[SRU][jammy:linux-azure][PATCH v2 4/4] swiotlb: Honour dma_alloc_coherent() alignment in swiotlb_alloc()

[John Cabaj]

From: Will Deacon <will at kernel.org>

BugLink: https://bugs.launchpad.net/bugs/2096813

core-api/dma-api-howto.rst states the following properties of
dma_alloc_coherent():

  | The CPU virtual address and the DMA address are both guaranteed to
  | be aligned to the smallest PAGE_SIZE order which is greater than or
  | equal to the requested size.

However, swiotlb_alloc() passes zero for the 'alloc_align_mask'
parameter of swiotlb_find_slots() and so this property is not upheld.
Instead, allocations larger than a page are aligned to PAGE_SIZE,

Calculate the mask corresponding to the page order suitable for holding
the allocation and pass that to swiotlb_find_slots().

Fixes: e81e99bacc9f ("swiotlb: Support aligned swiotlb buffers")
Signed-off-by: Will Deacon <will at kernel.org>
Reviewed-by: Michael Kelley <mhklinux at outlook.com>
Reviewed-by: Petr Tesarik <petr.tesarik1 at huawei-partners.com>
Tested-by: Nicolin Chen <nicolinc at nvidia.com>
Tested-by: Michael Kelley <mhklinux at outlook.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
(backported picked from commit cbf53074a528191df82b4dba1e3d21191102255e)
[john-cabaj: upstream includes pool parameter as of the 6.6 kernel, so
removing context here]
Signed-off-by: John Cabaj <john.cabaj at canonical.com>
---
 kernel/dma/swiotlb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 79d09e8f2032..790e41ea875c 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -843,12 +843,14 @@ struct page *swiotlb_alloc(struct device *dev, size_t size)
 {
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
 	phys_addr_t tlb_addr;
+	unsigned int align;
 	int index;
 
 	if (!mem)
 		return NULL;
 
-	index = swiotlb_find_slots(dev, 0, size);
+	align = (1 << (get_order(size) + PAGE_SHIFT)) - 1;
+	index = swiotlb_find_slots(dev, 0, size, align);
 	if (index == -1)
 		return NULL;
 
-- 
2.43.0