Re: [PATCH v3 6/6] hw/arm/virt: Allow user-creatable SMMUv3 dev instantiation

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

On 6/2/25 5:41 PM, Shameer Kolothum 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.
>
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> ---
>  hw/arm/smmuv3.c      |  2 ++
>  hw/arm/virt.c        | 50 ++++++++++++++++++++++++++++++++++++++++++++
>  hw/core/sysbus-fdt.c |  3 +++
>  3 files changed, 55 insertions(+)
>
> diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
> index 7e934336c2..d1f66dcd8f 100644
> --- a/hw/arm/smmuv3.c
> +++ b/hw/arm/smmuv3.c
> @@ -2004,6 +2004,8 @@ 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..04bc940fc3 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);
> +}
wondering whether you couldn't have put that code in hw/core/sysbus-fdt.c
just like add_calxeda_midway_xgmac_fdt_node(). vms can be retrieved from
the object hierarchy I guess.

Actually the original infra was made in that spirit. Now I know that
Peter is not a big fan of all those VFIO platform related stuff ;-) so I
have no strong opinion either.
> +
>  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 +2984,25 @@ 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);
> +            if (vms->iommu != VIRT_IOMMU_SMMUV3) {
is it worth to check given the check done in
virt_machine_device_pre_plug_cb()?
        if (vms->legacy_smmuv3_present || vms->iommu == VIRT_IOMMU_VIRTIO) {

Cheers

Eric
> +                vms->iommu = VIRT_IOMMU_SMMUV3;
> +            }
> +        }
> +    }
> +
>      if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI)) {
>          PCIDevice *pdev = PCI_DEVICE(dev);
>  
> @@ -3156,6 +3205,7 @@ static void virt_machine_class_init(ObjectClass *oc, const void *data)
>      machine_class_allow_dynamic_sysbus_dev(mc, TYPE_RAMFB_DEVICE);
>      machine_class_allow_dynamic_sysbus_dev(mc, TYPE_VFIO_PLATFORM);
>      machine_class_allow_dynamic_sysbus_dev(mc, TYPE_UEFI_VARS_SYSBUS);
> +    machine_class_allow_dynamic_sysbus_dev(mc, TYPE_ARM_SMMUV3);
>  #ifdef CONFIG_TPM
>      machine_class_allow_dynamic_sysbus_dev(mc, TYPE_TPM_TIS_SYSBUS);
>  #endif
> diff --git a/hw/core/sysbus-fdt.c b/hw/core/sysbus-fdt.c
> index c339a27875..e80776080b 100644
> --- a/hw/core/sysbus-fdt.c
> +++ b/hw/core/sysbus-fdt.c
> @@ -31,6 +31,7 @@
>  #include "qemu/error-report.h"
>  #include "system/device_tree.h"
>  #include "system/tpm.h"
> +#include "hw/arm/smmuv3.h"
>  #include "hw/platform-bus.h"
>  #include "hw/vfio/vfio-platform.h"
>  #include "hw/vfio/vfio-calxeda-xgmac.h"
> @@ -518,6 +519,8 @@ static const BindingEntry bindings[] = {
>  #ifdef CONFIG_TPM
>      TYPE_BINDING(TYPE_TPM_TIS_SYSBUS, add_tpm_tis_fdt_node),
>  #endif
> +    /* No generic DT support for smmuv3 dev. Support added for arm virt only */
> +    TYPE_BINDING(TYPE_ARM_SMMUV3, no_fdt_node),
>      TYPE_BINDING(TYPE_RAMFB_DEVICE, no_fdt_node),
>      TYPE_BINDING(TYPE_UEFI_VARS_SYSBUS, add_uefi_vars_node),
>      TYPE_BINDING("", NULL), /* last element */