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Date: Tue, 23 Feb 2016 11:09:26 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH RFC] fw-cfg: support writeable blobs
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To: Gerd Hoffmann <kraxel@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 Tue, Feb 23, 2016 at 08:07:17AM +0100, Gerd Hoffmann wrote:
> 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.
> > > 
> > > Use case?
> > > 
> > > cheers,
> > >   Gerd
> > 
> > VM GEN ID at least wants to pass address of some blob
> > in guest memory to host.
> > 
> > Apparently, that's also useful for nvdimm.
> > 
> > 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.

At least not for gen id - there will be a linker patch
to initialize that.

> 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

Absolutely, this makes sense.

-- 
MST