Xen kernel fails to boot, d0v1 triple fault looks like the cuplrit

[Pratyush Yadav]

On Mon, May 21, 2018 at 2:33 PM, Roger Pau Monné <roger.pau at citrix.com>
wrote:
> Please try to avoid top posting.

Sorry, I didn't know. I Googled top posting just now, and realized it is
inconvenient for the reader.

> Hm, it seems like dbg_stack is not properly allocated. Can you please
> try the above debug patch and paste the boot log?
>
> ---8<---
> diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
> index 301461420874..8854242b4bf5 100644
> --- a/sys/amd64/amd64/mp_machdep.c
> +++ b/sys/amd64/amd64/mp_machdep.c
> @@ -304,6 +304,7 @@ init_secondary(void)
>
>         /* Save the per-cpu pointer for use by the DB# handler. */
>         np = ((struct nmi_pcpu *) &dbg_stack[PAGE_SIZE]) - 1;
> +printf("ID %d dbg_stack: %p per-cpu: %p\n", cpu, dbg_stack, np);
>         np->np_pcpu = (register_t) pc;
>
>         wrmsr(MSR_FSBASE, 0);           /* User value */
> @@ -403,6 +404,7 @@ native_start_all_aps(void)
>                     M_WAITOK | M_ZERO);
>                 dbg_stack = (char *)kmem_malloc(kernel_arena, PAGE_SIZE,
>                     M_WAITOK | M_ZERO);
> +printf("allocated dbg_stack: %p\n", dbg_stack);
>                 dpcpu = (void *)kmem_malloc(kernel_arena, DPCPU_SIZE,
>                     M_WAITOK | M_ZERO);
>

I applied your patch. The boot stops at the same spot. Also, I can't see
any of the two print messages added in the patch. I booted from a Live CD
to look at the logs, but they are not stored. I checked dmesg.boot and
messages, and /var/log/xen/ none of them have the logs. They all have logs
of the previous boot.

This is all what I can see from my screen:

XEN) Scrubbing free RAM on 1 nodes using 4 CPUs
(XEN) [VT-D] DMAR: [DMA Read} Request device [0000:00:1a.0] fault addr
9ce13000. iommu reg - ffff82c000203000
(XEN) [VT-D] DMAR: reason 06 - PTE read access is not set
(XEN) ........... done
(XEN) initial low memory virq threshold set at 0x200 pages.
(XEN) Std. Loglevel: All
(XEN) Guest Loglevel: All
(XEN) Xen is keeping VGA console
(XEN) Boot video device 00:02.0
(XEN) ***Serial input -> DOM0 (type 'CTRL-a' three times to switch input to
Xen)
(XEN) Freed 320 kB init memory
FreeBSD PVH running on xen-3.0-x86_64p
Copyright (c) 1992-2018 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993,
1994 The regents of the University of California. All rights reserved.
FreeBSD is a registered trademark of The FreeBSD Foundation.
FreeBSD 12.0-CURRENT #0 r333974M: Wed May 11 37:05 IST 2018
    root at freebsd-test:/usr/obj/usr/src/amd64.amd64/sys/GENERIC amd64
WARNING: WITNESS option enabled, expect reduced performance.
VT(vga): text 80x25
CPU: Intel(R) Core(TM) i7-4710HQ CPU @ 2.50GHz (2494.22-MHz K8-class CPU)
    Origin="GenuineIntel" Id=0x306c3 Family=0x6 Model=0x3c Stepping=3
    Features=0x17c1cbf5<FPU,DE,TSC,MSR,PAE,MCE.CX8.APIC,SEP,
MCA,CMOV,PAT,ACPI,MMX
FXSR,SSE,SSE2,HTT>
    Features2=0xf6f83203<SSE3,PCLMULQDQ,SSSE3,FMA,CX16,SSE4.
1,SSE4.2,x2APIC,MOVBE
POPCNT,AESNI,XSAVE,AVX,F16C,RDRAND,HV>
    AMD Features=0x20101800<SYSCALL,<s12>NX,LM>
    AMD Features2=0x21<<LAHF,ABM>
    Structured Extended Features=0x2329<FSGSBASE,BMI1,AVX2,BMI2,ERMS,NFPUSG>
Hypervisor: Origin = "XenVMMXenVMM"
real memory  = 5982789632 (5705 MB)
avail memory = 4051214336 (3863 MB)
(XEN) d0v1 Triple fault - invoking HVM shutdown action 0
(XEN) *** Dumping Dom0 vcpu#1 state: ***
(XEN) ----[ Xen-4.7.2 x86_64 debug=n Not tainted ]----
(XEN) CPU:    1
(XEN) RIP:    0020:[<ffffffff80b52fbe>]
(XEN) RFLAGS:  0000000000010046    CONTEXT: hvm guest (d0v1)
(XEN) rax: 0000000000000000   rbx: fffff801649a1ff8   rcx: 00000000000000c7
(XEN) rdx: ffffffff81b166f0   rsi: 0000000000000000   rdi: fffff801649a1ff8
(XEN) rbp: fffffe00027e8bb0   rsp: fffffe0027e8b80   r8: fefefefefefefeff
(XEN) r15: ffffffff812f497c   cr0: 0000000000000011   cr4: 0000000000000020
(XEN) cr3: 0000000002e36000   cr2: 0000000000000000
(XEN) ds: 0028   es: 0028   fs: 0028   gs: 0028   ss: 0028   cs: 0020
(XEN) Guest stack trace from rsp=fffffe00009fffa0:
(XEN)   Fault while accessing guest memory.
(XEN) Hardware Dom0 halted: halting machine


When I run addr2line on ffffffff80b52fbe, I get:
./machine/pcpu.h:231

-- 
Regards,
Pratyush Yadav