>-----Original Message-----
>From: Cédric Le Goater <[email protected]>
>Subject: Re: [RFC PATCH 03/14] vfio/iommufd: Create nesting parent hwpt with
>IOMMU_HWPT_ALLOC_PASID flag
>
>On 2/5/26 04:11, Zhenzhong Duan wrote:
>> When both host device and vIOMMU have PASID enabled, then guest may
>> setup pasid attached translation.
>>
>> We need to create the nesting parent hwpt with IOMMU_HWPT_ALLOC_PASID
>> flag because according to uAPI, any domain attached to the non-PASID
>> part of the device must also be flagged, otherwise attaching a PASID
>> will blocked.
>>
>> Introduce a vfio_device_get_viommu_flags_pasid_supported() helper to
>> facilitate this implementation.
>>
>> Signed-off-by: Zhenzhong Duan <[email protected]>
>> ---
>> include/hw/vfio/vfio-device.h | 1 +
>> hw/vfio/device.c | 11 +++++++++++
>> hw/vfio/iommufd.c | 8 +++++++-
>> 3 files changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/hw/vfio/vfio-device.h b/include/hw/vfio/vfio-device.h
>> index 35a5ec6d92..983eb0ecce 100644
>> --- a/include/hw/vfio/vfio-device.h
>> +++ b/include/hw/vfio/vfio-device.h
>> @@ -268,6 +268,7 @@ void vfio_device_prepare(VFIODevice *vbasedev,
>VFIOContainer *bcontainer,
>> void vfio_device_unprepare(VFIODevice *vbasedev);
>>
>> bool vfio_device_get_viommu_flags_want_nesting(VFIODevice *vbasedev);
>> +bool vfio_device_get_viommu_flags_pasid_supported(VFIODevice *vbasedev);
>> bool vfio_device_get_host_iommu_quirk_bypass_ro(VFIODevice *vbasedev,
>> uint32_t type, void *caps,
>> uint32_t size);
>> diff --git a/hw/vfio/device.c b/hw/vfio/device.c
>> index 973fc35b59..b15ca6ef0a 100644
>> --- a/hw/vfio/device.c
>> +++ b/hw/vfio/device.c
>> @@ -533,6 +533,17 @@ bool
>vfio_device_get_viommu_flags_want_nesting(VFIODevice *vbasedev)
>> return false;
>> }
>>
>> +bool vfio_device_get_viommu_flags_pasid_supported(VFIODevice *vbasedev)
>> +{
>> + VFIOPCIDevice *vdev = vfio_pci_from_vfio_device(vbasedev);
>> +
>> + if (vdev) {
>> + return !!(pci_device_get_viommu_flags(PCI_DEVICE(vdev)) &
>> + VIOMMU_FLAG_PASID_SUPPORTED);
>> + }
>> + return false;
>> +}
>> +
>> bool vfio_device_get_host_iommu_quirk_bypass_ro(VFIODevice *vbasedev,
>> uint32_t type, void *caps,
>> uint32_t size)
>> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
>> index 96735f1fc8..9605bf73b7 100644
>> --- a/hw/vfio/iommufd.c
>> +++ b/hw/vfio/iommufd.c
>> @@ -354,6 +354,7 @@ static bool
>iommufd_cdev_autodomains_get(VFIODevice *vbasedev,
>> VendorCaps caps;
>> VFIOIOASHwpt *hwpt;
>> uint32_t hwpt_id;
>> + uint8_t max_pasid_log2;
>
>I think this should be initialized to some default value.
OK, will add max_pasid_log2 = 0;
>
>> int ret;
>>
>> /* Try to find a domain */
>> @@ -398,7 +399,7 @@ static bool
>iommufd_cdev_autodomains_get(VFIODevice *vbasedev,
>> */
>> if (!iommufd_backend_get_device_info(vbasedev->iommufd, vbasedev-
>>devid,
>> &type, &caps, sizeof(caps),
>> &hw_caps,
>> - NULL, errp)) {
>> + &max_pasid_log2, errp)) {
>> return false;
>> }
>>
>> @@ -420,6 +421,11 @@ static bool
>iommufd_cdev_autodomains_get(VFIODevice *vbasedev,
>> }
>> }
>>
>> + if (max_pasid_log2 &&
>> + vfio_device_get_viommu_flags_pasid_supported(vbasedev)) {
>
>Can an IOMMU backend not support PASID while the vIOMMU device does ?
>That would be a problem no ?
If IOMMU backend doesn't support PASID, max_pasid_log2 will be 0 returned by
get_device_info().
Then QEMU will not expose vPASID capability of VFIO device to guest, then guest
cannot enable PASID on this VFIO device even though vIOMMU support PASID.
Thanks
Zhenzhong
>
>> + flags |= IOMMU_HWPT_ALLOC_PASID;
>> + }
>> +
>> if (cpr_is_incoming()) {
>> hwpt_id = vbasedev->cpr.hwpt_id;
>> goto skip_alloc;
