Software Tuning, Performance Optimization & Platform Monitoring
Discussion regarding monitoring and software tuning methodologies, Performance Monitoring Unit (PMU) of Intel microprocessors, and platform updating.

Reading QPI Routing Table

robchip
Beginner
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Hi there!

Is there a way to read out the QPI routing table of a processor? I'm looking for something similar to the "cpuid" instruction that can be used to query the hardware directly. Since I'm not working with either Linux, or Windows I cannot use already existing programs...

Is there a way to get this information from the hardware? -  I guess this is done differently for different processors, at the moment I'm especially interested in the XEON 7500 Series...

Thank's in advance for any input!

Robert

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9 Replies
Patrick_F_Intel1
Employee
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Hello Robchip, There is a way to do this but it is not published. The manual http://www.intel.com/Assets/en_US/PDF/datasheet/323341.pdf mentions an overview of how to do it in section 13.2.1.1 'System Discovery' but the detail is not sufficient to actually decode the routing tables. It will probably take a lot of work to get the information public. Why do you want the information? Pat
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Bernard
Valued Contributor I
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You can consult relevant to QPI chipset specification.
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wonjun_s_
Beginner
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Hi. 

Could you tell me how to access the control register for Routing Layer in QPI ??

I want to modify RTA(Router Table Array) for research purpose.

Now I'm using CentOS6, but I couldn't find any piece of codes and "base address" related with QPI.

any hints? 

Thanks.

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Bernard
Valued Contributor I
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I suppose that the access is done by MSR address space.

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wonjun_s_
Beginner
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thanks for reply. :-)

as you said. I also think so.

wrmsr(), rdmsr() may be used to control that.

But what I want to know what is the base address (or offset) to access registers for Routing Layer

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Patrick_F_Intel1
Employee
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Hello Wonjun,

As I mentioned in the other thread, this info has not been publicly disclosed.

Pat

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Bernard
Valued Contributor I
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wonjun s. wrote:

thanks for reply. :-)

as you said. I also think so.

wrmsr(), rdmsr() may be used to control that.

But what I want to know what is the base address (or offset) to access registers for Routing Layer

An option of last resort will be hooking kernel debugger and try to locate MSR register with the help of kd.Not an easy task when the address is not available or disclosed.

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Patrick_F_Intel1
Employee
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Just to save the time of anyone thinking of pursuing the kernel debugger route...I doubt that using the kernel debugger will be fruitful in this case.

Pat

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Bernard
Valued Contributor I
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Yes that's true.For exmaple access to this feature can be available from SMM mode only.

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