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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 23 Feb 2016 08:07:17 +0100
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Subject: Re: [Qemu-devel] [PATCH RFC] fw-cfg: support writeable blobs
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>, Xiao Guangrong <guangrong.xiao@linux.intel.com>, Eduardo Habkost <ehabkost@redhat.com>, Igor Mammedov <imammedo@redhat.com>, "Gabriel L. Somlo" <somlo@cmu.edu>, qemu-devel@nongnu.org, Michael Walle <michael@walle.cc>, Kevin O'Connor <kevin@koconnor.net>, qemu-arm@nongnu.org, Shannon Zhao <zhaoshenglong@huawei.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>

On Mo, 2016-02-22 at 22:12 +0200, Michael S. Tsirkin wrote:
> On Mon, Feb 22, 2016 at 03:26:56PM +0100, Gerd Hoffmann wrote:
> > On Mo, 2016-02-22 at 14:41 +0200, Michael S. Tsirkin wrote:
> > > Useful to send guest data back to QEMU.
> >=20
> > Use case?
> >=20
> > cheers,
> >   Gerd
>=20
> VM GEN ID at least wants to pass address of some blob
> in guest memory to host.
>=20
> Apparently, that's also useful for nvdimm.
>=20
> A reasonable way to do that seems to be to write it into
> fw cfg file, this way it's also migrated automatically.

Both seem to be about acpi aml code talking to qemu backend.

Not sure fw_cfg files are reasonable for that, given that you have to
fetch the directory listing, parse it to figure the entry index, ...

I want see a patch actually using that before going to merge it.

cheers,
  Gerd