Hi Zhenzhong,
On Tue, Jul 29, 2025 at 5:21 PM Zhenzhong Duan <[email protected]> wrote:
>
> Introduce a new PCIIOMMUOps optional callback, get_viommu_cap() which
> allows to retrieve capabilities exposed by a vIOMMU. The first planned
> capability is VIOMMU_CAP_HW_NESTED that advertises the support of HW
> nested stage translation scheme. pci_device_get_viommu_cap is a wrapper
> that can be called on a PCI device potentially protected by a vIOMMU.
>
> get_viommu_cap() is designed to return 64bit bitmap of purely emulated
> capabilities which are only derermined by user's configuration, no host
> capabilities involved. Reasons are:
>
> 1. there can be more than one host IOMMUs with different capabilities
> 2. there can also be more than one vIOMMUs with different user
> configuration, e.g., arm smmuv3.
> 3. This is migration friendly, return value is consistent between source
> and target.
> 4. It's too late for VFIO to call get_viommu_cap() after set_iommu_device()
> because we need get_viommu_cap() to determine if creating nested parent
> hwpt or not at attaching stage, meanwhile hiod realize needs iommufd,
> devid and hwpt_id which are ready after attach_device().
> See below sequence:
>
> attach_device()
> get_viommu_cap()
> create hwpt
> ...
> create hiod
> set_iommu_device(hiod)
>
> Suggested-by: Yi Liu <[email protected]>
> Signed-off-by: Zhenzhong Duan <[email protected]>
> ---
> MAINTAINERS | 1 +
> include/hw/iommu.h | 17 +++++++++++++++++
> include/hw/pci/pci.h | 25 +++++++++++++++++++++++++
> hw/pci/pci.c | 11 +++++++++++
> 4 files changed, 54 insertions(+)
> create mode 100644 include/hw/iommu.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 37879ab64e..840cb1e604 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -2304,6 +2304,7 @@ F: include/system/iommufd.h
> F: backends/host_iommu_device.c
> F: include/system/host_iommu_device.h
> F: include/qemu/chardev_open.h
> +F: include/hw/iommu.h
> F: util/chardev_open.c
> F: docs/devel/vfio-iommufd.rst
>
> diff --git a/include/hw/iommu.h b/include/hw/iommu.h
> new file mode 100644
> index 0000000000..021db50db5
> --- /dev/null
> +++ b/include/hw/iommu.h
> @@ -0,0 +1,17 @@
> +/*
> + * General vIOMMU capabilities, flags, etc
> + *
> + * Copyright (C) 2025 Intel Corporation.
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef HW_IOMMU_H
> +#define HW_IOMMU_H
> +
Could we include header "qemu/bitops.h" here to use `BIT_ULL()` in this file?
Or it will get compile error when including it in the other IOMMU.
> +enum {
> + /* hardware nested stage-1 page table support */
> + VIOMMU_CAP_HW_NESTED = BIT_ULL(0),
> +};
> +
> +#endif /* HW_IOMMU_H */
> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> index 6b7d3ac8a3..d89aefc030 100644
> --- a/include/hw/pci/pci.h
> +++ b/include/hw/pci/pci.h
> @@ -462,6 +462,21 @@ typedef struct PCIIOMMUOps {
> * @devfn: device and function number of the PCI device.
> */
> void (*unset_iommu_device)(PCIBus *bus, void *opaque, int devfn);
> + /**
> + * @get_viommu_cap: get vIOMMU capabilities
> + *
> + * Optional callback, if not implemented, then vIOMMU doesn't
> + * support exposing capabilities to other subsystem, e.g., VFIO.
> + * vIOMMU can choose which capabilities to expose.
> + *
> + * @opaque: the data passed to pci_setup_iommu().
> + *
> + * Returns: 64bit bitmap with each bit represents a capability emulated
> by
> + * VIOMMU_CAP_* in include/hw/iommu.h, these capabilities are theoretical
> + * which are only determined by user's configuration and independent on
> the
> + * actual host capabilities they may depend on.
> + */
> + uint64_t (*get_viommu_cap)(void *opaque);
> /**
> * @get_iotlb_info: get properties required to initialize a device IOTLB.
> *
> @@ -642,6 +657,16 @@ bool pci_device_set_iommu_device(PCIDevice *dev,
> HostIOMMUDevice *hiod,
> Error **errp);
> void pci_device_unset_iommu_device(PCIDevice *dev);
>
> +/**
> + * pci_device_get_viommu_cap: get vIOMMU capabilities.
> + *
> + * Returns a 64bit bitmap with each bit represents a vIOMMU exposed
> + * capability, 0 if vIOMMU doesn't support esposing capabilities.
> + *
> + * @dev: PCI device pointer.
> + */
> +uint64_t pci_device_get_viommu_cap(PCIDevice *dev);
> +
> /**
> * pci_iommu_get_iotlb_info: get properties required to initialize a
> * device IOTLB.
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index c70b5ceeba..df1fb615a8 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -2992,6 +2992,17 @@ void pci_device_unset_iommu_device(PCIDevice *dev)
> }
> }
>
> +uint64_t pci_device_get_viommu_cap(PCIDevice *dev)
> +{
> + PCIBus *iommu_bus;
> +
> + pci_device_get_iommu_bus_devfn(dev, &iommu_bus, NULL, NULL);
> + if (iommu_bus && iommu_bus->iommu_ops->get_viommu_cap) {
> + return iommu_bus->iommu_ops->get_viommu_cap(iommu_bus->iommu_opaque);
> + }
> + return 0;
> +}
> +
> int pci_pri_request_page(PCIDevice *dev, uint32_t pasid, bool priv_req,
> bool exec_req, hwaddr addr, bool lpig,
> uint16_t prgi, bool is_read, bool is_write)
> --
> 2.47.1
>
>
Thanks,
Jim
