Re: [libvirt] [PATCH] qemu: Support chardevs with ARM virt machines
On Fri, 2017-06-23 at 18:32 +0200, Christoffer Dall wrote:
> You mention in [1] that applying this patch and using a
> recent QEMU fixes the problem for you, however I can't
> say the same: I still get
>
> -device isa-serial,chardev=charserial0,id=serial0:
> No 'ISA' bus found for device 'isa-serial'
Well that's not the bug reported in 2777. If you try to create an ISA
bus or configure your domain with an ISA bus on AArch64 your are bound
to fail, because we never had, and we never will have, support for an
ISA bus on AArch64.
Sure, I'm aware of that.
To verify what this patch changes, you can use the test xml file
listed in [1] as well:
<domain type='kvm'>
<name>testlogfile</name>
<memory unit='KiB'>524288</memory>
<os>
<type arch='aarch64' machine='virt-2.7'>hvm</type>
</os>
<devices>
<serial type='pty'>
<log file='/tmp/testlogfile.log' append='off'/>
<target port='0'/>
</serial>
</devices>
</domain>
Or any working domain configuration where you add <log file='...' />
to the domain definition.
In both cases, I get the error reported in my previous
message.
You didn't really answer my question, though: can *you*
start such a guest succesfully using a patched libvirt?
And if so, what is the corresponding QEMU command line?
It may be that we have an additional bug in libvirt that it under
some
circumstances tries to create an ISA bus with an AArch64 VM, but I
don't see that being related to the patch above?
It's not.
Note that the submitted patch fixes virQEMUCapsSupportsChardev,
which
should be independent from any ISA bus fixes in libvirt, but given my
very limited experience with libvirt, I may be wrong here.
No, you're correct.
In summary, if your test setup goes from "error: unsupported
configuration: logfile not supported in this QEMU binary" to "-device
isa-serial,chardev=charserial0,id=serial0: No 'ISA' bus found for
device 'isa-serial'" then I'd argue that my patch solves the first
issue.
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.
Just to be clear: I'm not against this patch, we definitely
want to fix virQEMUCapsSupportsChardev(). What gave me pause
is simply the fact that you seemed to claim it made the
<console><log> feature usable, which I'm still unconvinced
is actually the case.
--
Andrea Bolognani / Red Hat / Virtualization