panic: pmap active 0xfffff8001b7154b8

[Bryan Drewery]

On 5/7/2015 7:08 AM, Johan Schuijt-Li wrote:
> Hi,
> 
> We’ve been seeing (seemingly) random reboots on 10.1-RELEASE virtual machines (KVM virtualisation) on our production servers. In an attempt to determine what was causing this we’ve switched to running a kernel with INVARIANTS enabled. This resulted for us in the following panic:
> 
> Unread portion of the kernel message buffer:
> panic: pmap active 0xfffff8001b7154b8
> cpuid = 3
> KDB: stack backtrace:
> db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe03dd1493a0
> kdb_backtrace() at kdb_backtrace+0x39/frame 0xfffffe03dd149450
> vpanic() at vpanic+0x126/frame 0xfffffe03dd149490
> kassert_panic() at kassert_panic+0x139/frame 0xfffffe03dd149500
> pmap_remove_pages() at pmap_remove_pages+0x8c/frame 0xfffffe03dd1495f0
> exec_new_vmspace() at exec_new_vmspace+0x16a/frame 0xfffffe03dd149650
> exec_elf64_imgact() at exec_elf64_imgact+0x658/frame 0xfffffe03dd149720
> kern_execve() at kern_execve+0x5e4/frame 0xfffffe03dd149a80
> sys_execve() at sys_execve+0x37/frame 0xfffffe03dd149ae0
> amd64_syscall() at amd64_syscall+0x25a/frame 0xfffffe03dd149bf0
> Xfast_syscall() at Xfast_syscall+0xfb/frame 0xfffffe03dd149bf0
> --- syscall (59, FreeBSD ELF64, sys_execve), rip = 0x80158af1a, rsp = 0x7fffffffac38, rbp = 0x7fffffffad40 ---
> 
> 
> I’ve only come across one other report here (without result unfortunate):
> https://lists.freebsd.org/pipermail/freebsd-current/2014-June/050827.html <https://lists.freebsd.org/pipermail/freebsd-current/2014-June/050827.html>
> 

I looked around for the conclusion of that thread but could not find it.
I was reproducing so often I'm sure this case was fixed. I may have
privately contacted one of the VM maintainers to fix it. However lacking
evidence I think it just stopped happening for me and I never reported
anything useful.

> Are other people aware of this issue or working on this?
> 
> I can provide access to a VM with a kernel dump and the kernel build for extra information if needed.
> 

What we really need is a full core dump (minidump) and backtrace. This
will let us inspect the pmap state.

https://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug.html
https://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug-gdb.html


-- 
Regards,
Bryan Drewery

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