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

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

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

> 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.

Also there's always 8 bit in devfn. Why do we need an extra 0?

  
> @@ -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?

>                  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