[Bug 211651] emulators/virtualbox-ose-kmod 5.0.26_1 with Linux guest crashes 12.0-CURRENT host when # of processors > 1

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=211651

            Bug ID: 211651
           Summary: emulators/virtualbox-ose-kmod 5.0.26_1 with Linux
                    guest crashes 12.0-CURRENT host when # of processors >
                    1
           Product: Ports & Packages
           Version: Latest
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: Individual Port(s)
          Assignee: vbox at FreeBSD.org
          Reporter: truckman at FreeBSD.org
             Flags: maintainer-feedback?(vbox at FreeBSD.org)
          Assignee: vbox at FreeBSD.org

If I attempt to start a Linux guest on a FreeBSD 12.0-CURRENT host I get a
kernel panic similar to:

panic: Unregistered use of FPU in kernel
cpuid = 3
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe085a31c030
vpanic() at vpanic+0x182/frame 0xfffffe085a31c0b0
kassert_panic() at kassert_panic+0x126/frame 0xfffffe085a31c120
trap() at trap+0x7ae/frame 0xfffffe085a31c330
calltrap() at calltrap+0x8/frame 0xfffffe085a31c330
--- trap 0x16, rip = 0xffffffff827273a9, rsp = 0xfffffe085a31c408, rbp =
0xfffff
e085a31c430 ---
null_bug_bypass() at 0xffffffff827273a9/frame 0xfffffe085a31c430
null_bug_bypass() at 0xffffffff826985c7/frame 0x3
KDB: enter: panic

if the VM is configured with more than one processor.  I've seen this with both
CentOS 7 and Ubuntu 12 guests.  The panic appears to occur near the start of
the guest kernel boot after grub has run.  It appears to happen shortly after
the kernel message about TSC calibration is printed.  The symbols printed by
DDB leading up to the trap appear to be somewhat arbitrary.  The location of
the trap seems to be aboe the topmost BSS section symbol in one of the (last?)
loaded .kmod.

The code at the location that triggers the trap is:
   0xffffffff8272739d:  nop
   0xffffffff8272739e:  nop
   0xffffffff8272739f:  nop
   0xffffffff827273a0:  mov    %rsi,%rdx
   0xffffffff827273a3:  shr    $0x20,%rdx
   0xffffffff827273a7:  mov    %esi,%eax
=> 0xffffffff827273a9:  xrstor (%rdi)
   0xffffffff827273ac:  retq   
   0xffffffff827273ad:  int3   
   0xffffffff827273ae:  int3   
   0xffffffff827273af:  int3   
   0xffffffff827273b0:  int3

It is called from here:
   0xffffffff82667489:  test   %eax,%eax
   0xffffffff8266748b:  jne    0xffffffff826674a1
   0xffffffff8266748d:  movq   $0x3,0x5238(%r15)
   0xffffffff82667498:  mov    %rbx,%rsi
   0xffffffff8266749b:  and    $0xfffffffffffffffc,%rsi
   0xffffffff8266749f:  je     0xffffffff826674ad
   0xffffffff826674a1:  mov    0x5240(%r15),%rdi
   0xffffffff826674a8:  callq  0xffffffff827273a0
=> 0xffffffff826674ad:  or     %rbx,0x5238(%r15)
   0xffffffff826674b4:  mov    %r14d,%eax
   0xffffffff826674b7:  add    $0x8,%rsp

kgdb (from ports) doesn't believe that either of these to any function.

The VMs where I first saw the problem were initially created with Virtualbox 4
and the paravirtualization setting is "Legacy", but I can reproduce this panic
after creating a new VM which uses the "Default" setting, increasing the number
of processors to 4, and booting the CentOS 7 install .iso.

The CPU info is:

CPU: AMD FX-8320E Eight-Core Processor               (3210.84-MHz K8-class CPU)
  Origin="AuthenticAMD"  Id=0x600f20  Family=0x15  Model=0x2  Stepping=0
 
Features=0x178bfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,C
MOV,PAT,PSE36,CLFLUSH,MMX,FXSR,SSE,SSE2,HTT>
 
Features2=0x3e98320b<SSE3,PCLMULQDQ,MON,SSSE3,FMA,CX16,SSE4.1,SSE4.2,POPCNT,AE
SNI,XSAVE,OSXSAVE,AVX,F16C>
  AMD Features=0x2e500800<SYSCALL,NX,MMX+,FFXSR,Page1GB,RDTSCP,LM>
  AMD
Features2=0x1ebbfff<LAHF,CMP,SVM,ExtAPIC,CR8,ABM,SSE4A,MAS,Prefetch,OSVW,I
BS,XOP,SKINIT,WDT,LWP,FMA4,TCE,NodeId,TBM,Topology,PCXC,PNXC>
  Structured Extended Features=0x8<BMI1>
  SVM: NP,NRIP,VClean,AFlush,DAssist,NAsids=65536
  TSC: P-state invariant, performance statistics

Whether or not this problem occurs with Intel CPUs is unknown.

This problem did not occur before the upgrade from Virtualbox 4 to Virtualbox
5.

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