On 6/11/19 10:21 AM, Kashyap Chamarthy wrote:
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.
There is some documentation under qemu/docs/pcie_pci_bridge.txt.
I agree there is always room for QEMU cmd-line improvement.
Thanks,
Marcel
