On 10/28/25 7:57 AM, Duan, Zhenzhong wrote:
>
>> -----Original Message-----
>> From: Cédric Le Goater <[email protected]>
>> Subject: Re: [PATCH v7 05/23] hw/pci: Introduce
>> pci_device_get_viommu_flags()
>>
>> On 10/24/25 10:43, Zhenzhong Duan wrote:
>>> Introduce a new PCIIOMMUOps optional callback, get_viommu_flags()
>> which
>>> allows to retrieve flags exposed by a vIOMMU. The first planned vIOMMU
>>> device flag is VIOMMU_FLAG_WANT_NESTING_PARENT that advertises the
>>> support of HW nested stage translation scheme and wants other sub-system
>>> like VFIO's cooperation to create nesting parent HWPT.
>>>
>>> pci_device_get_viommu_flags() is a wrapper that can be called on a PCI
>>> device potentially protected by a vIOMMU.
>>>
>>> get_viommu_flags() is designed to return 64bit bitmap of purely vIOMMU
>>> flags which are only determined by user's configuration, no host
>>> capabilities involved. Reasons are:
>>>
>>> 1. host may has heterogeneous IOMMUs, each with different capabilities
>>> 2. this is migration friendly, return value is consistent between source
>>> and target.
>>>
>>> Note that this op will be invoked at the attach_device() stage, at which
>>> point host IOMMU capabilities are not yet forwarded to the vIOMMU
>> through
>>> the set_iommu_device() callback that will be after the attach_device().
>>>
>>> See below sequence:
>>>
>>> vfio_device_attach():
>>> iommufd_cdev_attach():
>>> pci_device_get_viommu_flags() for HW nesting cap
>>> create a nesting parent HWPT
>>> attach device to the HWPT
>>> vfio_device_hiod_create_and_realize() creating hiod
>>> ...
>>> pci_device_set_iommu_device(hiod)
>>>
>>> Suggested-by: Yi Liu <[email protected]>
>>> Signed-off-by: Zhenzhong Duan <[email protected]>
>>> Reviewed-by: Nicolin Chen <[email protected]>
>>> Reviewed-by: Eric Auger <[email protected]>
>>> Reviewed-by: Yi Liu <[email protected]>
>>> ---
>>> MAINTAINERS | 1 +
>>> include/hw/iommu.h | 25 +++++++++++++++++++++++++
>>
>> Hmm, why not under include/hw/pci/ ?
> I'm not sure if it's better to restrict iommu to pci subsystem.
> I have a vague memory there is iommu supporting non-PCI devices.
effectively on ARM we may need to support SMMU for platform devices too
Eric
>
>> Was this discussed ?
> No.
>
> Thanks
> Zhenzhong
>
>>
>> Reviewed-by: Cédric Le Goater <[email protected]>
>>
>> Thanks,
>>
>> C.
>>
>>
>>
>>> include/hw/pci/pci.h | 22 ++++++++++++++++++++++
>>> hw/pci/pci.c | 11 +++++++++++
>>> 4 files changed, 59 insertions(+)
>>> create mode 100644 include/hw/iommu.h
>>>
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index 36eef27b41..d94fbcbdfb 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -2338,6 +2338,7 @@ 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..9b8bb94fc2
>>> --- /dev/null
>>> +++ b/include/hw/iommu.h
>>> @@ -0,0 +1,25 @@
>>> +/*
>>> + * General vIOMMU flags
>>> + *
>>> + * Copyright (C) 2025 Intel Corporation.
>>> + *
>>> + * SPDX-License-Identifier: GPL-2.0-or-later
>>> + */
>>> +
>>> +#ifndef HW_IOMMU_H
>>> +#define HW_IOMMU_H
>>> +
>>> +#include "qemu/bitops.h"
>>> +
>>> +/*
>>> + * Theoretical vIOMMU flags. Only determined by the vIOMMU device
>> properties and
>>> + * independent on the actual host IOMMU capabilities they may depend on.
>> Each
>>> + * flag can be an expectation or request to other sub-system or just a pure
>>> + * vIOMMU capability. vIOMMU can choose which flags to expose.
>>> + */
>>> +enum viommu_flags {
>>> + /* vIOMMU needs nesting parent HWPT to create nested HWPT */
>>> + VIOMMU_FLAG_WANT_NESTING_PARENT = BIT_ULL(0),
>>> +};
>>> +
>>> +#endif /* HW_IOMMU_H */
>>> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
>>> index bde9dca8e2..cf99b5bb68 100644
>>> --- a/include/hw/pci/pci.h
>>> +++ b/include/hw/pci/pci.h
>>> @@ -462,6 +462,18 @@ typedef struct PCIIOMMUOps {
>>> * @devfn: device and function number of the PCI device.
>>> */
>>> void (*unset_iommu_device)(PCIBus *bus, void *opaque, int devfn);
>>> + /**
>>> + * @get_viommu_flags: get vIOMMU flags
>>> + *
>>> + * Optional callback, if not implemented, then vIOMMU doesn't
>> support
>>> + * exposing flags to other sub-system, e.g., VFIO.
>>> + *
>>> + * @opaque: the data passed to pci_setup_iommu().
>>> + *
>>> + * Returns: bitmap with each representing a vIOMMU flag defined in
>>> + * enum viommu_flags.
>>> + */
>>> + uint64_t (*get_viommu_flags)(void *opaque);
>>> /**
>>> * @get_iotlb_info: get properties required to initialize a device
>> IOTLB.
>>> *
>>> @@ -644,6 +656,16 @@ bool pci_device_set_iommu_device(PCIDevice
>> *dev, HostIOMMUDevice *hiod,
>>> Error **errp);
>>> void pci_device_unset_iommu_device(PCIDevice *dev);
>>>
>>> +/**
>>> + * pci_device_get_viommu_flags: get vIOMMU flags.
>>> + *
>>> + * Returns: bitmap with each representing a vIOMMU flag defined in
>>> + * enum viommu_flags. Or 0 if vIOMMU doesn't report any.
>>> + *
>>> + * @dev: PCI device pointer.
>>> + */
>>> +uint64_t pci_device_get_viommu_flags(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 d0e81651aa..c9932c87e3 100644
>>> --- a/hw/pci/pci.c
>>> +++ b/hw/pci/pci.c
>>> @@ -3010,6 +3010,17 @@ void
>> pci_device_unset_iommu_device(PCIDevice *dev)
>>> }
>>> }
>>>
>>> +uint64_t pci_device_get_viommu_flags(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_flags) {
>>> + return
>> iommu_bus->iommu_ops->get_viommu_flags(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)
