FWIW, I was having similar kernel panics on my HP DL380G8 today. Two Xeon E5-2620 2 GHz, microcode version 0x71a. It's happened before, but only on a reboot.

Today, the kernel panics weren't consistent as to which CPU it was. I saw it get as high as CPU 22 and as low as CPU 3.

I was viewing POST via iLO remote console. After about an hour of allowing it to reboot on its own or with my manually resetting it via iLO GUI, I went to my data center and turned on the monitor and switched to the KVM channel the server was on. It came back up then. HTH.