Re: [PATCH 1/3] gpex-acpi: Support PCI link devices outside the host bridge

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

On Tue, May 28, 2024 at 01:01:01PM +0530, Sunil V L wrote:
> Currently, PCI link devices (PNP0C0F) are always created within the
> scope of the PCI root complex. However, RISC-V needs PCI link devices to
> be outside the scope of the PCI host bridge to properly enable the probe
> order. This matches the example given in the ACPI specification section
> 6.2.13.1 as well.

Given that, what happens if we do this for all architectures?

> 
> Enable creating link devices outside the scope of PCI root complex based
> on the flag which gets set currently only for RISC-V.
> 
> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> ---
>  hw/pci-host/gpex-acpi.c    | 29 ++++++++++++++++++++++++-----
>  hw/riscv/virt-acpi-build.c |  8 +++++---
>  include/hw/pci-host/gpex.h |  5 ++++-
>  3 files changed, 33 insertions(+), 9 deletions(-)
> 
> diff --git a/hw/pci-host/gpex-acpi.c b/hw/pci-host/gpex-acpi.c
> index f69413ea2c..cea89a3ed8 100644
> --- a/hw/pci-host/gpex-acpi.c
> +++ b/hw/pci-host/gpex-acpi.c
> @@ -7,7 +7,7 @@
>  #include "hw/pci/pcie_host.h"
>  #include "hw/acpi/cxl.h"
>  
> -static void acpi_dsdt_add_pci_route_table(Aml *dev, uint32_t irq)
> +static void acpi_dsdt_add_pci_route_table(Aml *scope, Aml *dev, uint32_t irq)
>  {
>      Aml *method, *crs;
>      int i, slot_no;
> @@ -45,7 +45,17 @@ static void acpi_dsdt_add_pci_route_table(Aml *dev, uint32_t irq)
>          aml_append(dev_gsi, aml_name_decl("_CRS", crs));
>          method = aml_method("_SRS", 1, AML_NOTSERIALIZED);
>          aml_append(dev_gsi, method);
> -        aml_append(dev, dev_gsi);
> +
> +        /*
> +         * Some architectures like RISC-V


Just risc-v for now right?
> need PCI link devices created
> +         * outside the scope of the PCI host bridge

.. in order to load the drivers in the correct order.
Others .... .

> similar to the example
> +         * given in the section 6.2.13.1 of ACPI spec 6.5.


This is not how we quote ACPI spec.

First you find the earliest spec version which has it.
Then you mention that, section/table # and title.
For example:

