On Thu, Nov 20, 2025 at 08:04:37AM +0000, Tian, Kevin wrote:

...

From: Jason Gunthorpe jgg@nvidia.com Sent: Saturday, November 8, 2025 12:50 AM

+static int pfn_reader_fill_dmabuf(struct pfn_reader_dmabuf *dmabuf,

• 		  struct pfn_batch *batch,
  

• 		  unsigned long start_index,
  

• 		  unsigned long last_index)
  

+{

• unsigned long start = dmabuf->start_offset + start_index * PAGE_SIZE;
• /*

• * This works in PAGE_SIZE indexes, if the dmabuf is sliced and
  

• * starts/ends at a sub page offset then the batch to domain code will
  

• * adjust it.
  

• */
  

dmabuf->start_offset comes from pages->dmabuf.start, which is initialized as:

pages->dmabuf.start = start - start_byte;

so it's always page-aligned. Where is the sub-page offset coming from?

I need to go over this again to check it, this sub-page stuff is a bit convoluted. start_offset should include the sub page offset here..

...

@@ -1687,6 +1737,12 @@ static void __iopt_area_unfill_domain(struct iopt_area *area,

lockdep_assert_held(&pages->mutex);

• if (iopt_is_dmabuf(pages)) {

• iopt_area_unmap_domain_range(area, domain, start_index,
  

• 			     last_index);
  

• return;
  

• }

this belongs to patch3?

This is part of programming the domain with the dmabuf, the patch3 was about the revoke which is a slightly different topic though they are both similar.

Thanks, Jason