On Mon, Apr 28, 2025 at 12:41:33AM +0000, Tian, Kevin wrote:
From: Baolu Lu baolu.lu@linux.intel.com Sent: Sunday, April 27, 2025 2:24 PM
On 4/26/25 13:57, Nicolin Chen wrote:
@@ -120,6 +128,13 @@ struct iommufd_viommu {
array->entry_num to report the number of handled requests.The data structure of the array entry must be defined ininclude/uapi/linux/iommufd.h
- @vdevice_alloc: Allocate a vDEVICE object and init its driver-level
structure
or HW procedure. Note that the core-level structure is filled
by the iommufd core after calling this op. @virt_id carries a
per-vIOMMU virtual ID for the driver to initialize its HW.I'm wondering whether the 'per-vIOMMU virtual ID' is intended to be generic for other features that might require a vdevice. I'm also not sure where this virtual ID originates when I read it here. Could it
for PCI it's the virtual BDF in the guest PCI topology, hence provided by the VMM when calling @vdevice_alloc:
The "virtual ID" here can, but not necessarily always, be BDF.
Jason had remarks when we added the ioctl: https://lore.kernel.org/linux-iommu/20241004114147.GF1365916@nvidia.com/
And uAPI kdoc (include/uapi/linux/iommufd.h) has its description: /** * struct iommu_vdevice_alloc - ioctl(IOMMU_VDEVICE_ALLOC) ... * @virt_id: Virtual device ID per vIOMMU, e.g. vSID of ARM SMMUv3, vDeviceID * of AMD IOMMU, and vRID of a nested Intel VT-d to a Context Table
So, yes, here we are just forwarding that from the ioctl to viommu op. Perhaps I should add a line here: * @vdevice_alloc: Allocate a vDEVICE object and init its driver-level * or HW procedure. Note that the core-level structure is filled * by the iommufd core after calling this op. @virt_id carries a * per-vIOMMU virtual ID (refer to struct iommu_vdevice_alloc in * include/uapi/linux/iommufd.h) for the driver to initialize its * HW for an attached physical device.
Thanks Nicolin