Re: [PATCH 2/2] acpi: x86: pcihp: add support hotplug on multifunction bridges

[Daniel P . Berrangé]

On Thu, Jul 22, 2021 at 01:49:34PM -0400, Michael S. Tsirkin wrote:
> On Thu, Jul 22, 2021 at 06:59:45AM -0400, Igor Mammedov wrote:
> > Commit 17858a1695 (hw/acpi/ich9: Set ACPI PCI hot-plug as default on Q35)
> > switched PCI hotplug from native to ACPI one by default.
> > 
> > That however breaks ihotplug on following CLI that used to work:
> 
> s/ihotplug/hotplug/ ?
> 
> >    -nodefaults -machine q35 \
> >    -device 
> > pcie-root-port,id=pcie-root-port-0,multifunction=on,bus=pcie.0,addr=0x1,chassis=1
> >  \
> >    -device 
> > pcie-root-port,id=pcie-root-port-1,port=0x1,addr=0x1.0x1,bus=pcie.0,chassis=2
> > 
> > where PCI device is hotplugged to pcie-root-port-1 with error on guest side:
> > 
> >   ACPI BIOS Error (bug): Could not resolve symbol [^S0B.PCNT], AE_NOT_FOUND 
> > (20201113/psargs-330)
> >   ACPI Error: Aborting method \_SB.PCI0.PCNT due to previous error 
> > (AE_NOT_FOUND) (20201113/psparse-531)
> >   ACPI Error: Aborting method \_GPE._E01 due to previous error 
> > (AE_NOT_FOUND) (20201113/psparse-531)
> >   ACPI Error: AE_NOT_FOUND, while evaluating GPE method [_E01] 
> > (20201113/evgpe-515)
> > 
> > cause is that QEMU's ACPI hotplug never supported functions other then 0
> > and due to bug it was generating notification entries for not described
> > functions.
> > 
> > Technically there is no reason not to describe cold-plugged bridges
> > (root ports) on functions other then 0, as they similaraly to bridge
> > on function 0 are unpluggable.
> > 
> > Fix consists of describing cold-plugged bridges[root ports] on functions
> > other than 0.
> 
> 
> I would add: since we need to describe multifunction devices
> 
> 
> > 
> > Fixes: 17858a169508609ca9063c544833e5a1adeb7b52
> 
> use short hash and include subject within ("subject here") please

Using short hashes isn't a good idea in commits IMHO. A git short
hash is only guaranteed unique at the time it is generated. In future
the repo might gain commits that result in a clashing short hash.
Using the full hash is good.


Regards,
Daniel
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