Re: [PATCH rfcv2 07/20] iommufd: Implement query of HOST_IOMMU_DEVICE_CAP_[NESTING|FS1GP]

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

On 2/19/25 9:22 AM, Zhenzhong Duan wrote:
> Implement query of HOST_IOMMU_DEVICE_CAP_[NESTING|FS1GP] for IOMMUFD
> backed host IOMMU device.
>
> Query on these two capabilities is not supported for legacy backend
> because there is no plan to support nesting with leacy backend backed
> host device.
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
> ---
>  hw/i386/intel_iommu_internal.h |  1 +
>  backends/iommufd.c             |  4 ++++
>  hw/vfio/iommufd.c              | 11 +++++++++++
>  3 files changed, 16 insertions(+)
>
> diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> index e8b211e8b0..2cda744786 100644
> --- a/hw/i386/intel_iommu_internal.h
> +++ b/hw/i386/intel_iommu_internal.h
> @@ -191,6 +191,7 @@
>  #define VTD_ECAP_PT                 (1ULL << 6)
>  #define VTD_ECAP_SC                 (1ULL << 7)
>  #define VTD_ECAP_MHMV               (15ULL << 20)
> +#define VTD_ECAP_NEST               (1ULL << 26)
>  #define VTD_ECAP_SRS                (1ULL << 31)
>  #define VTD_ECAP_PASID              (1ULL << 40)
>  #define VTD_ECAP_SMTS               (1ULL << 43)
> diff --git a/backends/iommufd.c b/backends/iommufd.c
> index 574f330c27..0a1a40cbba 100644
> --- a/backends/iommufd.c
> +++ b/backends/iommufd.c
> @@ -370,6 +370,10 @@ static int hiod_iommufd_get_cap(HostIOMMUDevice *hiod, int cap, Error **errp)
>          return caps->type;
>      case HOST_IOMMU_DEVICE_CAP_AW_BITS:
>          return vfio_device_get_aw_bits(hiod->agent);
> +    case HOST_IOMMU_DEVICE_CAP_NESTING:
> +        return caps->nesting;
> +    case HOST_IOMMU_DEVICE_CAP_FS1GP:
> +        return caps->fs1gp;
this is vtd specific so those caps shouldn't be return for other iommus, no?

Eric
>      default:
>          error_setg(errp, "%s: unsupported capability %x", hiod->name, cap);
>          return -EINVAL;
> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
> index 175c4fe1f4..df6a12d200 100644
> --- a/hw/vfio/iommufd.c
> +++ b/hw/vfio/iommufd.c
> @@ -26,6 +26,7 @@
>  #include "qemu/chardev_open.h"
>  #include "pci.h"
>  #include "exec/ram_addr.h"
> +#include "hw/i386/intel_iommu_internal.h"
>  
>  static int iommufd_cdev_map(const VFIOContainerBase *bcontainer, hwaddr iova,
>                              ram_addr_t size, void *vaddr, bool readonly)
> @@ -843,6 +844,16 @@ static bool hiod_iommufd_vfio_realize(HostIOMMUDevice *hiod, void *opaque,
>      caps->type = type;
>      caps->hw_caps = hw_caps;
>  
> +    switch (type) {
> +    case IOMMU_HW_INFO_TYPE_INTEL_VTD:
> +        caps->nesting = !!(data.vtd.ecap_reg & VTD_ECAP_NEST);
> +        caps->fs1gp = !!(data.vtd.cap_reg & VTD_CAP_FS1GP);
> +        break;
> +    case IOMMU_HW_INFO_TYPE_ARM_SMMUV3:
> +    case IOMMU_HW_INFO_TYPE_NONE:
> +        break;
> +    }
> +
>      return true;
>  }
>