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What: /sys/bus/pci/drivers/uio_pci_sva/<pci_dev>/pasid
Date: September 2025
Contact: Yaxing Guo <guoyaxing@bosc.ac.cn>
Description:
Process Address Space ID (PASID) assigned by IOMMU driver to
the device for use with Shared Virtual Addressing (SVA).
This read-only attribute exposes the PASID (A 20-bit identifier
used in PCIe Address Translation Services and iommu table walks)
allocated by the IOMMU driver during sva device binding.
User-space UIO applications must read this attribute to obtain
the PASID and program it into the device's configuration registers.
This enables the device to perform DMA using user-space virtual
address, with address translation handled by IOMMU.
UIO User-space applications must:
- Opening device and Mapping the device's register space via /dev/uioX
(This triggers the IOMMU driver to allocate the PASID)
- Reading the PASID from sysfs
- Writing the PASID to a device-specific register (with example offset)
The code may be like:
map = mmap(..., "/dev/uio0", ...);
f = fopen("/sys/.../pasid", "r");
fscanf(f, "%d", &pasid);
map[REG_PASID_OFFSET] = pasid;
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