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

[Michael S. Tsirkin]

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.

> -- 
> /kashyap