I want to debug a mysterious hard system crash related to a secondary PCIe GPU. I suspect that Xen or Dom0 is crashing due to a fatal error, and I know it should be possible to obtain the logs via my machine’s physical serial port. But I’m not sure about how and I couldn’t find a document for it. The only document I found was logging into Dom0 via tty (Safe remote dom0 terminals | Qubes OS), but what I want is obtaining low-level logs, not a getty console.
I did a quick search and all the results are about laptop debugging via Intel’s USB 3.0 xHCI’s serial functionality. I need documentation for the plain-old serial port.
How do I specify a logging serial port? How do I obtain raw Xen logs and kernel logs from the port? Could anyone point give me a pointer to the relevant Xen/Linux/Qubes documentation? Thanks!