Re: [PATCH v2] hw/uefi: add "info ovmf-log" + "query-ovmf-log" monitor commands

["Dr. David Alan Gilbert" <dave@treblig.org>]

* Daniel P. Berrangé (berrange@redhat.com) wrote:
> On Thu, Oct 09, 2025 at 01:56:09AM +0000, Dr. David Alan Gilbert wrote:
> > * Gerd Hoffmann (kraxel@redhat.com) wrote:
> > > Starting with the edk2-stable202508 tag OVMF (and ArmVirt too) have
> > > optional support for logging to a memory buffer.  There is guest side
> > > support -- for example in linux kernels v6.17+ -- to read that buffer.
> > > But that might not helpful if your guest stops booting early enough that
> > > guest tooling can not be used yet.  So host side support to read that
> > > log buffer is a useful thing to have.
> > > 
> > > This patch implements both qmp and hmp monitor commands to read the
> > > firmware log.
> > > 
> > > Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> > 
> > I'm OK with that, but I wonder if it would be better to have a command
> > that wrote the buffer to a file rather than displaying it directly; I don't
> > think we normally have anything else which outputs that much raw guest
> > provided data directly.
> > I assume when it goes wrong you end up with random unprintable junk in
> > the buffer.
> 
> 128 KB is on the high side, but is not terrible. Libvirt (arbitrarily)
> caps a QMP reply at 10 MB. Libvirt is going to want to send this on to
> the client app and will likely do that streaming in memory, so having
> it iin a file is not required from our POV.
> 
> IIRC, some of the query-block command replies can get insanely huge
> when the qcow2 chain is very long.

OK, what about sanitisation - if that text contains random binary what happens,
or should we make sure it's sanitised?

Dave

> With regards,
> Daniel
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