Re: [v2 1/1] hw/i386/acpi-build: add OSHP method support for SHPC driver load

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 28 Jun 2024 03:04:28 +0000
"Gao,Shiyuan" <gaoshiyuan@baidu.com> wrote:

> > > that OS cannot get control of SHPC hotplug and hotplug device to
> > > the PCI bridge will fail when we use SHPC Native type:
> > >
> > >   [3.336059] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via OSHP (\_SB_.PCI0.S28_)
> > >   [3.337408] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via OSHP (\_SB_.PCI0)
> > >   [3.338710] shpchp 0000:00:03.0: Cannot get control of SHPC hotplug
> > >
> > > Add OSHP method support for transfer control to the operating system,
> > > after this SHPC driver will be loaded success and the hotplug device to
> > > the PCI bridge will success when we use SHPC Native type.
> > >
> > >   [1.703975] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via OSHP (\_SB_.PCI0.S18_)
> > >   [1.704934] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via OSHP (\_SB_.PCI0)
> > >   [1.705855] shpchp 0000:00:03.0: Gained control of SHPC hotplug (\_SB_.PCI0)
> > >   [1.707054] shpchp 0000:00:03.0: HPC vendor_id 1b36 device_id 1 ss_vid 0 ss_did 0  
> >
> > please describe in commit message reproducer
> > (aka QEMU CLI and guest OS and if necessary other details)  
> 
> qemu-system-x86_64 -machine pc-q35-9.0
>     ...
>     -global PIIX4_PM.acpi-pci-hotplug-with-bridge-support=off

please use full QEMU CLI and follow up steps to trigger the issue.

From above it's not obvious what and where you are trying to hotplug
 
> guest OS: centos7/ubuntu22.04
> 
> I will add it in the next version.
> 
> > > +/*
> > > + * PCI Firmware Specification 3.0
> > > + * 4.8. The OSHP Control Method
> > > + */
> > > +static Aml *build_oshp_method(void)
> > > +{
> > > +    Aml *method;
> > > +
> > > +    /*
> > > +     * We don't use ACPI to control the SHPC, so just return
> > > +     * success is enough.
> > > +     */
> > > +    method = aml_method("OSHP", 0, AML_NOTSERIALIZED);
> > > +    aml_append(method, aml_return(aml_int(0x0)));
> > > +    return method;
> > > +}
> > > +
> > >  static void
> > >  build_dsdt(GArray *table_data, BIOSLinker *linker,
> > >             AcpiPmInfo *pm, AcpiMiscInfo *misc,
> > > @@ -1452,6 +1469,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> > >          aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03")));
> > >          aml_append(dev, aml_name_decl("_UID", aml_int(pcmc->pci_root_uid)));
> > >          aml_append(dev, aml_pci_edsm());
> > > +        aml_append(dev, build_oshp_method());  
> >
> > it's global and what will happen if we have ACPI PCI hotplug enabled
> > and guest calls this NOP method?  
> 
> ths OS get the control of SHPC hotplug and SHPC driver load fail later.
> 
> [    6.170345] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via OSHP (\_SB_.PCI0.S18_)
> [    6.171962] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via OSHP (\_SB_.PCI0)
> [    6.173556] shpchp 0000:00:03.0: Gained control of SHPC hotplug (\_SB_.PCI0)
> [    6.175144] shpchp 0000:00:03.0: HPC vendor_id 1b36 device_id 1 ss_vid 0 ss_did 0
> [    6.196153] shpchp 0000:00:03.0: irq 24 for MSI/MSI-X
> [    6.197211] shpchp 0000:00:03.0: pci_hp_register failed with error -16
> [    6.198272] shpchp 0000:00:03.0: Slot initialization failed
> 
> this looks more suitable.
> 
> +    if (!pm->pcihp_bridge_en) {
> +        aml_append(dev, build_i440fx_oshp_method());
> +    }

we also have
 PIIX4_PM.acpi-root-pci-hotplug (default true)
though it seems that ACPI hotplug takes precedence of SHPC if both are enabled.
So I'd take it and OSHP approach seems simpler than adding _OSC to do the same.

> 
> >  
> > >          aml_append(sb_scope, dev);
> > >          aml_append(dsdt, sb_scope);
> > >
> > > @@ -1586,6 +1604,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker,
> > >                  aml_append(dev, build_q35_osc_method(true));
> > >              } else {
> > >                  aml_append(dev, aml_name_decl("_HID", aml_eisaid("PNP0A03")));
> > > +                aml_append(dev, build_oshp_method());
> > >              }
> > >
> > >              if (numa_node != NUMA_NODE_UNASSIGNED) {  
> 
> Hot plug/unplug a device using SHPC will take more time than ACPI PCI hotplug, because
> after pressing the button, it can be cancelled within 5 seconds in SHPC driver. 

for SHPC on PXB see,
commit d10dda2d60 hw/pci-bridge: disable SHPC in PXB

it seems that enabling SHPC on PXB in QEMU is not enough,
UEFI needs to support that as well
(CCing Gerd to check whether it is possible at all) 

> If I want to use ACPI PCI hotplug in the pxb bridge, what else need to be done?

does it have to be hotplug directly into pxb or
would be it be sufficient to have hotplug support
on pci-bridge attached to a pxb?

I particularly do not like spreading ACPI hotplug 
to any host bridges, as it's quite complicated
code.

Michael,
Are there any reasons why we don't have hotplug directly
on PXBs enabled from PCI spec point of view?
(Is it that host bridges just do not support hotplug into them?)



> thanks.
>