[libvirt] [PATCH] qemu: Support chardevs with ARM virt machines

[Andrew Jones]

On Sun, 2017-06-25 at 13:46 +0200, Christoffer Dall wrote:
>>On Sun, Jun 25, 2017 at 4:07 AM, Andrea Bolognani <abologna redhat com> wrote:
>> On Sat, 2017-06-24 at 16:07 +0200, Christoffer Dall wrote:
>>> > The way I see it, the bug is about libvirt being unable to
>>> > launch guests which use the <console><log> feature, and with
>>> > that in mind your patch is correct but doesn't solve the
>>> > issue, because even thought that specific error is gone you
>>> > immediately run into a different one and your guest is still
>>> > unable to start.
>>>
>>> I didn't experience this, it was actually working on my end.  I wonder
>>> if it's related to the QEMU version, where I seem to remember we
>>> changed what some serial options turned into.  But I for sure did not
>>> see "-device isa-serial..." on the command line, so maybe not.
>>
>> That's very different from the behavior I'm seeing, and I
>> can't figure out why that would be the case. That's why
>> having your QEMU command line would be very useful.
>>
>> As for differences in QEMU binaries, there might be some
>> capability that I haven't considered and influences the
>> generated command line. I'll look into that.
>
>Cool,  I'll have a look as well and will document my complete
>environment, then hopefully we can diff with yours and see where this
>ISA thing shows up.

It's likely a pci-serial vs. isa-serial device getting created. Something
like

  -device pcie-root-port,port=0xa,chassis=3,id=pci.3,bus=pcie.0,addr=0x1.0x2 \
  -chardev stdio,logfile=logfile,id=chardev0,logappend=off \
  -device pci-serial,chardev=chardev0,bus=pci.3,addr=0x0

works for me, but only with upstream (not RHEL) qemu, and when adding
console=ttyS0 to the guest kernel command line.

So far we haven't wanted the pci-serial device in AArch64 RHEL qemu, as
we didn't see a need for it. Is there any reason it should be supported
other than it allows the logfile feature to work? As Andrea pointed out,
in [1], I wrote that I think the logfile feature should work even with
the default PL011 serial console.

Thanks,
drew

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1456882#c4