>-----Original Message-----
>From: Cédric Le Goater <c...@redhat.com>
>Subject: Re: [PATCH v1 6/6] iommufd: Implement query of host VTD IOMMU's
>capability
>
>On 5/28/25 08:04, Zhenzhong Duan wrote:
>> Implement query of HOST_IOMMU_DEVICE_CAP_[NESTING|FS1GP|ERRATA]
>for IOMMUFD
>> backed host VTD IOMMU device.
>>
>> Query on these capabilities is not supported for legacy backend because there
>> is no plan to support nesting with legacy backend backed host device.
>>
>> Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
>> ---
>> hw/i386/intel_iommu_internal.h | 1 +
>> include/system/host_iommu_device.h | 7 ++++++
>> backends/iommufd.c | 39 ++++++++++++++++++++++++++++--
>> 3 files changed, 45 insertions(+), 2 deletions(-)
>>
>> 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/include/system/host_iommu_device.h
>b/include/system/host_iommu_device.h
>> index 10fccc10be..c2770cb469 100644
>> --- a/include/system/host_iommu_device.h
>> +++ b/include/system/host_iommu_device.h
>> @@ -29,6 +29,10 @@ typedef union VendorCaps {
>> *
>> * @hw_caps: host platform IOMMU capabilities (e.g. on IOMMUFD this
>represents
>> * the @out_capabilities value returned from IOMMU_GET_HW_INFO
>ioctl)
>> + *
>> + * @vendor_caps: host platform IOMMU vendor specific capabilities (e.g. on
>> + * IOMMUFD this represents raw vendor data from data_uptr
>> + * buffer returned from IOMMU_GET_HW_INFO ioctl)
>> */
>> typedef struct HostIOMMUDeviceCaps {
>> uint32_t type;
>> @@ -116,6 +120,9 @@ struct HostIOMMUDeviceClass {
>> */
>> #define HOST_IOMMU_DEVICE_CAP_IOMMU_TYPE 0
>> #define HOST_IOMMU_DEVICE_CAP_AW_BITS 1
>> +#define HOST_IOMMU_DEVICE_CAP_NESTING 2
>> +#define HOST_IOMMU_DEVICE_CAP_FS1GP 3
>> +#define HOST_IOMMU_DEVICE_CAP_ERRATA 4
>>
>> #define HOST_IOMMU_DEVICE_CAP_AW_BITS_MAX 64
>> #endif
>> diff --git a/backends/iommufd.c b/backends/iommufd.c
>> index b114fb08e7..63209659f3 100644
>> --- a/backends/iommufd.c
>> +++ b/backends/iommufd.c
>> @@ -21,6 +21,7 @@
>> #include "hw/vfio/vfio-device.h"
>> #include <sys/ioctl.h>
>> #include <linux/iommufd.h>
>> +#include "hw/i386/intel_iommu_internal.h"
>>
>> static void iommufd_backend_init(Object *obj)
>> {
>> @@ -364,6 +365,41 @@ bool
>host_iommu_device_iommufd_detach_hwpt(HostIOMMUDeviceIOMMUFD *idev,
>> return idevc->detach_hwpt(idev, errp);
>> }
>>
>> +static int hiod_iommufd_get_vtd_cap(HostIOMMUDevice *hiod, int cap,
>> + Error **errp)
>> +{
>> + struct iommu_hw_info_vtd *caps = &hiod->caps.vendor_caps.vtd;
>> +
>> + switch (cap) {
>> + case HOST_IOMMU_DEVICE_CAP_NESTING:
>> + return !!(caps->ecap_reg & VTD_ECAP_NEST);
>> + case HOST_IOMMU_DEVICE_CAP_FS1GP:
>> + return !!(caps->cap_reg & VTD_CAP_FS1GP);
>> + case HOST_IOMMU_DEVICE_CAP_ERRATA:
>> + return caps->flags & IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17;
>> + default:
>> + error_setg(errp, "%s: unsupported capability %x", hiod->name, cap);
>> + return -EINVAL;
>> + }
>> +}
>
>
>This is intel specific. Why not handle these capabilities directly from
>vtd_check_hiod() under hw/i386/intel_iommu.c ?
Do you mean checking hiod->caps.vendor_caps.vtd.ecap/cap_reg directly
in intel_iommu.c and drop vendor cap checking by .get_cap()? That's fine
if we don't have plan to support virtio-iommu querying vendor caps in a
standard way.
Thanks
Zhenzhong
