Re: kern/54143 (kernel crashes with amd64 CURRENT iso in virtualbox)

[Maxime Villard <max%m00nbsd.net@localhost>]

Basically it faults on rdmsr(MSR_LS_CFG2), which means the MSR does not
exist in VirtualBox. Three things that I find surprising:

 * At the beginning of x86_errata() we leave if there is a hypervisor, yet in
   your case it seems we don't leave. Maybe it means VirtualBox does not set
   CPUID2_RAZ?

 * The rdmsr is not incorrect, it corresponds to errata #1091, which does
   affect PiR-B2 (0x800f82, your CPU). The AMD spec says the workaround
   should be "Program MSRC001_102D[34] to 1b". That's exactly what we're
   doing, so there is no apparent reason for it to fault, except if VirtualBox
   does not whitelist it correctly.

 * It looks like we are the only ones to apply this errata, I don't see it in
   Linux or any of the other BSDs. Maybe we shouldn't be applying it?

I think I will add #if0 around this errata for now.