[PATCH v2 0/2] DMA IOMMU static calls

[PATCH v2 0/2] DMA IOMMU static calls

[Leon Romanovsky]

Changelog:
v2:
 * Ditched dma_ops flag in favor of field in struct device (suggested by Christoph)
 * Removed CONFIG_DMA_OPS select from dma-iommu.c Kconfig
 * Removed flags field which exist only in default IOMMU
v1: https://lore.kernel.org/all/cover.1721041611.git.leon@kernel.org/
 * Dropped extra layer and called directly to iommu_dma_* functions
 * Added unmap_page and unmap_sg to dummy ops
 * Converted all dma-mapping calls to use iommu directly
 * Updated commit messages
v0: https://lore.kernel.org/all/98d1821780028434ff55b5d2f1feea287409fbc4.1720693745.git.leon@kernel.org/

Leon Romanovsky (2):
  dma: call unconditionally to unmap_page and unmap_sg callbacks
  dma: add IOMMU static calls with clear default ops

 MAINTAINERS                 |   1 +
 drivers/iommu/Kconfig       |   1 -
 drivers/iommu/dma-iommu.c   | 117 ++++++++++---------------
 include/linux/device.h      |   3 +
 include/linux/dma-map-ops.h |  13 ---
 include/linux/iommu-dma.h   | 169 ++++++++++++++++++++++++++++++++++++
 kernel/dma/dummy.c          |  21 +++++
 kernel/dma/mapping.c        |  88 ++++++++++++++++---
 8 files changed, 315 insertions(+), 98 deletions(-)
 create mode 100644 include/linux/iommu-dma.h

-- 
2.45.2

[PATCH v2 1/2] dma: call unconditionally to unmap_page and unmap_sg callbacks

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Almost all users of ->map_page()/map_sg() callbacks implement
->unmap_page()/unmap_sg() callbacks too. One user which doesn't do it,
is dummy DMA ops interface, and the use of this interface is to fail
the operation and in such case, there won't be any call to
->unmap_page()/unmap_sg().

This patch removes the existence checks of ->unmap_page()/unmap_sg()
and calls to it directly to create symmetrical interface to
->map_page()/map_sg().

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
---
 kernel/dma/dummy.c   | 21 +++++++++++++++++++++
 kernel/dma/mapping.c |  4 ++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/dummy.c b/kernel/dma/dummy.c
index b492d59ac77e..92de80e5b057 100644
--- a/kernel/dma/dummy.c
+++ b/kernel/dma/dummy.c
@@ -17,6 +17,15 @@ static dma_addr_t dma_dummy_map_page(struct device *dev, struct page *page,
 {
 	return DMA_MAPPING_ERROR;
 }
+static void dma_dummy_unmap_page(struct device *dev, dma_addr_t dma_handle,
+		size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+	/*
+	 * Dummy ops doesn't support map_page, so unmap_page should never be
+	 * called.
+	 */
+	WARN_ON_ONCE(true);
+}
 
 static int dma_dummy_map_sg(struct device *dev, struct scatterlist *sgl,
 		int nelems, enum dma_data_direction dir,
@@ -25,6 +34,16 @@ static int dma_dummy_map_sg(struct device *dev, struct scatterlist *sgl,
 	return -EINVAL;
 }
 
+static void dma_dummy_unmap_sg(struct device *dev, struct scatterlist *sgl,
+		int nelems, enum dma_data_direction dir,
+		unsigned long attrs)
+{
+	/*
+	 * Dummy ops doesn't support map_sg, so unmap_sg should never be called.
+	 */
+	WARN_ON_ONCE(true);
+}
+
 static int dma_dummy_supported(struct device *hwdev, u64 mask)
 {
 	return 0;
@@ -33,6 +52,8 @@ static int dma_dummy_supported(struct device *hwdev, u64 mask)
 const struct dma_map_ops dma_dummy_ops = {
 	.mmap                   = dma_dummy_mmap,
 	.map_page               = dma_dummy_map_page,
+	.unmap_page             = dma_dummy_unmap_page,
 	.map_sg                 = dma_dummy_map_sg,
+	.unmap_sg               = dma_dummy_unmap_sg,
 	.dma_supported          = dma_dummy_supported,
 };
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 81de84318ccc..6832fd6f0796 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -177,7 +177,7 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 	if (dma_map_direct(dev, ops) ||
 	    arch_dma_unmap_page_direct(dev, addr + size))
 		dma_direct_unmap_page(dev, addr, size, dir, attrs);
-	else if (ops->unmap_page)
+	else
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	debug_dma_unmap_page(dev, addr, size, dir);
 }
@@ -291,7 +291,7 @@ void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
 	if (dma_map_direct(dev, ops) ||
 	    arch_dma_unmap_sg_direct(dev, sg, nents))
 		dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
-	else if (ops->unmap_sg)
+	else
 		ops->unmap_sg(dev, sg, nents, dir, attrs);
 }
 EXPORT_SYMBOL(dma_unmap_sg_attrs);
-- 
2.45.2

[PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Most of the arch DMA ops (which often, but not  always, involve
some sort of IOMMU) are using the same DMA operations. These DMA
operations are default ones implemented in drivers/iomem/dma-iommu.c.

