RE: [RFC 3/7] iommufd: Add iommufd_device_bind_pasid()

From: Liu, Yi L yi.l.liu@intel.com Sent: Monday, October 9, 2023 4:51 PM

+struct iommufd_device *iommufd_device_bind_pasid(struct iommufd_ctx *ictx,

• 				 struct device *dev,
  

• 				 u32 pasid, u32 *id)
  

+{

• struct iommufd_device *idev;
• int rc;
• /*

• * iommufd always sets IOMMU_CACHE because we offer no way for
  

userspace

• * to restore cache coherency.
  

• */
  

• if (!device_iommu_capable(dev, IOMMU_CAP_CACHE_COHERENCY))

• return ERR_PTR(-EINVAL);
  

• /*

• * No iommu supports pasid-granular msi message today. Here we
  

• * just check whether the parent device can do safe interrupts.
  

• * Isolation between virtual devices within the parent device
  

• * relies on the parent driver to enforce.
  

• */
  

• if (!iommufd_selftest_is_mock_dev(dev) &&

•    !msi_device_has_isolated_msi(dev)) {
  

• rc = iommufd_allow_unsafe_interrupts(dev);
  

• if (rc)
  

• 	return ERR_PTR(rc);
  

• }

Only MemWr w/o pasid can be interpreted as an interrupt message then we need msi isolation to protect.

But for SIOV all MemWr's are tagged with a pasid hence can never trigger an interrupt. From this angle looks this check is unnecessary.