[PATCH v6 13/25] iommufd: Add mmap interface
Nicolin Chen
nicolinc at nvidia.com
Wed Jun 25 14:18:19 PDT 2025
On Mon, Jun 16, 2025 at 11:13:19AM -0300, Jason Gunthorpe wrote:
> On Sat, Jun 14, 2025 at 12:14:38AM -0700, Nicolin Chen wrote:
>
> > +/* Entry for iommufd_ctx::mt_mmap */
> > +struct iommufd_mmap {
> > + struct iommufd_object *owner;
> > +
> > + /* Allocated start position in mt_mmap tree */
> > + unsigned long startp;
>
> pgoff_t, looks like this is already in PAGE_SIZE units.
>
> > + /* Physical range for io_remap_pfn_range() */
> > + unsigned long mmio_pfn;
>
> physaddr_t and maybe don't use pfn?
>
> > + unsigned long num_pfns;
>
> size_t
I made the following changes, though I kept "unsigned long" for
"vm_pgoff" aligning with vma->vm_pgoff:
diff --git a/drivers/iommu/iommufd/driver.c b/drivers/iommu/iommufd/driver.c
index d797b77e878c6..73fcf3a89bf82 100644
--- a/drivers/iommu/iommufd/driver.c
+++ b/drivers/iommu/iommufd/driver.c
@@ -53,19 +53,19 @@ int _iommufd_alloc_mmap(struct iommufd_ctx *ictx, struct iommufd_object *owner,
if (!immap)
return -ENOMEM;
immap->owner = owner;
- immap->num_pfns = length >> PAGE_SHIFT;
- immap->mmio_pfn = mmio_addr >> PAGE_SHIFT;
+ immap->length = length;
+ immap->mmio_addr = mmio_addr;
- rc = mtree_alloc_range(&ictx->mt_mmap, &startp, immap, immap->num_pfns,
- 0, U32_MAX >> PAGE_SHIFT, GFP_KERNEL);
+ rc = mtree_alloc_range(&ictx->mt_mmap, &startp, immap, immap->length,
+ 0, PHYS_ADDR_MAX, GFP_KERNEL);
if (rc < 0) {
kfree(immap);
return rc;
}
- immap->startp = startp;
- /* mmap() syscall will right-shift the offset in vma->vm_pgoff */
- *offset = startp << PAGE_SHIFT;
+ /* mmap() syscall will right-shift the offset in vma->vm_pgoff too */
+ immap->vm_pgoff = startp >> PAGE_SHIFT;
+ *offset = startp;
return 0;
}
EXPORT_SYMBOL_NS_GPL(_iommufd_alloc_mmap, "IOMMUFD");
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index cc9088ba5c812..ebac6a4b3538c 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -61,12 +61,12 @@ struct iommufd_ctx {
struct iommufd_mmap {
struct iommufd_object *owner;
- /* Allocated start position in mt_mmap tree */
- unsigned long startp;
+ /* Page-shifted start position in mt_mmap to validate vma->vm_pgoff */
+ unsigned long vm_pgoff;
/* Physical range for io_remap_pfn_range() */
- unsigned long mmio_pfn;
- unsigned long num_pfns;
+ phys_addr_t mmio_addr;
+ size_t length;
};
/*
diff --git a/drivers/iommu/iommufd/main.c b/drivers/iommu/iommufd/main.c
index 339a269ebbc81..0fb81a905cb13 100644
--- a/drivers/iommu/iommufd/main.c
+++ b/drivers/iommu/iommufd/main.c
@@ -514,17 +514,15 @@ static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma)
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);
+ /* vma->vm_pgoff carries a page-shifted start position to an immap */
+ immap = mtree_load(&ictx->mt_mmap, vma->vm_pgoff << PAGE_SHIFT);
if (!immap)
return -ENXIO;
/*
- * mtree_load() returns the immap for any contained pgoff, only allow
- * the immap thing to be mapped
+ * mtree_load() returns the immap for any contained mmio_addr, so only
+ * allow the exact immap thing to be mapped
*/
- if (vma->vm_pgoff != immap->startp)
- return -ENXIO;
- if (length != immap->num_pfns << PAGE_SHIFT)
+ if (vma->vm_pgoff != immap->vm_pgoff || length != immap->length)
return -ENXIO;
vma->vm_pgoff = 0;
@@ -532,7 +530,8 @@ static int iommufd_fops_mmap(struct file *filp, struct vm_area_struct *vma)
vma->vm_ops = &iommufd_vma_ops;
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
- rc = io_remap_pfn_range(vma, vma->vm_start, immap->mmio_pfn, length,
+ rc = io_remap_pfn_range(vma, vma->vm_start,
+ immap->mmio_addr >> PAGE_SHIFT, length,
vma->vm_page_prot);
if (rc)
return rc;
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