So let's make sure to call them directly without need to perform function
pointers dereference.

During system initialization, the arch can set its own DMA and in such case,
the default DMA operations will be overridden.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
---
 MAINTAINERS                 |   1 +
 drivers/iommu/Kconfig       |   1 -
 drivers/iommu/dma-iommu.c   | 117 ++++++++++---------------
 include/linux/device.h      |   3 +
 include/linux/dma-map-ops.h |  13 ---
 include/linux/iommu-dma.h   | 169 ++++++++++++++++++++++++++++++++++++
 kernel/dma/mapping.c        |  84 +++++++++++++++---
 7 files changed, 292 insertions(+), 96 deletions(-)
 create mode 100644 include/linux/iommu-dma.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 958e935449e5..ce06c4df7e05 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11525,6 +11525,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/iommu/linux.git
 F:	Documentation/devicetree/bindings/iommu/
 F:	Documentation/userspace-api/iommu.rst
 F:	drivers/iommu/
+F:	include/linux/iommu-dma.h
 F:	include/linux/iommu.h
 F:	include/linux/iova.h
 F:	include/linux/of_iommu.h
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index c04584be3089..e0dd30c1b08a 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -151,7 +151,6 @@ config OF_IOMMU
 # IOMMU-agnostic DMA-mapping layer
 config IOMMU_DMA
 	def_bool ARM64 || X86 || S390
-	select DMA_OPS
 	select IOMMU_API
 	select IOMMU_IOVA
 	select IRQ_MSI_IOMMU
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 43520e7275cc..174b84f9cd92 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -17,6 +17,7 @@
 #include <linux/gfp.h>
 #include <linux/huge_mm.h>
 #include <linux/iommu.h>
+#include <linux/iommu-dma.h>
 #include <linux/iova.h>
 #include <linux/irq.h>
 #include <linux/list_sort.h>
@@ -1039,9 +1040,9 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
 	return NULL;
 }
 
-static struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev,
-		size_t size, enum dma_data_direction dir, gfp_t gfp,
-		unsigned long attrs)
+struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev, size_t size,
+					       enum dma_data_direction dir,
+					       gfp_t gfp, unsigned long attrs)
 {
 	struct dma_sgt_handle *sh;
 
@@ -1058,8 +1059,9 @@ static struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev,
 	return &sh->sgt;
 }
 
-static void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
-		struct sg_table *sgt, enum dma_data_direction dir)
+void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
+				  struct sg_table *sgt,
+				  enum dma_data_direction dir)
 {
 	struct dma_sgt_handle *sh = sgt_handle(sgt);
 
@@ -1069,8 +1071,8 @@ static void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
 	kfree(sh);
 }
 
-static void iommu_dma_sync_single_for_cpu(struct device *dev,
-		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
+void iommu_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
+				   size_t size, enum dma_data_direction dir)
 {
 	phys_addr_t phys;
 
@@ -1085,8 +1087,8 @@ static void iommu_dma_sync_single_for_cpu(struct device *dev,
 		swiotlb_sync_single_for_cpu(dev, phys, size, dir);
 }
 
-static void iommu_dma_sync_single_for_device(struct device *dev,
-		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
+void iommu_dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle,
+				      size_t size, enum dma_data_direction dir)
 {
 	phys_addr_t phys;
 
@@ -1101,9 +1103,8 @@ static void iommu_dma_sync_single_for_device(struct device *dev,
 		arch_sync_dma_for_device(phys, size, dir);
 }
 
-static void iommu_dma_sync_sg_for_cpu(struct device *dev,
-		struct scatterlist *sgl, int nelems,
-		enum dma_data_direction dir)
+void iommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+			       int nelems, enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;
@@ -1117,9 +1118,8 @@ static void iommu_dma_sync_sg_for_cpu(struct device *dev,
 			arch_sync_dma_for_cpu(sg_phys(sg), sg->length, dir);
 }
 
-static void iommu_dma_sync_sg_for_device(struct device *dev,
-		struct scatterlist *sgl, int nelems,
-		enum dma_data_direction dir)
+void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
+				  int nelems, enum dma_data_direction dir)
 {
 	struct scatterlist *sg;
 	int i;
@@ -1134,9 +1134,9 @@ static void iommu_dma_sync_sg_for_device(struct device *dev,
 			arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
 }
 
