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Re: [Qemu-devel] PCI(e): Documentation "io-reserve" and related properti
From: |
Kashyap Chamarthy |
Subject: |
Re: [Qemu-devel] PCI(e): Documentation "io-reserve" and related properties? |
Date: |
Tue, 11 Jun 2019 09:21:00 +0200 |
User-agent: |
Mutt/1.11.3 (2019-02-01) |
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