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

[Roger Pau Monné]

On Fri, May 18, 2018 at 05:29:06PM +0530, Pratyush Yadav wrote:
> Hi,
> 
> So I have been trying to get Xen to boot on my laptop. It is getting
> stuck with the following error messages:
> 
> (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 r333606: Mon May 14 19:59:08 UTC 2018
>     root at releng3.nyi.freebsd.org:/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  = 9991770112 (9528 MB)
> avail memory = 7936724992 (7569 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:[<ffffffff8102042b>]
> (XEN) RFLAGS:  0000000000010016    CONTEXT: hvm guest (d0v1)
> (XEN) rax: 0000000000000000   rbx: ffffffff8201c100   rcx: 0000000000000001
> (XEN) rdx: 0000000000003078   rsi: ffffffff81b992f8   rdi: fffffe0003bb6078
> (XEN) rbp: fffffe00009ffff0   rsp: fffffe00009fffa0   r8: 00000000ffffffff
> (XEN) r15: 0000000000000400   cr0: 0000000000000011   cr4: 0000000000000020
> (XEN) cr3: 00000000035a4000   cr2: 0000000000000ff0
> (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
> 
> Any idea why this is happening and how can I fix this?

Can you execute:

addr2line -e /usr/lib/debug/boot/kernel/kernel.debug ffffffff8102042b

This should print a file and line number that would help in order to
debug what's going on.

Since it seems like the crash is caused by a triple fault on an AP,
you can try to boot with dom0_max_vcpus=1 on the xen_cmdline, that
might prevent the panic from happening.

We need however to figure out what's going on and fix it.

Thanks, Roger.