VirtIo errors inside VM with UFS-in-zvol

[Nikolay Denev]

On Mon, Aug 25, 2014 at 8:50 PM, Peter Grehan <grehan at freebsd.org> wrote:
> Hi Marat,
>
>
>>>    vtbd0: hard error cmd=write 290-305
>>>
>> I would like to report the same problem. I'm using  10.0-RELEASE-p7 as a
>> host, and 9.3-RELEASE as a guest. VM is created using vmrc script, it
>> installed fine. But on attempt to create additional fs inside the vm,
>> newfs just silently fails without writing anything to disk.  file -s on
>> a filesystem reports just 'data', instead of the usual "Unix Fast File
>> system"
>
>
>  This issue is caused by the FreeBSD GEOM code tasting the zvol, parsing
> partition/slice tables, and marking sections read-only.
>
>  There is a fix for this by mav@ in r264145 in CURRENT, and MFC'd to
> 10-STABLE in r265678 (May 8). The fix will be in 10.1.
>
>  The zfs man page lists the new zvol property and sysctls that can be used
> to prevent GEOM testing.
>
> later,
>
> Peter.
>
>
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Thanks Peter,

That would be volmode=dev, correct?
Does it make sense for either the scripts (runvm.sh, vmrc, etc) or
bhyve itself print a warning in such case?

--Nikolay