Re: [PATCH v5 17/29] iommufd: Add mmap interface

On Sat, May 17, 2025 at 08:21:34PM -0700, Nicolin Chen wrote:

+/*

• • Helpers for IOMMU driver to alloc/destroy an mmapable area for a structure.
• • To support an mmappable MMIO region, kernel driver must first register it to
• • iommufd core to allocate an @out_offset, in the context of an driver-struct
• • allocation (e.g. viommu_alloc op). Then, it should report to user space this
• • @out_offset and the @length of the MMIO region for mmap syscall.
• */

+#define iommufd_viommu_alloc_mmap(viommu, member, mmio, length, out_offset) \

• ({ \

• static_assert(__same_type(struct iommufd_viommu,               \
  

• 			  viommu->member));                    \
  

• static_assert(offsetof(typeof(*viommu), member.obj) == 0);     \
  

• _iommufd_alloc_mmap(viommu->member.ictx, &viommu->member.obj,  \
  

• 		    mmio, length, out_offset);                 \
  

• })

Why is this like this? It's weird, just

static inline int iommufd_alloc_viommu_mmap(struct iommufd_viommu *viommu, phys_addr_t mmio_addr, size_t length, unsigned long *offset);

+/* The vm_pgoff must be pre-allocated from mt_mmap, and given to user space */ +static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma) +{

• struct iommufd_ctx *ictx = filp->private_data;
• size_t length = vma->vm_end - vma->vm_start;
• struct iommufd_mmap *immap;
• int rc;
• if (!PAGE_ALIGNED(length))

• return -EINVAL;
  

• if (!(vma->vm_flags & VM_SHARED))

• return -EINVAL;
  

• if (vma->vm_flags & VM_EXEC)

• return -EPERM;
  

• /* vma->vm_pgoff carries an index to an mtree entry (immap) */
• immap = mtree_load(&ictx->mt_mmap, vma->vm_pgoff);
• if (!immap)

• return -ENXIO;
  

• /* Validate the vm_pgoff and length against the registered region */
• if (vma->vm_pgoff != immap->startp)

• return -ENXIO;
  

This check seems redundant

Jason