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BBerg7
New Contributor I
1,961 Views

Linux proc/interrupts ERR counter increments for each CPU on periodic SMI event.

Hi,

I have the following problem. When periodic SMI events are enabled the APIC error interrupt gets triggered for each CPU. I run the tests on a board with E3845 and use the default interval of 64 seconds.

Each 64 seconds Linux ERR count are increased with 4. If I disable periodic events, the ERR counter will stay at 0. The SMI is generated by chipset and thus it triggers all CPUs.

Any idea of how to avoid this behavior except disabling SMIs? I expect that chipset SMIs should not end up as APIC error interrupts, like spurious interrupts will do. Other than the 4 APIC error interrupts each minute, I have no abnormal interrupt activity.

Any ideas?

Best regards,

B-O

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9 Replies
BBerg7
New Contributor I
223 Views

As additional input consider the drawing below from Multiprocessor Specification 1.4. According to this drawing the SMI# signal are directly connected to the CPUs. Some sources on internet says that the error interrupts are generated by the I/O APIC, but since there are no SMI# connection external to the CPUs, how can the internal chipset SMI# generate an error interrupt for each CPU on periodic events?

How are the APICs routed in Bay Trail? Perhaps there are some chipset register for the settings as the PMU may be an external source of SMI# ?

Best regards,

B-O

Adolfo_S_Intel
Moderator
223 Views

Hello B-O

We are investigating your case and will reply with more information as soon as possible.

Best Regards,

Adolfo

BBerg7
New Contributor I
223 Views

Thank you Adolfo!

Best regards,

B-O

CarlosAM_INTEL
Moderator
223 Views

Hello B-O,

Thanks for your updates.

The information that may help you is stated in the erratum VLI54, on page 30 of the http://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/atom-e3800-family-... Intel(R) Atom(TM) Processor E3800 Product Family Specification Update.

Please let us know if this information is useful to you.

Best Regards,

Carlos_A.

BBerg7
New Contributor I
223 Views

Hi Carlos!

Unfortunately it doesn't help me. The thing is that when the SMM periodic timer is enabled a SMI will be generated when the period expires. The default period is 64 seconds. When the timer expires the SMI will trigger all CPUs to enter the SMM. However, as a side effect the I/O APIC error interrupt will also be triggered for each CPU, causing 4 interrupts for each SMI.

The I/O APIC error interrupt may also be triggered by other SMIs, but in my case the only the SMM periodic timer is active when Linux is running. It's used for monitoring CPU temperatures when ACPI is enabled. When active it triggers a SMI every minute and thus every minute the Linux ERR counter in proc/interrupts is incremented by 4, which is the number of cores in the E3845 board I use.

So the question is, how can I use chipset SMIs without triggering I/O APIC errors? As I assume that Linux does a good job programming the local APICs and the I/O APIC, I think the problem needs to be solved on the firmware level.

Best regards,

B-O

CarlosAM_INTEL
Moderator
223 Views

Hello B-O,

Thanks for your reply.

We will contact you via email in order to help you.

Best Regards,

Carlos_A.

BBerg7
New Contributor I
223 Views

Thanks!

Best regards,

B-O

BBerg7
New Contributor I
223 Views

Hi Carlos,

Unfortunately the IPS didn't work at all, so I can't raise the question there. Clicking on the Intel Premium Support link in the IBL, just load a new page for the IBL. So I'm stuck in a loop and can't access the IPS. Can you help fixing the IPS?

Best regards,

B-O

CarlosAM_INTEL
Moderator
223 Views

Hello B-O,

Thanks for your reply.

We will contact you via email in order to help you.

Best Regards,

Carlos_A.

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