Re: [PATCH 0/4] ICH9 root PCI hotplug

[Michael S. Tsirkin]

On Wed, Nov 29, 2023 at 09:47:13AM +0000, Thierry Escande wrote:
> On 24/11/2023 15:54, Michael S. Tsirkin wrote:
> > On Fri, Nov 24, 2023 at 03:01:35PM +0100, Igor Mammedov wrote:
> > > On Wed, 15 Nov 2023 17:18:53 +0000
> > > Thierry Escande <thierry.escande@vates.tech> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > This series fixes acpi_hotplug_bridge accessor names, adds new accessors
> > > > for acpi-root-pci-hotplug property, and enables root PCI hotplug by
> > > > default for Q35 machine.
> > > 
> > > hotplug on Q35 hostbridge is not implemented intentionally
> > > to keep machine close to the real world.
> > 
> > > PCIe spec 3.1a, 1.3.2.3. Root Complex Integrated Endpoint Rules
> > > "
> > > A Root Complex Integrated Endpoint may not be hot-plugged independent of 
> > > the Root
> > > Complex as a whole.
> > > "
> > > )
> > 
> > To be more precise close to native hotplug.
> > But we used ACPI for several years now and it seems to be fine.
> > Maybe it's time we lifted the limitation?
> 
> And for what it's worth, lifting this limitation would allow PCIe devices
> passthrough on Q35 VMs with Xen as such devices are hotplugged.


More motivation in the commit log would be a good idea here.

> > 
> > 
> > > 
> > > PS:
> > > but patch 1/4 is good cleanup, pls include Reviewed-by's and resend it
> > > as a separate patch after 8.2 has been released (so it wouldn't get lost 
> > > in the traffic).
> > > 
> > > > 
> > > > Thierry Escande (4):
> > > >    ich9: Remove unused hotplug field from ICH9LPCPMRegs struct
> > > >    ich9: Renamed use_acpi_hotplug_bridge accessors
> > > >    ich9: Add accessors for acpi-root-pci-hotplug
> > > >    ich9: Enable root PCI hotplug by default
> > > > 
> > > >   hw/acpi/ich9.c         | 23 +++++++++++++++++++++--
> > > >   include/hw/acpi/ich9.h |  1 -
> > > >   2 files changed, 21 insertions(+), 3 deletions(-)
> > > > 
> >