Re: [PATCH v7 2/2] hw/acpi: Implement the SRAT GI affinity structure

[Jonathan Cameron via <qemu-arm@nongnu.org>]

On Fri, 23 Feb 2024 12:42:23 +0000
<ankita@nvidia.com> wrote:

> From: Ankit Agrawal <ankita@nvidia.com>
> 
> ACPI spec provides a scheme to associate "Generic Initiators" [1]
> (e.g. heterogeneous processors and accelerators, GPUs, and I/O devices with
> integrated compute or DMA engines GPUs) with Proximity Domains. This is
> achieved using Generic Initiator Affinity Structure in SRAT. During bootup,
> Linux kernel parse the ACPI SRAT to determine the PXM ids and create a NUMA
> node for each unique PXM ID encountered. Qemu currently do not implement
> these structures while building SRAT.
> 
> Add GI structures while building VM ACPI SRAT. The association between
> device and node are stored using acpi-generic-initiator object. Lookup
> presence of all such objects and use them to build these structures.
> 
> The structure needs a PCI device handle [2] that consists of the device BDF.
> The vfio-pci device corresponding to the acpi-generic-initiator object is
> located to determine the BDF.
> 
> [1] ACPI Spec 6.3, Section 5.2.16.6
> [2] ACPI Spec 6.3, Table 5.80
> 
> Signed-off-by: Ankit Agrawal <ankita@nvidia.com>
Hi Ankit,

As the code stands the use of a list seems overkill.

Otherwise looks good to me.  I need Generic Ports support for CXL
stuff so will copy your approach for that as it's ended up nice
and simple.

Jonathan

> ---
>  hw/acpi/acpi-generic-initiator.c         | 84 ++++++++++++++++++++++++
>  hw/arm/virt-acpi-build.c                 |  3 +
>  include/hw/acpi/acpi-generic-initiator.h | 26 ++++++++
>  3 files changed, 113 insertions(+)
> 
> diff --git a/hw/acpi/acpi-generic-initiator.c b/hw/acpi/acpi-generic-initiator.c
> index 1ade2f723f..d78382bc63 100644
> --- a/hw/acpi/acpi-generic-initiator.c
> +++ b/hw/acpi/acpi-generic-initiator.c
> @@ -68,3 +68,87 @@ static void acpi_generic_initiator_class_init(ObjectClass *oc, void *data)
>      object_class_property_add(oc, "node", "int", NULL,
>          acpi_generic_initiator_set_node, NULL, NULL);
>  }
> +
> +static int acpi_generic_initiator_list(Object *obj, void *opaque)
> +{
> +    GSList **list = opaque;
> +
> +    if (object_dynamic_cast(obj, TYPE_ACPI_GENERIC_INITIATOR)) {
> +        *list = g_slist_append(*list, ACPI_GENERIC_INITIATOR(obj));
> +    }
> +
> +    object_child_foreach(obj, acpi_generic_initiator_list, opaque);

See below.  There is a recursive helper that avoids need for this.

> +    return 0;
> +}
> +
> +/*
> + * Identify Generic Initiator objects and link them into the list which is
> + * returned to the caller.
> + *
> + * Note: it is the caller's responsibility to free the list to avoid
> + * memory leak.
> + */
> +static GSList *acpi_generic_initiator_get_list(void)
> +{
> +    GSList *list = NULL;
> +
> +    object_child_foreach(object_get_root(),
> +                         acpi_generic_initiator_list, &list);

I think you can use object_child_foreach_recursive() and skip the manual
calling above?

> +    return list;
> +}
> +
> +/*
> + * ACPI 6.3:
> + * Table 5-78 Generic Initiator Affinity Structure
> + */
> +static void
> +build_srat_generic_pci_initiator_affinity(GArray *table_data, int node,
> +                                          PCIDeviceHandle *handle)
> +{
> +    uint8_t index;
> +
> +    build_append_int_noprefix(table_data, 5, 1);  /* Type */
> +    build_append_int_noprefix(table_data, 32, 1); /* Length */
> +    build_append_int_noprefix(table_data, 0, 1);  /* Reserved */
> +    build_append_int_noprefix(table_data, 1, 1);  /* Device Handle Type: PCI */
> +    build_append_int_noprefix(table_data, node, 4);  /* Proximity Domain */
> +
> +    /* Device Handle - PCI */
> +    build_append_int_noprefix(table_data, handle->segment, 2);
> +    build_append_int_noprefix(table_data, handle->bdf, 2);
> +    for (index = 0; index < 12; index++) {
> +        build_append_int_noprefix(table_data, 0, 1);
> +    }
> +
> +    build_append_int_noprefix(table_data, GEN_AFFINITY_ENABLED, 4); /* Flags */
> +    build_append_int_noprefix(table_data, 0, 4);     /* Reserved */
> +}
> +
> +void build_srat_generic_pci_initiator(GArray *table_data)
> +{
> +    GSList *gi_list, *list = acpi_generic_initiator_get_list();


