23.01 Hardware Errata and NG 8916

[forum1]

The current 23.01 hardware errata includes the following:

Devices based on “ADI” or “RCC” hardware, such as the 4860, 8860, and potentially other similar models, may have issues with the ichsmb0 and/or ehci0 devices encountering an interrupt loop, leading to higher than usual CPU usage (NG 8916). This can typically be worked around by disabling the affected device. For example, by placing the following in /boot/loader.conf.local: hint.ichsmb.0.disabled=1

I’m wondering:

1. Where can I find more on the details of issue “NG 8916”? My searches thus far haven’t come up with anything. Barring more material to review:
2. How common is this issue and thus how likely is it that the workaround will be required?
3. What are the ramifications of the workaround? i.e. is there anything in pfSense that relies on this SMBus device that will not function when it’s disabled? Are the USB ports still fully functional?
4. What are the plans for a more elegant fix?

[jimp]

1. The reference number is for the Netgate internal Redmine, which isn't public.
2. We are not sure as we have limited hardware from those lines remaining for testing, given that they are older/EOL devices. We only know for certain that it affects 4860, but we don't have data from all of the related models that were similar.
3. It only disables the LED status indicators on those platforms, so it's not critical.
4. We're looking into what, if anything, can be done for the next release (23.05), it's too early to know what will happen there.

[forum1]

@jimp Thanks for the info. This is quite relevant to me as I have a 4860 on hand that I was planning to test with and ultimately plan to update additional 4860 units. From what you've said, I will assume that there is no maybe about it with the 4860 (no other known factors that would avoid the interrupt loop) and that the workaround will be required. While the status LEDs are not critical, it would be nice for them to continue functioning since we do get into situations where they are helpful, so I would be eager to see a fix.