P2p capabilities of the Alder Lake (Z690) platform

[JCIe]

Hi

I've been testing p2p transfers on a z690 system with a 12700k CPU. Two PCIe devices were placed in various slots and both p2p write (MWr TLP) and p2p read (MRd TLP). The results were measured in both software and at the PCIe bus.

My results

P2p write (MWr TLP) works with:

• Both devices connected to CPU PCIe
• One device connected to chipset PCIe and one to CPU PCIe

But not for both devices connected to chipset PCIe. Packets are sent but does not reach the target device.

P2p read (MRd TLP) does not work for any any slots used. When MRds are issued a completion from root  (id 000:00:0) with "unsupported request" status is received.

My questions are

• Can the chipset support p2p write between devices connected to chipset PCIe? I.e. can the chipset act as a PCIe switch?
• Can the platform support p2p read at all? And if so for CPU or chipset PCIe? I'm guessing that there may be some security feature blocking this.

I know that bios settings and board configuration may affect these things so for my questions I'm wondering if the features are supported at all by the platform, and what settings are needed to get it working.

[DeividA_Intel]

Hello JCIe,  

Thank you for posting on the Intel® communities. I am sorry to know that you are having issues with your Intel® Core™ i7-12700K Processor.

In order to better assist you, please provide the following:  

1. Run the Intel® System Support Utility (Intel® SSU) to gather more details about the system.  

• Download the Intel® SSU and save the application on your computer: https://www.intel.com/content/www/us/en/download/18377/intel-system-support-utility-for-windows.html  
• Open the application, check the "Everything" checkbox, and click "Scan" to see the system and device information. The Intel® SSU defaults to the "Summary View" on the output screen following the scan. Click the menu where it says "Summary" to change to "Detailed View".  
• To save your scan, click Next and click Save.  

2. What does "P2P" means? What are you referring to?

3. What are the devices connected to the PCI-E slots?

4. What is the tool used to run the test?

5. Can you provide more details about the issue?

6. Have you checked this behavior with the motherboard manufacturer?

Regards,  

Deivid A. 

Intel Customer Support Technician 

[JCIe]

Hello Deivid!
Thanks for your response. I'm working on engineering level with FPGA based PCIe devices. So I think someone with low level knowledge of the platforms PCIe bus needs to answer this.

1. I'm running Linux. The motherboards is an Asrock z690 PRO RS.

2. Peer-to-Peer, Communication directly between PCIe devices.

3. FPGA-based cards, Nvidia GPUs and Samsung SSD

4. I'm using a Lecroy bus analyser to capture the PCIe traffic.

5. MWr TLP between 2 device connect to chipset PCIe slots I can see the outgoing TLPs from one device (and they look correct), but they never reach the target device. MRd TLPs does also look correct at the device issuing the reads but they never reach the target device. The issuing device receives an "unsoppurted request" from root. See attached pictures.

6. I'm interested in the general capabilities of the platform for engineering purposes. So I expect intel to know the capabilities of the plattform, and if there are limitations for specific motherboards that's a secondary issue.

[DeividA_Intel]

Hello JCIe, 

Thank you for the information provided 

I will proceed to check the issue internally and post back soon with more details. 

Best regards, 

Deivid A.  

Intel Customer Support Technician 

[DeividA_Intel]

Hello JCIe, 

Thanks for your patience. Based on the research performed, P2P is about several systems or components connected to each other through the network instead of a server. If this is your case, you will need to check this with the motherboard manufacturer (Asus) since the processor is not one of the requirements for this process.

Regarding the chipset, Asus may have customized it, so you will need to check with them to know how it is configured.

Best regards, 

Deivid A.  

Intel Customer Support Technician 

[JCIe]

Hi Deivid,

The p2p transfer is between two PCIe devices in one alder lake system. There is no network, only the PCIe bus. You (Intel) have answered similar questions before for other platforms, but there was a solid month of escalation before the question reached someone with this knowledge.

So please try again, otherwise we, and our customers will have to avoid building Intel systems, and that seems a bit drastic.

Regards

[DeividA_Intel]

Hello JCIe,

I am sorry to know that the answer was not the one that you needed. I will check again to confirm the information and I will let you know as soon as I have any details.

Thanks for your comprehension.

Regards,  

Deivid A. 

Intel Customer Support Technician

[DeividA_Intel]

Hello JCIe, 

Thanks for your patience. In order to continue with the investigation, I will need the following:

1. What is the Linux distributor that you are using?

2. Run the Intel® System Support Utility (Intel® SSU) to gather more details about the system.  

• Download the Intel® SSU and save the application on your computer: https://www.intel.com/content/www/us/en/download/18895/intel-system-support-utility-for-the-linux-operating-system.html
• Open the application, check the "Everything" checkbox, and click "Scan" to see the system and device information. The Intel® SSU defaults to the "Summary View" on the output screen following the scan. Click the menu where it says "Summary" to change it to "Detailed View".  
• To save your scan, click Next and click Save.  

Regards,  

Deivid A.  

Intel Customer Support Technician  

[JCIe]

Hello Deivid,

Thanks for your reply, I will gather the requested information. However I'm leaving for my summer vacation so it will be around 4 weeks, but I hope we can continue to make progress then

[DeividA_Intel]

Hello JCIe, 

Thanks for your reply.  I understand the situation, I will wait for your response in 4 weeks.

Enjoy your vacations!

Regards,  

Deivid A.  

Intel Customer Support Technician  

[DeividA_Intel]

Hello JCIe,  

I reviewed your post, please let me know if the issue was resolved, if not, do not hesitate, just reply back.

Regards,  

Deivid A.  

Intel Customer Support Technician  

[DeividA_Intel]

Hello JCIe,  

I was checking your thread and see that we have not heard back from you.  

I’m going to close your post, but if you need further assistance, please do not hesitate in contacting us. 

Regards,  

Deivid A.  

Intel Customer Support Technician