illumos gate

Testing a BE for #13795, booting into a BE caused bhyve to exit with the following:

[2021-06-02T14:20:15.602943000Z]  INFO: zoneadmd/6789 on bob: (stream=stderr)
    vm exit[0]
        reason          VMX
        rip             0xfffffffffbaf03b6
        inst_length     2
        status          0
        exit_reason     44 (APIC access)

[2021-06-02T14:20:15.603164000Z]  INFO: zoneadmd/6789 on bob: (stream=stderr)
        qualification   0x0000000000000204
        inst_type               0
        inst_error              0

This happened after the 'DEBUG enabled' message on the console (so after the kernel was loaded):

illumos Version zfs-crypto-dnode-0-g72d3a7deb1 64-bit
DEBUG enabled

[NOTICE: Zone halted]

Restarting the instance with the same BE, and it booted just fine after that, so I haven't been able to recreate it again, but wanted to capture it in case others hit it.

This was on joyent_20201118T153314Z, so it's not the absolutely most recent, but not terribly ancient either.

I can't be sure this was the same code as when it occurred, but after rebooting, the instruction in question does at least look plausible (specific instruction is noted with asterisks):

> 0xfffffffffbaf03b6::dis
local_apic_read:                pushq  %rbp
local_apic_read+1:              movq   %rsp,%rbp
local_apic_read+4:              pushq  %rdi
local_apic_read+5:              movl   %edi,%edi
local_apic_read+7:              subq   $0x8,%rsp
local_apic_read+0xb:            movq   -0x3bae5c52(%rip),%rax   <apicadr>
local_apic_read+0x12:           leaq   (%rax,%rdi,4),%rax
** local_apic_read+0x16:           movl   (%rax),%eax **
local_apic_read+0x18:           leave
local_apic_read+0x19:           ret