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

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jul 23, 2021 at 09:47:26AM +0200, Igor Mammedov wrote:
> On Thu, 22 Jul 2021 13:49:34 -0400
> "Michael S. Tsirkin" <mst@redhat.com> 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
> 
> ok
> 
> > 
> > > 
> > > Fixes: 17858a169508609ca9063c544833e5a1adeb7b52  
> > 
> > use short hash and include subject within ("subject here") please
> > 
> > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > Reported-by: Laurent Vivier <lvivier@redhat.com>
> > > ---
> > >  hw/i386/acpi-build.c | 31 ++++++++++++++++++++++++-------
> > >  1 file changed, 24 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > index b40e284b72..77cb7a338a 100644
> > > --- a/hw/i386/acpi-build.c
> > > +++ b/hw/i386/acpi-build.c
> > > @@ -364,7 +364,7 @@ static void build_append_pcihp_notify_entry(Aml *method, int slot)
> > >      int32_t devfn = PCI_DEVFN(slot, 0);
> > >  
> > >      if_ctx = aml_if(aml_and(aml_arg(0), aml_int(0x1U << slot), NULL));
> > > -    aml_append(if_ctx, aml_notify(aml_name("S%.02X", devfn), aml_arg(1)));
> > > +    aml_append(if_ctx, aml_notify(aml_name("^S%.03X", devfn), aml_arg(1)));
> > >      aml_append(method, if_ctx);
> > >  }
> > >  
> > 
> > why are you adding a parent prefix here? anything wrong with
> > relying on search rules?
> > Seems like an unrelated change.
> it's remnants from time I was trying to figure out
> why functions weren't visible, I'll drop it.
> 
>  
> > Also there's always 8 bit in devfn. Why do we need an extra 0?
> 2 digits hold slot value, like it used to be and
> the last one to hold function. Basically like it's shown in PCI.FW spec example.
> 
> but if you prefer to print raw devfn I can change to that,
> it should work as well.

will make the patch smaller, won't it? we can always change it
separately to match spec examples more closely.

> > > @@ -389,18 +389,26 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
> > >          PCIDeviceClass *pc;
> > >          PCIDevice *pdev = bus->devices[devfn];
> > >          int slot = PCI_SLOT(devfn);
> > > +        int func = PCI_FUNC(devfn);
> > > +        /* ACPI spec: 1.0b: Table 6-2 _ADR Object Bus Types, PCI type */
> > > +        int adr = slot << 16 | func;
> > >          bool hotplug_enabled_dev;
> > >          bool bridge_in_acpi;
> > >          bool cold_plugged_bridge;
> > >  
> > >          if (!pdev) {
> > > -            if (bsel) { /* add hotplug slots for non present devices */
> > > +            /*
> > > +             * add hotplug slots for non present devices.
> > > +             * hotplug is supported only for non-multifunction device
> > > +             * so generate device description only for function 0
> > > +             */
> > > +            if (bsel && !PCI_FUNC(devfn)) {  
> > 
> > replace with func here and elsewhere?
> 
> ok
> 
> > 
> > >                  if (pci_bus_is_express(bus) && slot > 0) {
> > >                      break;
> > >                  }
> > > -                dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
> > > +                dev = aml_device("S%.03X", devfn);
> > >                  aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
> > > -                aml_append(dev, aml_name_decl("_ADR", aml_int(slot << 16)));
> > > +                aml_append(dev, aml_name_decl("_ADR", aml_int(adr)));
> > >                  method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
> > >                  aml_append(method,
> > >                      aml_call2("PCEJ", aml_name("BSEL"), aml_name("_SUN"))
> > > @@ -436,9 +444,18 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
> > >              continue;
> > >          }
> > >  
> > > +        /*
> > > +         * allow describing coldplugged bridges in ACPI even if they are not
> > > +         * on function 0, as they are not unpluggale, for all other devices  
> > 
> > 
> > unpluggable 
> > 
> > > +         * generate description only for function 0 per slot
> > > +         */
> > > +        if (PCI_FUNC(devfn) && !bridge_in_acpi) {
> > > +            continue;
> > > +        }
> > > +
> > >          /* start to compose PCI slot descriptor */
> > > -        dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
> > > -        aml_append(dev, aml_name_decl("_ADR", aml_int(slot << 16)));
> > > +        dev = aml_device("S%.03X", devfn);
> > > +        aml_append(dev, aml_name_decl("_ADR", aml_int(adr)));
> > >  
> > >          if (bsel) {
> > >              /*
> > > @@ -529,7 +546,7 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
> > >                      continue;
> > >                  }
> > >  
> > > -                aml_append(method, aml_name("^S%.02X.PCNT",
> > > +                aml_append(method, aml_name("^S%.03X.PCNT",
> > >                                              sec->parent_dev->devfn));
> > >              }
> > >          }
> > > -- 
> > > 2.27.0  
> >