Re: [PATCH 5.15.y v3 1/1] xen/swiotlb: relax alignment requirements

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 85fcb57c983f423180ba6ec5d0034242da05cc54

WARNING: Author mismatch between patch and upstream commit:
Backport author: Harshvardhan Jha<harshvardhan.j.jha@oracle.com>
Commit author: Juergen Gross<jgross@suse.com>

Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.12.y | Present (different SHA1: 5a10af375347)
6.6.y | Present (different SHA1: 461d9e8acaa4)
6.1.y | Present (different SHA1: 099606a7b2d5)

Note: The patch differs from the upstream commit:
---
1:  85fcb57c983f4 ! 1:  d8109ab010afb xen/swiotlb: relax alignment requirements
    @@
      ## Metadata ##
    -Author: Juergen Gross <jgross@suse.com>
    +Author: Harshvardhan Jha <harshvardhan.j.jha@oracle.com>
     
      ## Commit message ##
         xen/swiotlb: relax alignment requirements
     
    +    [ Upstream commit 85fcb57c983f423180ba6ec5d0034242da05cc54 ]
    +
         When mapping a buffer for DMA via .map_page or .map_sg DMA operations,
         there is no need to check the machine frames to be aligned according
         to the mapped areas size. All what is needed in these cases is that the
    @@ Commit message
         xen_swiotlb_free_coherent() directly.
     
         Fixes: 9f40ec84a797 ("xen/swiotlb: add alignment check for dma buffers")
    -    Reported-by: Jan Vejvalka <jan.vejvalka@lfmotol.cuni.cz>
    -    Tested-by: Jan Vejvalka <jan.vejvalka@lfmotol.cuni.cz>
    -    Signed-off-by: Juergen Gross <jgross@suse.com>
    -    Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
    +
         Signed-off-by: Juergen Gross <jgross@suse.com>
    +    Signed-off-by: Harshvardhan Jha <harshvardhan.j.jha@oracle.com>
     
      ## drivers/xen/swiotlb-xen.c ##
     @@ drivers/xen/swiotlb-xen.c: static inline phys_addr_t xen_dma_to_phys(struct device *dev,
    @@ drivers/xen/swiotlb-xen.c: static inline phys_addr_t xen_dma_to_phys(struct devi
      	for (i = 1; i < nr_pages; i++)
      		if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
      			return 1;
    -@@ drivers/xen/swiotlb-xen.c: xen_swiotlb_alloc_coherent(struct device *dev, size_t size,
    - 
    - 	*dma_handle = xen_phys_to_dma(dev, phys);
    - 	if (*dma_handle + size - 1 > dma_mask ||
    --	    range_straddles_page_boundary(phys, size)) {
    -+	    range_straddles_page_boundary(phys, size) ||
    -+	    range_requires_alignment(phys, size)) {
    - 		if (xen_create_contiguous_region(phys, order, fls64(dma_mask),
    - 				dma_handle) != 0)
    - 			goto out_free_pages;
    -@@ drivers/xen/swiotlb-xen.c: xen_swiotlb_free_coherent(struct device *dev, size_t size, void *vaddr,
    - 	size = ALIGN(size, XEN_PAGE_SIZE);
    +@@ drivers/xen/swiotlb-xen.c: xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
    + 	phys = dma_to_phys(hwdev, *dma_handle);
    + 	dev_addr = xen_phys_to_dma(hwdev, phys);
    + 	if (((dev_addr + size - 1 <= dma_mask)) &&
    +-	    !range_straddles_page_boundary(phys, size))
    ++	    !range_straddles_page_boundary(phys, size) &&
    ++	    !range_requires_alignment(phys, size))
    + 		*dma_handle = dev_addr;
    + 	else {
    + 		if (xen_create_contiguous_region(phys, order,
    +@@ drivers/xen/swiotlb-xen.c: xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
      
    - 	if (WARN_ON_ONCE(dma_handle + size - 1 > dev->coherent_dma_mask) ||
    --	    WARN_ON_ONCE(range_straddles_page_boundary(phys, size)))
    -+	    WARN_ON_ONCE(range_straddles_page_boundary(phys, size) ||
    -+			 range_requires_alignment(phys, size)))
    - 	    	return;
    + 	if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
    + 		     range_straddles_page_boundary(phys, size)) &&
    ++	    !range_requires_alignment(phys, size) &&
    + 	    TestClearPageXenRemapped(page))
    + 		xen_destroy_contiguous_region(phys, order);
      
    - 	if (TestClearPageXenRemapped(virt_to_page(vaddr)))
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |