[PATCH v3] powerpc/iommu: DMA address offset is incorrectly calculated with 2MB TCEs

[PATCH v3] powerpc/iommu: DMA address offset is incorrectly calculated with 2MB TCEs

[Gaurav Batra]

When DMA window is backed by 2MB TCEs, the DMA address for the mapped
page should be the offset of the page relative to the 2MB TCE. The code
was incorrectly setting the DMA address to the beginning of the TCE
range.

Mellanox driver is reporting timeout trying to ENABLE_HCA for an SR-IOV
ethernet port, when DMA window is backed by 2MB TCEs.

Fixes: 387273118714 ("powerps/pseries/dma: Add support for 2M IOMMU page size")

Signed-off-by: Gaurav Batra <gbatra@linux.vnet.ibm.com>

Reviewed-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/iommu.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index ee95937bdaf1..b8b7a189cd3c 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -517,7 +517,7 @@ int ppc_iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 		/* Convert entry to a dma_addr_t */
 		entry += tbl->it_offset;
 		dma_addr = entry << tbl->it_page_shift;
-		dma_addr |= (s->offset & ~IOMMU_PAGE_MASK(tbl));
+		dma_addr |= (vaddr & ~IOMMU_PAGE_MASK(tbl));
 
 		DBG("  - %lu pages, entry: %lx, dma_addr: %lx\n",
 			    npages, entry, dma_addr);
@@ -904,6 +904,7 @@ void *iommu_alloc_coherent(struct device *dev, struct iommu_table *tbl,
 	unsigned int order;
 	unsigned int nio_pages, io_order;
 	struct page *page;
+	int tcesize = (1 << tbl->it_page_shift);
 
 	size = PAGE_ALIGN(size);
 	order = get_order(size);
@@ -930,7 +931,8 @@ void *iommu_alloc_coherent(struct device *dev, struct iommu_table *tbl,
 	memset(ret, 0, size);
 
 	/* Set up tces to cover the allocated range */
-	nio_pages = size >> tbl->it_page_shift;
+	nio_pages = IOMMU_PAGE_ALIGN(size, tbl) >> tbl->it_page_shift;
+
 	io_order = get_iommu_order(size, tbl);
 	mapping = iommu_alloc(dev, tbl, ret, nio_pages, DMA_BIDIRECTIONAL,
 			      mask >> tbl->it_page_shift, io_order, 0);
@@ -938,7 +940,8 @@ void *iommu_alloc_coherent(struct device *dev, struct iommu_table *tbl,
 		free_pages((unsigned long)ret, order);
 		return NULL;
 	}
-	*dma_handle = mapping;
+
+	*dma_handle = mapping | ((u64)ret & (tcesize - 1));
 	return ret;
 }
 
@@ -949,7 +952,7 @@ void iommu_free_coherent(struct iommu_table *tbl, size_t size,
 		unsigned int nio_pages;
 
 		size = PAGE_ALIGN(size);
-		nio_pages = size >> tbl->it_page_shift;
+		nio_pages = IOMMU_PAGE_ALIGN(size, tbl) >> tbl->it_page_shift;
 		iommu_free(tbl, dma_handle, nio_pages);
 		size = PAGE_ALIGN(size);
 		free_pages((unsigned long)vaddr, get_order(size));
-- 

Re: [PATCH v3] powerpc/iommu: DMA address offset is incorrectly calculated with 2MB TCEs

[Srikar Dronamraju]

* Gaurav Batra <gbatra@linux.vnet.ibm.com> [2023-05-04 12:59:13]:

> When DMA window is backed by 2MB TCEs, the DMA address for the mapped
> page should be the offset of the page relative to the 2MB TCE. The code
> was incorrectly setting the DMA address to the beginning of the TCE
> range.
> 
> Mellanox driver is reporting timeout trying to ENABLE_HCA for an SR-IOV
> ethernet port, when DMA window is backed by 2MB TCEs.
> 
> Fixes: 387273118714 ("powerps/pseries/dma: Add support for 2M IOMMU page size")
> 
> Signed-off-by: Gaurav Batra <gbatra@linux.vnet.ibm.com>
> 

Works with this patch.
Tested-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>

> Reviewed-by: Greg Joyce <gjoyce@linux.vnet.ibm.com>
> Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
> ---

-- 
Thanks and Regards
Srikar Dronamraju

Re: [PATCH v3] powerpc/iommu: DMA address offset is incorrectly calculated with 2MB TCEs

[Michael Ellerman]

On Thu, 04 May 2023 12:59:13 -0500, Gaurav Batra wrote:
> When DMA window is backed by 2MB TCEs, the DMA address for the mapped
> page should be the offset of the page relative to the 2MB TCE. The code
> was incorrectly setting the DMA address to the beginning of the TCE
> range.
> 
> Mellanox driver is reporting timeout trying to ENABLE_HCA for an SR-IOV
> ethernet port, when DMA window is backed by 2MB TCEs.
> 
> [...]

Applied to powerpc/fixes.

[1/1] powerpc/iommu: DMA address offset is incorrectly calculated with 2MB TCEs
      https://git.kernel.org/powerpc/c/096339ab84f36beae0b1db25e0ce63fb3873e8b2

cheers