlled per logical CPU thread. Normal shutdown code is just running on one CPU. To disable it we would need a broadcast NMI to all CPUs on shut down. That's overkill for this. So we just ignore it after kexec.
Quoted 3 lines
v2: Updated commit log to discuss why the value is not cleaned up on shutdown.
Signed-off-by Andi Kleen <[email protected]>
Quoted 39 lines · Thomas Gleixner
Quoted 38 lines · Andi Kleen
From: Andi Kleen <[email protected]>
The per CPU thermal vector init code checks if the thermal vector is already installed and complains and bails out if it is.
This happens after kexec, as kernel shut down does not clear the thermal vector APIC register.
This causes two problems:
So we always do not fully initialize thermal reports after kexec. The CPU is still likely initialized, as the previous kernel should have done it. But we don't set up the software pointer to the thermal vector, so reporting may end up with a unknown thermal interrupt message.
Also it complains for every logical CPU, even though the value is actually derived from BP only.
The problem is that we end up with one message per CPU, so on larger systems it becomes very noisy and messes up the otherwise nicely formatted CPU bootup numbers in the kernel log.
Just remove the check. I checked the code and there's no valid code paths where the thermal init code for a CPU could be called multiple times.
Why the kernel does not clean up this value on shutdown:
The thermal monitoring is controlled per logical CPU thread. Normal shutdown code is just running on one CPU. To disable it we would need a broadcast NMI to all CPUs on shut down. That's overkill for this. So we just ignore it after kexec.
Quoted 5 lines
Quoted 3 lines
v2: Updated commit log to discuss why the value is not cleaned up on shutdown.
Signed-off-by Andi Kleen <[email protected]>Reviewed-by Thomas Gleixner <[email protected]>
Applied,
thanks!
Signature · 4 lines
Regards/Gruss,
Boris.
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