	ACPI 6.1: 18.3.2.8 Generic Hardware Error Source


> +         */
> +         if (scope) {
> +            aml_append(scope, dev_gsi);
> +        } else {
> +            aml_append(dev, dev_gsi);
> +        }
>      }
>  }
>  
> @@ -174,7 +184,11 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
>                  aml_append(dev, aml_name_decl("_PXM", aml_int(numa_node)));
>              }
>  
> -            acpi_dsdt_add_pci_route_table(dev, cfg->irq);
> +            if (cfg->flags & GPEX_FLAGS_EXT_GSI_LINK) {
> +                acpi_dsdt_add_pci_route_table(scope, dev, cfg->irq);
> +            } else {
> +                acpi_dsdt_add_pci_route_table(NULL, dev, cfg->irq);
> +            }
>  
>              /*
>               * Resources defined for PXBs are composed of the following parts:
> @@ -205,7 +219,11 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
>      aml_append(dev, aml_name_decl("_STR", aml_unicode("PCIe 0 Device")));
>      aml_append(dev, aml_name_decl("_CCA", aml_int(1)));
>  
> -    acpi_dsdt_add_pci_route_table(dev, cfg->irq);
> +    if (cfg->flags & GPEX_FLAGS_EXT_GSI_LINK) {
> +        acpi_dsdt_add_pci_route_table(scope, dev, cfg->irq);
> +    } else {
> +        acpi_dsdt_add_pci_route_table(NULL, dev, cfg->irq);
> +    }
>  
>      method = aml_method("_CBA", 0, AML_NOTSERIALIZED);
>      aml_append(method, aml_return(aml_int(cfg->ecam.base)));
> @@ -282,7 +300,7 @@ void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg)
>      crs_range_set_free(&crs_range_set);
>  }
>  
> -void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq)
> +void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq, uint32_t flags)
>  {
>      bool ambig;
>      Object *obj = object_resolve_path_type("", TYPE_GPEX_HOST, &ambig);
> @@ -292,5 +310,6 @@ void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq)
>      }
>  
>      GPEX_HOST(obj)->gpex_cfg.irq = irq;
> +    GPEX_HOST(obj)->gpex_cfg.flags = flags;
>      acpi_dsdt_add_gpex(scope, &GPEX_HOST(obj)->gpex_cfg);
>  }
> diff --git a/hw/riscv/virt-acpi-build.c b/hw/riscv/virt-acpi-build.c
> index 0925528160..832a3acb8d 100644
> --- a/hw/riscv/virt-acpi-build.c
> +++ b/hw/riscv/virt-acpi-build.c
> @@ -417,19 +417,21 @@ static void build_dsdt(GArray *table_data,
>          virtio_acpi_dsdt_add(scope, memmap[VIRT_VIRTIO].base,
>                               memmap[VIRT_VIRTIO].size,
>                               VIRTIO_IRQ, 0, VIRTIO_COUNT);
> -        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ);
> +        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ, GPEX_FLAGS_EXT_GSI_LINK);
>      } else if (socket_count == 2) {
>          virtio_acpi_dsdt_add(scope, memmap[VIRT_VIRTIO].base,
>                               memmap[VIRT_VIRTIO].size,
>                               VIRTIO_IRQ + VIRT_IRQCHIP_NUM_SOURCES, 0,
>                               VIRTIO_COUNT);
> -        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES);
> +        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES,
> +                                GPEX_FLAGS_EXT_GSI_LINK);
>      } else {
>          virtio_acpi_dsdt_add(scope, memmap[VIRT_VIRTIO].base,
>                               memmap[VIRT_VIRTIO].size,
>                               VIRTIO_IRQ + VIRT_IRQCHIP_NUM_SOURCES, 0,
>                               VIRTIO_COUNT);
> -        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES * 2);
> +        acpi_dsdt_add_gpex_host(scope, PCIE_IRQ + VIRT_IRQCHIP_NUM_SOURCES * 2,
> +                                GPEX_FLAGS_EXT_GSI_LINK);
>      }
>  
>      aml_append(dsdt, scope);
> diff --git a/include/hw/pci-host/gpex.h b/include/hw/pci-host/gpex.h
> index dce883573b..bee17d62c5 100644
> --- a/include/hw/pci-host/gpex.h
> +++ b/include/hw/pci-host/gpex.h
> @@ -47,8 +47,11 @@ struct GPEXConfig {
>      MemMapEntry pio;
>      int         irq;
>      PCIBus      *bus;
> +    uint32_t    flags;
>  };
>  
> +#define GPEX_FLAGS_EXT_GSI_LINK BIT(0)
> +
>  struct GPEXHost {
>      /*< private >*/
>      PCIExpressHost parent_obj;
> @@ -71,7 +74,7 @@ struct GPEXHost {
>  int gpex_set_irq_num(GPEXHost *s, int index, int gsi);
>  
>  void acpi_dsdt_add_gpex(Aml *scope, struct GPEXConfig *cfg);
> -void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq);
> +void acpi_dsdt_add_gpex_host(Aml *scope, uint32_t irq, uint32_t flags);
>  
>  #define PCI_HOST_PIO_BASE               "x-pio-base"
>  #define PCI_HOST_PIO_SIZE               "x-pio-size"
> -- 
> 2.40.1
> 
>