Hi Peter,

On 6 Mar 2018, at 16:15, Peter Grehan wrote:
>  Exception 14 is a page fault (SDM Vol3 ch 6.15). The exception type is 
> "fault" which means it is delivered at the address it was detected at.
>  This cascaded very quickly into a triple-fault, so it looks like it could 
> possibly be an issue with the stack. One debug tool you do have is to get a 
> register dump on exit, with 'bhyvectl --get-all --vm=<your vn name>'.
>  For a page-fault, the virtual address that resulted in the fault will be in 
> the CR2 register.

I don’t see a CR2 register in the output of bhyvectl --get-all, I was looking 
for that too.

>  From the code at the faulting address:
>  > 0000000000102a50 <cons_init>:
>  >    102a50:       push   rbx
>  >    102a51:       call   103540 <hypervisor_detect>
>  >    102a56:       cmp    WORD PTR [rip-0x102a5c],0x0        # 2 
> <current_lwp+0x2>
>  It's using RIP-relative addressing here, but objdump seems to think this may 
> be an offset in the current_lwp structure - is it possible that may have an 
> uninitialized value ?

I’m pretty sure it’s tooling that’s displaying something off, since hopper is 
showing me this as

0x0000000000102a56         cmp        word [0x2], 0x0

Which is very similar to what r2 is giving me:

;-- cons_init:
0x00102a50      53             push rbx                    ; /arch/x86:43
0x00102a51      e8ea0a0000     call sym.hypervisor_detect  ; /arch/x86:47
0x00102a56      66833da4d5ef.  cmp word [0x00000002], 0    ; /arch/x86:62

>  (I don't believe this has anything to do with VGA).

Maybe I’m off with my analysis of the actual fault here, but how I understand
the source (assuming compilers work as I would expect, which is not always true)
the values here are initialised from values in the bios data area (which is
zeroed out on bhyve):

#define BIOS_COM1_BASE  0x400
#define BIOS_CRTC_BASE  0x463


        movw BIOS_COM1_BASE, %bx
        movw %bx, bios_com1_base
        movw BIOS_CRTC_BASE, %bx
        movw %bx, bios_crtc_base


         * If the BIOS says no CRTC is present use the serial console if
         * available.
        if (bios_crtc_base == 0)
prefer_serial = 1;

Here’s my full output from bhyvectl --get-all:

