[Linux-aus] strange NVMe errors when USB is busy

[David Tekwie]

Hi Russell,

There seems to be a lot going on with your root complex here.
Have you tried this?

  lspci -t

You should get an output that looks something like this:

  -+-[0000:00]---00.0
 | +--14.0 (USB Controller)
 | +--1c.0
 | +--0d.0 (NVMe SSD)
 | +--01.0

A point to note also is that if the USB controller and NVMe SSD are under
the same PCIe root, then they might be contending for resources. But if
they are on different roots, then the issue might be power, interrupts, or
CPU load rather than direct PCIe contention as alluded to above.

Also, here's a neat way to get a detailed PCIe lane allocation and speeds:

  lspci -vvv | grep -iE "PCI bridge|NVMe|USB" -A 20

Note that running the above may show link speeds such as:  LnkSta: Speed
8GT/s, Width x4, but it can also be helpful to identify if a device is
being downgraded due to load issues.

But yes, try to dump out the output of "lspci -t" and let's see if there's
anything worth noting from that output.

Hope that helps.

Cheers.

On Mon, Jan 27, 2025 at 2:57 PM Russell Coker via linux-aus <
linux-aus at lists.linux.org.au> wrote:

> On Monday, 27 January 2025 12:22:06 AEDT Steven Ellis via linux-aus wrote:
> > Is there a chance that the USB is on the same overall BUS as the PCIe of
> > the affected NVMe?
>
> I've attached the output of "lspci -t".
>
> 0d:00.0 Non-Volatile memory controller: Sandisk Corp WD PC SN810 / Black
> SN850
> NVMe SSD (rev 01)
> 00:14.0 USB controller: Intel Corporation C610/X99 series chipset USB xHCI
> Host Controller (rev 05)
> 01:00.4 USB controller: Hewlett-Packard Company Integrated Lights-Out
> Standard
> Virtual USB Controller (rev 03)
>
> The above seems to be the relevant lines from "lspci".  How do I determine
> how
> close these things are to each other in topology?
>
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