Re: [PATCH v4 6/7] hw/arm/virt: Allow user-creatable SMMUv3 dev instantiation

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

On Fri, 13 Jun 2025 15:44:48 +0100
Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> wrote:

> Allow cold-plug of smmuv3 device to virt if there is no machine
> wide legacy smmuv3 or a virtio-iommu is specified.
> 
> Device tree support for new smmuv3 dev is limited to the case where
> it is associated with the default pcie.0 RC.
> 
> Tested-by: Nathan Chen <nathanc@nvidia.com>
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>

Looks good to me. 
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

> ---
>  hw/arm/smmuv3.c      |  2 ++
>  hw/arm/virt.c        | 47 ++++++++++++++++++++++++++++++++++++++++++++
>  hw/core/sysbus-fdt.c |  3 +++
>  3 files changed, 52 insertions(+)
> 
> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> index ab67972353..bcf8af8dc7 100644
> --- a/hw/arm/smmuv3.c
> +++ b/hw/arm/smmuv3.c
> @@ -1996,6 +1996,8 @@ static void smmuv3_class_init(ObjectClass *klass, const void *data)
>      device_class_set_parent_realize(dc, smmu_realize,
>                                      &c->parent_realize);
>      device_class_set_props(dc, smmuv3_properties);
> +    dc->hotpluggable = false;
> +    dc->user_creatable = true;
>  }
>  
>  static int smmuv3_notify_flag_changed(IOMMUMemoryRegion *iommu,
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index eeace4754d..3be007d87c 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -56,6 +56,7 @@
>  #include "qemu/cutils.h"
>  #include "qemu/error-report.h"
>  #include "qemu/module.h"
> +#include "hw/pci/pci_bus.h"
>  #include "hw/pci-host/gpex.h"
>  #include "hw/virtio/virtio-pci.h"
>  #include "hw/core/sysbus-fdt.h"
> @@ -1443,6 +1444,28 @@ static void create_smmuv3_dt_bindings(const VirtMachineState *vms, hwaddr base,
>      g_free(node);
>  }
>  
> +static void create_smmuv3_dev_dtb(VirtMachineState *vms,
> +                                  DeviceState *dev, PCIBus *bus)
> +{
> +    PlatformBusDevice *pbus = PLATFORM_BUS_DEVICE(vms->platform_bus_dev);
> +    SysBusDevice *sbdev = SYS_BUS_DEVICE(dev);
> +    int irq = platform_bus_get_irqn(pbus, sbdev, 0);
> +    hwaddr base = platform_bus_get_mmio_addr(pbus, sbdev, 0);
> +    MachineState *ms = MACHINE(vms);
> +
> +    if (strcmp("pcie.0", bus->qbus.name)) {
> +        warn_report("SMMUv3 device only supported with pcie.0 for DT");
> +        return;
> +    }
> +    base += vms->memmap[VIRT_PLATFORM_BUS].base;
> +    irq += vms->irqmap[VIRT_PLATFORM_BUS];
> +
> +    vms->iommu_phandle = qemu_fdt_alloc_phandle(ms->fdt);
> +    create_smmuv3_dt_bindings(vms, base, SMMU_IO_LEN, irq);
> +    qemu_fdt_setprop_cells(ms->fdt, vms->pciehb_nodename, "iommu-map",
> +                           0x0, vms->iommu_phandle, 0x0, 0x10000);
> +}
> +
>  static void create_smmu(const VirtMachineState *vms,
>                          PCIBus *bus)
>  {
> @@ -2931,6 +2954,13 @@ static void virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
>          qlist_append_str(reserved_regions, resv_prop_str);
>          qdev_prop_set_array(dev, "reserved-regions", reserved_regions);
>          g_free(resv_prop_str);
> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_ARM_SMMUV3)) {
> +        if (vms->legacy_smmuv3_present || vms->iommu == VIRT_IOMMU_VIRTIO) {
> +            error_setg(errp, "virt machine already has %s set. "
> +                       "Doesn't support incompatible iommus",
> +                       (vms->legacy_smmuv3_present) ?
> +                       "iommu=smmuv3" : "virtio-iommu");
> +        }
>      }
>  }
>  
> @@ -2954,6 +2984,22 @@ static void virt_machine_device_plug_cb(HotplugHandler *hotplug_dev,
>          virtio_md_pci_plug(VIRTIO_MD_PCI(dev), MACHINE(hotplug_dev), errp);
>      }
>  
> +    if (object_dynamic_cast(OBJECT(dev), TYPE_ARM_SMMUV3)) {
> +        if (!vms->legacy_smmuv3_present && vms->platform_bus_dev) {
> +            PCIBus *bus;
> +
> +            bus = PCI_BUS(object_property_get_link(OBJECT(dev), "primary-bus",
> +                                                   &error_abort));
> +            if (pci_bus_bypass_iommu(bus)) {
> +                error_setg(errp, "Bypass option cannot be set for SMMUv3 "
> +                           "associated PCIe RC");
> +                return;
> +            }
> +
> +            create_smmuv3_dev_dtb(vms, dev, bus);
> +        }
> +    }
> +