Re: [PATCH v5 01/11] hw/arm/smmu-common: Check SMMU has PCIe Root Complex association

[Eric Auger <eric.auger@redhat.com>]

Hi Shameer,

On 6/23/25 11:42 AM, Shameer Kolothum wrote:
> We only allow default PCIe Root Complex(pcie.0) or pxb-pcie based extra
> root complexes to be associated with SMMU.
>
> Although this change does not affect functionality at present, it is
> required when we add support for user-creatable SMMUv3 devices in
> future patches.
>
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> ---
>  hw/arm/smmu-common.c                | 29 ++++++++++++++++++++++++++---
>  hw/pci-bridge/pci_expander_bridge.c |  1 -
>  include/hw/pci/pci_bridge.h         |  1 +
>  3 files changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/hw/arm/smmu-common.c b/hw/arm/smmu-common.c
> index f39b99e526..b15e7fd0e4 100644
> --- a/hw/arm/smmu-common.c
> +++ b/hw/arm/smmu-common.c
> @@ -20,6 +20,7 @@
>  #include "trace.h"
>  #include "exec/target_page.h"
>  #include "hw/core/cpu.h"
> +#include "hw/pci/pci_bridge.h"
>  #include "hw/qdev-properties.h"
>  #include "qapi/error.h"
>  #include "qemu/jhash.h"
> @@ -925,6 +926,7 @@ static void smmu_base_realize(DeviceState *dev, Error **errp)
>  {
>      SMMUState *s = ARM_SMMU(dev);
>      SMMUBaseClass *sbc = ARM_SMMU_GET_CLASS(dev);
> +    PCIBus *pci_bus = s->primary_bus;
>      Error *local_err = NULL;
>  
>      sbc->parent_realize(dev, &local_err);
> @@ -937,11 +939,32 @@ static void smmu_base_realize(DeviceState *dev, Error **errp)
>                                       g_free, g_free);
>      s->smmu_pcibus_by_busptr = g_hash_table_new(NULL, NULL);
>  
> -    if (s->primary_bus) {
> -        pci_setup_iommu(s->primary_bus, &smmu_ops, s);
> -    } else {
> +    if (!pci_bus) {
>          error_setg(errp, "SMMU is not attached to any PCI bus!");
> +        return;
> +    }
> +
> +    /*
> +     * We only allow default PCIe Root Complex(pcie.0) or pxb-pcie based extra
> +     * root complexes to be associated with SMMU.
> +     */
> +    if (pci_bus_is_express(pci_bus) && pci_bus_is_root(pci_bus) &&
> +        object_dynamic_cast(OBJECT(pci_bus)->parent, TYPE_PCI_HOST_BRIDGE)) {
> +        /*
> +         * For pxb-pcie, parent_dev will be set. Make sure it is
> +         * pxb-pcie indeed.
> +         */
> +        if (pci_bus->parent_dev) {
> +            if (!object_dynamic_cast(OBJECT(pci_bus), TYPE_PXB_PCIE_BUS)) {
> +                goto out_err;
> +            }
I still wonder whether the above check was mandated as it works for what
it is meant:

Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> +        }
> +        pci_setup_iommu(pci_bus, &smmu_ops, s);
> +        return;
>      }
> +out_err:
> +    error_setg(errp, "SMMU should be attached to a default PCIe root complex"
> +               "(pcie.0) or a pxb-pcie based root complex");
>  }
>  
>  /*
> diff --git a/hw/pci-bridge/pci_expander_bridge.c b/hw/pci-bridge/pci_expander_bridge.c
> index 3a29dfefc2..1bcceddbc4 100644
> --- a/hw/pci-bridge/pci_expander_bridge.c
> +++ b/hw/pci-bridge/pci_expander_bridge.c
> @@ -34,7 +34,6 @@ typedef struct PXBBus PXBBus;
>  DECLARE_INSTANCE_CHECKER(PXBBus, PXB_BUS,
>                           TYPE_PXB_BUS)
>  
> -#define TYPE_PXB_PCIE_BUS "pxb-pcie-bus"
>  DECLARE_INSTANCE_CHECKER(PXBBus, PXB_PCIE_BUS,
>                           TYPE_PXB_PCIE_BUS)
>  
> diff --git a/include/hw/pci/pci_bridge.h b/include/hw/pci/pci_bridge.h
> index b0f5204d80..de0eba55b7 100644
> --- a/include/hw/pci/pci_bridge.h
> +++ b/include/hw/pci/pci_bridge.h
> @@ -104,6 +104,7 @@ typedef struct PXBPCIEDev {
>      PXBDev parent_obj;
>  } PXBPCIEDev;
>  
> +#define TYPE_PXB_PCIE_BUS "pxb-pcie-bus"
>  #define TYPE_PXB_CXL_BUS "pxb-cxl-bus"
>  #define TYPE_PXB_DEV "pxb"
>  OBJECT_DECLARE_SIMPLE_TYPE(PXBDev, PXB_DEV)