Merge tag 'for-linus-iommufd' of git://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd

Pull iommufd updates from Jason Gunthorpe:
 "This is a pretty consequential cycle for iommufd, though this pull is
  not too big. It is based on a shared branch with VFIO that introduces
  VFIO_DEVICE_FEATURE_DMA_BUF a DMABUF exporter for VFIO device's MMIO
  PCI BARs. This was a large multiple series journey over the last year
  and a half.

  Based on that work IOMMUFD gains support for VFIO DMABUF's in its
  existing IOMMU_IOAS_MAP_FILE, which closes the last major gap to
  support PCI peer to peer transfers within VMs.

  In Joerg's iommu tree we have the "generic page table" work which aims
  to consolidate all the duplicated page table code in every iommu
  driver into a single algorithm. This will be used by iommufd to
  implement unique page table operations to start adding new features
  and improve performance.

  In here:

   - Expand IOMMU_IOAS_MAP_FILE to accept a DMABUF exported from VFIO.
     This is the first step to broader DMABUF support in iommufd, right
     now it only works with VFIO. This closes the last functional gap
     with classic VFIO type 1 to safely support PCI peer to peer DMA by
     mapping the VFIO device's MMIO into the IOMMU.

   - Relax SMMUv3 restrictions on nesting domains to better support
     qemu's sequence to have an identity mapping before the vSID is
     established"

* tag 'for-linus-iommufd' of git://git.kernel.org/pub/scm/linux/kernel/git/jgg/iommufd:
  iommu/arm-smmu-v3-iommufd: Allow attaching nested domain for GBPA cases
  iommufd/selftest: Add some tests for the dmabuf flow
  iommufd: Accept a DMABUF through IOMMU_IOAS_MAP_FILE
  iommufd: Have iopt_map_file_pages convert the fd to a file
  iommufd: Have pfn_reader process DMABUF iopt_pages
  iommufd: Allow MMIO pages in a batch
  iommufd: Allow a DMABUF to be revoked
  iommufd: Do not map/unmap revoked DMABUFs
  iommufd: Add DMABUF to iopt_pages
  vfio/pci: Add vfio_pci_dma_buf_iommufd_map()

2 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index 336a0e58b443..706877f998ff 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -29,6 +29,7 @@ struct vfio_pci_core_device;
 struct vfio_pci_region;
 struct p2pdma_provider;
 struct dma_buf_phys_vec;
+struct dma_buf_attachment;
 
 struct vfio_pci_eventfd {
 	struct eventfd_ctx	*ctx;
@@ -226,4 +227,7 @@ static inline bool is_aligned_for_order(struct vm_area_struct *vma,
 			   !IS_ALIGNED(pfn, 1 << order)));
 }
 
+int vfio_pci_dma_buf_iommufd_map(struct dma_buf_attachment *attachment,
+				 struct dma_buf_phys_vec *phys);
+
 #endif /* VFIO_PCI_CORE_H */
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index c218c89e0e2e..2c41920b641d 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -450,6 +450,16 @@ struct iommu_hwpt_vtd_s1 {
  * nested domain will translate the same as the nesting parent. The S1 will
  * install a Context Descriptor Table pointing at userspace memory translated
  * by the nesting parent.
+ *
+ * It's suggested to allocate a vDEVICE object carrying vSID and then re-attach
+ * the nested domain, as soon as the vSID is available in the VMM level:
+ *
+ * - when Cfg=translate, a vDEVICE must be allocated prior to attaching to the
+ *   allocated nested domain, as CD/ATS invalidations and vevents need a vSID.
+ * - when Cfg=bypass/abort, a vDEVICE is not enforced during the nested domain
+ *   attachment, to support a GBPA case where VM sets CR0.SMMUEN=0. However, if
+ *   VM sets CR0.SMMUEN=1 while missing a vDEVICE object, kernel would fail to
+ *   report events to the VM. E.g. F_TRANSLATION when guest STE.Cfg=abort.
  */
 struct iommu_hwpt_arm_smmuv3 {
 	__aligned_le64 ste[2];