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
