Re: [PATCH v7 17/23] iommufd: Introduce a helper function to extract vendor capabilities

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

On 10/24/25 10:43 AM, Zhenzhong Duan wrote:
> In VFIO core, we call iommufd_backend_get_device_info() to return vendor
> specific hardware information data, but it's not good to extract this raw
> data in VFIO core.
>
> Introduce host_iommu_extract_quirks() to help extracting the raw data and
> return a bitmap in iommufd.c because it's the place defining
> iommufd_backend_get_device_info().
>
> The other choice is to put vendor data extracting code in vendor vIOMMU
> emulation file, but that will make those files mixed with vIOMMU
> emulation and host IOMMU extracting code, also need a new callback in
> PCIIOMMUOps. So we choose a simpler way as above.
up to now iommufd.c was arch independent. And on the other hand you
started to put iommufd specific info in intel_iommu.c so I am wondering
whether this is the good place to put this helper. Again, maybe consider
consider creating  an intel_iommu_accel.c or something alike

Eric
>
> Suggested-by: Nicolin Chen <nicolinc@nvidia.com>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>  include/hw/iommu.h                 |  5 +++++
>  include/system/host_iommu_device.h | 15 +++++++++++++++
>  backends/iommufd.c                 | 13 +++++++++++++
>  3 files changed, 33 insertions(+)
>
> diff --git a/include/hw/iommu.h b/include/hw/iommu.h
> index 9b8bb94fc2..6d61410703 100644
> --- a/include/hw/iommu.h
> +++ b/include/hw/iommu.h
> @@ -22,4 +22,9 @@ enum viommu_flags {
>      VIOMMU_FLAG_WANT_NESTING_PARENT = BIT_ULL(0),
>  };
>  
> +/* Host IOMMU quirks. Extracted from host IOMMU capabilities */
> +enum host_iommu_quirks {
> +    HOST_IOMMU_QUIRK_NESTING_PARENT_BYPASS_RO = BIT_ULL(0),
> +};
> +
>  #endif /* HW_IOMMU_H */
> diff --git a/include/system/host_iommu_device.h b/include/system/host_iommu_device.h
> index ab849a4a82..9ae7f4cc6d 100644
> --- a/include/system/host_iommu_device.h
> +++ b/include/system/host_iommu_device.h
> @@ -39,6 +39,21 @@ typedef struct HostIOMMUDeviceCaps {
>      uint64_t hw_caps;
>      VendorCaps vendor_caps;
>  } HostIOMMUDeviceCaps;
> +
> +/**
> + * host_iommu_extract_quirk: Extract host IOMMU quirks
> + *
> + * This function converts @type specific hardware information data
> + * into a standard bitmap format.
> + *
> + * @type: IOMMU Hardware Info Types
> + *
> + * @VendorCaps: IOMMU @type specific hardware information data
> + *
> + * Returns: bitmap with each representing a host IOMMU quirk defined in
s/each/each bit
> + * enum host_iommu_quirks
> + */
> +uint64_t host_iommu_extract_quirks(uint32_t type, VendorCaps *caps);
>  #endif
>  
>  #define TYPE_HOST_IOMMU_DEVICE "host-iommu-device"
> diff --git a/backends/iommufd.c b/backends/iommufd.c
> index 086bd67aea..61b991ec53 100644
> --- a/backends/iommufd.c
> +++ b/backends/iommufd.c
> @@ -19,6 +19,7 @@
>  #include "migration/cpr.h"
>  #include "monitor/monitor.h"
>  #include "trace.h"
> +#include "hw/iommu.h"
>  #include "hw/vfio/vfio-device.h"
>  #include <sys/ioctl.h>
>  #include <linux/iommufd.h>
> @@ -411,6 +412,18 @@ bool iommufd_backend_get_device_info(IOMMUFDBackend *be, uint32_t devid,
>      return true;
>  }
>  
> +uint64_t host_iommu_extract_quirks(uint32_t type, VendorCaps *caps)
> +{
> +    uint64_t quirks = 0;
> +
> +    if (type == IOMMU_HW_INFO_TYPE_INTEL_VTD &&
> +        caps->vtd.flags & IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17) {
> +        quirks |= HOST_IOMMU_QUIRK_NESTING_PARENT_BYPASS_RO;
> +    }
> +
> +    return quirks;
> +}
> +
>  bool iommufd_backend_invalidate_cache(IOMMUFDBackend *be, uint32_t id,
>                                        uint32_t data_type, uint32_t entry_len,
>                                        uint32_t *entry_num, void *data,