ID  Length      Name
0   128MB       sysmem
Address     Length      Segment     Offset      Prot  Flags
0           128MB       sysmem      0           RWX
efer[0]         0x0000000000000500
cr0[0]          0x0000000080010031
cr3[0]          0x000000000010b000
cr4[0]          0x0000000000002620
dr7[0]          0x0000000000000400
rsp[0]          0x0000000000100ff0
rip[0]          0x0000000000102a56
rax[0]          0x0000000000000000
rbx[0]          0x00000000003eaa2b
rcx[0]          0x0000000068622065
rdx[0]          0x0000000020657679
rsi[0]          0x0000000000100fd0
rdi[0]          0x0000000040000000
rbp[0]          0x0000000000000000
r8[0]           0x0000000000100fdc
r9[0]           0x0000000000100fd8
r10[0]          0x0000000000100fd4
r11[0]          0x0000000000000000
r12[0]          0x0000000000000000
r13[0]          0x0000000000000000
r14[0]          0x0000000000000000
r15[0]          0x0000000000000000
rflags[0]       0x0000000000010006
ds desc[0]      0x0000000000000000/0xffffffff/0x0000c093
es desc[0]      0x0000000000000000/0xffffffff/0x0000c093
fs desc[0]      0x0000000000000000/0xffffffff/0x0001c001
gs desc[0]      0x0000000000000000/0xffffffff/0x0001c001
ss desc[0]      0x0000000000000000/0xffffffff/0x0000c093
cs desc[0]      0x0000000000000000/0xffffffff/0x0000a09b
tr desc[0]      0x0000000000000000/0x00000000/0x0000008b
ldtr desc[0]    0x0000000000000000/0x0000ffff/0x00000082
gdtr[0]         0x0000000000378040/0x0000002f
idtr[0]         0x0000000000000000/0x0000ffff
cs[0]           0x0008
ds[0]           0x0018
es[0]           0x0018
fs[0]           0x0000
gs[0]           0x0000
ss[0]           0x0018
tr[0]           0x0000
ldtr[0]         0x0000
cr0_mask[0]             0xffffffff60000020
cr0_shadow[0]           0x0000000000000021
cr4_mask[0]             0xffffffffffe8f800
cr4_shadow[0]           0x0000000000000000
cr3_target_count[0]     0x0000000000000000
cr3_target0[0]          0x0000000000000000
cr3_target1[0]          0x0000000000000000
cr3_target2[0]          0x0000000000000000
cr3_target3[0]          0x0000000000000000
pinbased_ctls[0]        0x000000000000003f
procbased_ctls[0]       0x00000000f51865f2
procbased_ctls2[0]      0x00000000000010a2
gla[0]          0xfffffe0000c41000
gpa[0]          0x0000000000000000
entry_interruption_info[0]      0x0000000000000000
tpr_threshold[0]        0x0000000000000000
instruction_error[0]    0x0000000000000000
exit_ctls[0]            0x000000000033efff
entry_ctls[0]           0x00000000000093ff
host_pat[0]             0x0001050600070406
host_cr0[0]             0x000000008005003b
host_cr3[0]             0x0000000038045054
host_cr4[0]             0x00000000001726e0
host_rip[0]             0xffffffff81435290
host_rsp[0]             0xfffffe003218d700
vmcs_pointer[0] 0xffffffffffffffff
vmcs_exit_interruption_info[0]  0x0000000080000b0e
vmcs_exit_interruption_error[0] 0x0000000000000000
vmcs_guest_interruptibility[0]  0x0000000000000000
vmcs_exit_inst_length[0]        0x00000003
vmcs_exit_qualification[0]      0x0000000000000080
x2apic_state[0] 0
eptp[0]         0x000000003817905e
exception_bitmap[0]     0xffffffff
io_bitmap_a[0]  0
io_bitmap_b[0]  0
tsc_offset[0]   0x0000000000000000
msr_bitmap[0]           0x1adbc000
MSR_TSC             [0]         R-
MSR_EFER            [0]         RW
MSR_STAR            [0]         RW
MSR_LSTAR           [0]         RW
MSR_CSTAR           [0]         RW
MSR_SF_MASK         [0]         RW
MSR_FSBASE          [0]         RW
MSR_GSBASE          [0]         RW
MSR_KGSBASE         [0]         RW
vpid[0]         0x0011
guest_pat[0]            0x0000000000000000
guest_sysenter_cs[0]    0
guest_sysenter_sp[0]    0
guest_sysenter_ip[0]    0
exit_reason[0]  0
rtc nvram[000]: 0x34
rtc time 0x5a9ebfd2: Tue Mar 06 16:20:34 2018
Capability "hlt_exit" is set on vcpu 0
Capability "mtrap_exit" is not set on vcpu 0
Capability "pause_exit" is set on vcpu 0
Capability "unrestricted_guest" is set on vcpu 0
Capability "enable_invpcid" is set on vcpu 0
active cpus:     0
suspended cpus:  0
pending:        n/a
current:        n/a
vcpu0 stats:
number of times in/out was intercepted          0
number of times cpuid was intercepted           3
vm exits due to nested page fault               13
vm exits for instruction emulation              0
number of vm exits for unknown reason           0
number of times astpending at exit              0
number of times idle requested at exit          0
number of vm exits handled in userspace         14
number of times rendezvous pending at exit      0
number of vm exits due to exceptions            3
number of NMIs delivered to vcpu                0
number of ExtINTs delivered to vcpu             0
Resident memory                                 69632
Wired memory                                    0
vcpu total runtime                              3112708
EOI without any in-service interrupt            0
error interrupts generated by vlapic            0
timer interrupts generated by vlapic            0
corrected machine check interrupts generated by vlapic  0
lvts triggered[0]                               0
lvts triggered[1]                               0
lvts triggered[2]                               0
lvts triggered[3]                               0
lvts triggered[4]                               0
lvts triggered[5]                               0
lvts triggered[6]                               0
ipis sent to vcpu[0]                            0
ipis sent to vcpu[1]                            0
ipis sent to vcpu[2]                            0
ipis sent to vcpu[3]                            0
ipis sent to vcpu[4]                            0
ipis sent to vcpu[5]                            0
ipis sent to vcpu[6]                            0
ipis sent to vcpu[7]                            0
ipis sent to vcpu[8]                            0
ipis sent to vcpu[9]                            0
ipis sent to vcpu[10]                           0
ipis sent to vcpu[11]                           0
ipis sent to vcpu[12]                           0
ipis sent to vcpu[13]                           0
ipis sent to vcpu[14]                           0
ipis sent to vcpu[15]                           0
number of ticks vcpu was idle                   0
vcpu migration across host cpus                 1
total number of vm exits                        19
vm exits due to external interrupt              0
Number of vpid invalidations saved              0
Number of vpid invalidations done               1
number of times hlt was intercepted             0
number of times %cr access was intercepted      0
number of times rdmsr was intercepted           0
number of times wrmsr was intercepted           0
number of monitor trap exits                    0
number of times pause was intercepted           0
vm exits due to interrupt window opening        0
vm exits due to nmi window opening              0


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