Did you consider just have the functional called in the scan do this?
Not sure you need anything as a parameter beyond the GArray *table_data

Something like...

static int acpi_generic_initiator_list(Object *obj, void *opaque)
{
    uint8_t index;
    AcpiGenericInitiator *gi;
    GArray *table_data = opaque;
    PCIDeviceHandle dev_handle;
    PCIDevice *pci_dev;
    Object *o;

    if (!object_dynamic_cast(obj, TYPE_ACPI_GENERIC_INITIATOR)) {
        return 0;
    }

    gi = ACPI_GENERIC_INITIATOR(obj);
    o = object_resolve_path_type(gi->pci_dev, TYPE_PCI_DEVICE, NULL);
    if (!o) {
	error_setg(&error_abort, "GI: Specified device must be a PCI device.\n")
	return 1;
    }
    pci_dev = PCI_DEVICE(o);

    dev_handle.segment = 0;
    dev_handle.bdf = PCI_BUILD_BDF(pci_bus_num(pci_get_bus(pci_dev)),
                                               pci_dev->devfn);
    build_srat_generic_pci_initiator_affinity(table_data,
                                              gi->node, &dev_handle);
}

+ a call to.
    object_child_foreach_recursive(object_get_root(),
                                   acpi_generic_srat, table_data);	

> +    AcpiGenericInitiator *gi;
> +
> +    for (gi_list = list; gi_list; gi_list = gi_list->next) {
> +        PCIDeviceHandle dev_handle;
> +        PCIDevice *pci_dev;
> +        Object *o;
> +
> +        gi = gi_list->data;
> +
> +        o = object_resolve_path_type(gi->pci_dev, TYPE_PCI_DEVICE, NULL);
> +        if (!o) {
> +            error_printf("Specified device must be a PCI device.\n");
as above, use an errp rather than exit(1);
> +            exit(1);
> +        }
> +        pci_dev = PCI_DEVICE(o);
> +
> +        dev_handle.segment = 0;
> +        dev_handle.bdf = PCI_BUILD_BDF(pci_bus_num(pci_get_bus(pci_dev)),
> +                                                   pci_dev->devfn);
> +        build_srat_generic_pci_initiator_affinity(table_data,
> +                                                  gi->node, &dev_handle);
Should we check for consistency of gi->node and
-numa node,id=X entries?

Maybe just check less than numa_state->num_nodes as that's the variable
used to walk the other structures when building srat.

> +    }
> +
> +    g_slist_free(list);
> +}
> diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
> index 8bc35a483c..00d77327e0 100644
> --- a/hw/arm/virt-acpi-build.c
> +++ b/hw/arm/virt-acpi-build.c
> @@ -58,6 +58,7 @@
>  #include "migration/vmstate.h"
>  #include "hw/acpi/ghes.h"
>  #include "hw/acpi/viot.h"
> +#include "hw/acpi/acpi-generic-initiator.h"
>  
>  #define ARM_SPI_BASE 32
>  
> @@ -558,6 +559,8 @@ build_srat(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms)
>          }
>      }
>  
> +    build_srat_generic_pci_initiator(table_data);
Perhaps passing in a suitable Error ** would be sensible.

> +
>      if (ms->nvdimms_state->is_enabled) {
>          nvdimm_build_srat(table_data);
>      }
> diff --git a/include/hw/acpi/acpi-generic-initiator.h b/include/hw/acpi/acpi-generic-initiator.h
> index 2f183b029a..213545e614 100644
> --- a/include/hw/acpi/acpi-generic-initiator.h
> +++ b/include/hw/acpi/acpi-generic-initiator.h
> @@ -29,4 +29,30 @@ typedef struct AcpiGenericInitiatorClass {
>          ObjectClass parent_class;
>  } AcpiGenericInitiatorClass;
>  
> +/*
> + * ACPI 6.3:
> + * Table 5-81 Flags – Generic Initiator Affinity Structure
> + */
> +typedef enum {
> +    GEN_AFFINITY_ENABLED = (1 << 0), /*
> +                                      * If clear, the OSPM ignores the contents
> +                                      * of the Generic Initiator/Port Affinity
> +                                      * Structure. This allows system firmware
> +                                      * to populate the SRAT with a static
> +                                      * number of structures, but only enable
> +                                      * them as necessary.
> +                                      */
I'd put the comment above the definition to avoid wrapping so much!
> +} GenericAffinityFlags;
> +
> +/*
> + * ACPI 6.3:
> + * Table 5-80 Device Handle - PCI
> + */
> +typedef struct PCIDeviceHandle {
> +    uint16_t segment;
> +    uint16_t bdf;
> +} PCIDeviceHandle;
> +
> +void build_srat_generic_pci_initiator(GArray *table_data);
> +
>  #endif