Re: [Qemu-devel] [PATCH] q35/mch: implement extended TSEG sizes

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Jun 15, 2017 at 09:07:45AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > To be specific, what I meant is a bit that tells guest that a
> > config space register is available, and lets host find out
> > that guest is going to use it.
> > 
> > This to ensure full forward and backward compatibility.
> > 
> > I agree a fw cfg file for a single bit seems like an overkill, that's
> > why I thought sharing feature files with SMI would be a good idea.
> > 
> > Do you see an issue with that?
> 
> The point of placing the extended-tseg-size register in mch pci config
> is that the firmware can figure this easily *without* looking somewhere
> else, as all the other tseg (and smram) config bits are in mch pci
> config space too.
> 
> When involving fw_cfg there is no reason to keep the extended-tseg-size 
> register in mch.  We can simply place a "etc/q35-extended-tseg-size"
> file in fw_cfg then (which is either not present or contains the
> extended tseg size).  So a feature bit in fw_cfg looks absolutely
> pointless to me.
> 
> I still think the approach and patch by Laszlo is perfectly fine. 
> While being at it:
> 
> Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
> 
> cheers,
>   Gerd


I guess I'll merge it and we'll see if there's any fallout.
Thanks everyone.

-- 
MST