Re: [Qemu-devel] PCI(e): Documentation "io-reserve" and related properties?

[Kashyap Chamarthy <kchamart@redhat.com>]

On Thu, Jun 06, 2019 at 02:20:18PM -0400, Michael S. Tsirkin wrote:
> On Thu, Jun 06, 2019 at 06:19:43PM +0200, Kashyap Chamarthy wrote:
> > Hi folks,
> > 
> > Today I learnt about some obscure PCIe-related properties, in context of
> > the adding PCIe root ports to a guest, namely:
> > 
> >     io-reserve
> >     mem-reserve
> >     bus-reserve
> >     pref32-reserve
> >     pref64-reserve
> > 
> > Unfortunately, the commit[*] that added them provided no documentation
> > whatsover.
> > 
> > In my scenario, I was specifically wondering about what does
> > "io-reserve" mean, in what context to use it, etc.  (But documentation
> > about other properties is also welcome.)
> > 
> > Anyone more well-versed in this area care to shed some light?
> > 
> > 
> > [*] 6755e618d0 (hw/pci: add PCI resource reserve capability to legacy
> >     PCI bridge, 2018-08-21)
> 
> So normally bios would reserve just enough io space to satisfy all
> devices behind a bridge. What if you intend to hotplug more devices?
> These properties allow you to ask bios to reserve extra space.

Thanks.  Would be useful to have them documented in the official QEMU
command-line documentation.  Otherwise, they will remain as arcane
properties that barely anyone knows about.

-- 
/kashyap