Hi Shameer,
On 9/29/25 3:36 PM, Shameer Kolothum wrote:
> For accelerated SMMUv3, we need nested parent domain creation. Add the
> callback support so that VFIO can create a nested parent.
>
> In the accelerated SMMUv3 case, the host SMMUv3 is configured in nested
> mode (S1 + S2), and the guest owns the Stage-1 page table. Therefore, we
> expose only Stage-1 to the guest to ensure it uses the correct page-table
> format.
>
> Reviewed-by: Nicolin Chen <[email protected]>
> Signed-off-by: Shameer Kolothum <[email protected]>
> Signed-off-by: Shameer Kolothum <[email protected]>
Wonder if you shall keep both. I don't know the usage though but worth
to check.
> ---
> hw/arm/smmuv3-accel.c | 13 +++++++++++++
> hw/arm/virt.c | 13 +++++++++++++
> 2 files changed, 26 insertions(+)
>
> diff --git a/hw/arm/smmuv3-accel.c b/hw/arm/smmuv3-accel.c
> index 44410cfb2a..6b0e512d86 100644
> --- a/hw/arm/smmuv3-accel.c
> +++ b/hw/arm/smmuv3-accel.c
> @@ -10,6 +10,7 @@
> #include "qemu/error-report.h"
>
> #include "hw/arm/smmuv3.h"
> +#include "hw/iommu.h"
> #include "hw/pci/pci_bridge.h"
> #include "hw/pci-host/gpex.h"
> #include "hw/vfio/pci.h"
> @@ -106,8 +107,20 @@ static AddressSpace *smmuv3_accel_find_add_as(PCIBus
> *bus, void *opaque,
> }
> }
>
> +static uint64_t smmuv3_accel_get_viommu_flags(void *opaque)
> +{
> + /*
> + * We return VIOMMU_FLAG_WANT_NESTING_PARENT to inform VFIO core to
> create a
> + * nesting parent which is required for accelerated SMMUv3 support.
> + * The real HW nested support should be reported from host SMMUv3 and if
> + * it doesn't, the nesting parent allocation will fail anyway in VFIO
> core.
> + */
> + return VIOMMU_FLAG_WANT_NESTING_PARENT;
> +}
> +
> static const PCIIOMMUOps smmuv3_accel_ops = {
> .get_address_space = smmuv3_accel_find_add_as,
> + .get_viommu_flags = smmuv3_accel_get_viommu_flags,
> };
>
> void smmuv3_accel_init(SMMUv3State *s)
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 02209fadcf..b533b0556e 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -3073,6 +3073,19 @@ static void virt_machine_device_plug_cb(HotplugHandler
> *hotplug_dev,
> return;
> }
>
> + if (object_property_get_bool(OBJECT(dev), "accel",
> &error_abort)) {
This looks unrelated to the get_viommu_flags() addition and to me this
shall be put in a separate patch of squashed in the patch that exposes
the accel prop Thanks Eric
> + char *stage;
> +
> + stage = object_property_get_str(OBJECT(dev), "stage",
> + &error_fatal);
> + /* If no stage specified, SMMUv3 will default to stage 1 */
> + if (*stage && strcmp("1", stage)) {
> + error_setg(errp, "Only stage1 is supported for SMMUV3
> with "
> + "accel=on");
> + return;
> + }
> + }
> +
> create_smmuv3_dev_dtb(vms, dev, bus);
> }
> }
