One more for the road. So, I have a little old SPARC64 niagara 2 box, which is a strange beast for a number of reasons. The onboard NIC is a strange bespoke S

One more for the road. So, I have a little old SPARC64 niagara 2 box, which is a strange beast for a number of reasons. The onboard NIC is a strange bespoke Sun-created Ethernet card, over the PCIe bus. Since it's a SPARC in 202x, it's not really well tested or supported, so updating is always fun. One day, I lost power, and on next boot, it booted a newer kernel, and the kernel panicked. I rapidly determined this was from trying and failing to initialize the NIC, and attempting to bisect it turned out to be really exciting - after getting impossible bisect results, I realized, once I booted a "working" kernel, all successive kernels worked until a cold boot. The problem, you see, was that they had changed some things about the PCIe initialization to enable certain kinds of memory protection features. The actual memory protection feature works fine on this hardware - but the _check_ of whether the feature is supported causes the machine to panic. But once the machine is booted, it doesn't try to re-initialize this on warm boot, so it doesn't trip this problem.