-static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
-		unsigned long offset, size_t size, enum dma_data_direction dir,
-		unsigned long attrs)
+dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
+			      unsigned long offset, size_t size,
+			      enum dma_data_direction dir, unsigned long attrs)
 {
 	phys_addr_t phys = page_to_phys(page) + offset;
 	bool coherent = dev_is_dma_coherent(dev);
@@ -1194,8 +1194,9 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
 	return iova;
 }
 
-static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
-		size_t size, enum dma_data_direction dir, unsigned long attrs)
+void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
+			  size_t size, enum dma_data_direction dir,
+			  unsigned long attrs)
 {
 	struct iommu_domain *domain = iommu_get_dma_domain(dev);
 	phys_addr_t phys;
@@ -1348,8 +1349,8 @@ static int iommu_dma_map_sg_swiotlb(struct device *dev, struct scatterlist *sg,
  * impedance-matching, to be able to hand off a suitably-aligned list,
  * but still preserve the original offsets and sizes for the caller.
  */
-static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
-		int nents, enum dma_data_direction dir, unsigned long attrs)
+int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
+		     enum dma_data_direction dir, unsigned long attrs)
 {
 	struct iommu_domain *domain = iommu_get_dma_domain(dev);
 	struct iommu_dma_cookie *cookie = domain->iova_cookie;
@@ -1468,8 +1469,8 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
 	return ret;
 }
 
-static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
-		int nents, enum dma_data_direction dir, unsigned long attrs)
+void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
+			enum dma_data_direction dir, unsigned long attrs)
 {
 	dma_addr_t end = 0, start;
 	struct scatterlist *tmp;
@@ -1518,16 +1519,18 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
 		__iommu_dma_unmap(dev, start, end - start);
 }
 
-static dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
-		size_t size, enum dma_data_direction dir, unsigned long attrs)
+dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
+				  size_t size, enum dma_data_direction dir,
+				  unsigned long attrs)
 {
 	return __iommu_dma_map(dev, phys, size,
 			dma_info_to_prot(dir, false, attrs) | IOMMU_MMIO,
 			dma_get_mask(dev));
 }
 
-static void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
-		size_t size, enum dma_data_direction dir, unsigned long attrs)
+void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
+			      size_t size, enum dma_data_direction dir,
+			      unsigned long attrs)
 {
 	__iommu_dma_unmap(dev, handle, size);
 }
@@ -1563,8 +1566,8 @@ static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
 		dma_free_contiguous(dev, page, alloc_size);
 }
 
-static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
-		dma_addr_t handle, unsigned long attrs)
+void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
+		    dma_addr_t handle, unsigned long attrs)
 {
 	__iommu_dma_unmap(dev, handle, size);
 	__iommu_dma_free(dev, size, cpu_addr);
@@ -1607,8 +1610,8 @@ static void *iommu_dma_alloc_pages(struct device *dev, size_t size,
 	return NULL;
 }
 
-static void *iommu_dma_alloc(struct device *dev, size_t size,
-		dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
+void *iommu_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
+		      gfp_t gfp, unsigned long attrs)
 {
 	bool coherent = dev_is_dma_coherent(dev);
 	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
@@ -1642,9 +1645,9 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
 	return cpu_addr;
 }
 
-static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
-		void *cpu_addr, dma_addr_t dma_addr, size_t size,
-		unsigned long attrs)
+int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+		   void *cpu_addr, dma_addr_t dma_addr, size_t size,
+		   unsigned long attrs)
 {
 	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
 	unsigned long pfn, off = vma->vm_pgoff;
@@ -1673,9 +1676,9 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 			       vma->vm_page_prot);
 }
 
-static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
-		void *cpu_addr, dma_addr_t dma_addr, size_t size,
-		unsigned long attrs)
+int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
+			  void *cpu_addr, dma_addr_t dma_addr, size_t size,
+			  unsigned long attrs)
 {
 	struct page *page;
 	int ret;
@@ -1700,19 +1703,19 @@ static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
 	return ret;
 }
 
-static unsigned long iommu_dma_get_merge_boundary(struct device *dev)
+unsigned long iommu_dma_get_merge_boundary(struct device *dev)
 {
 	struct iommu_domain *domain = iommu_get_dma_domain(dev);
 
 	return (1UL << __ffs(domain->pgsize_bitmap)) - 1;
 }
 
-static size_t iommu_dma_opt_mapping_size(void)
+size_t iommu_dma_opt_mapping_size(void)
 {
 	return iova_rcache_range();
 }
 
-static size_t iommu_dma_max_mapping_size(struct device *dev)
+size_t iommu_dma_max_mapping_size(struct device *dev)
 {
 	if (dev_is_untrusted(dev))
 		return swiotlb_max_mapping_size(dev);
@@ -1720,32 +1723,6 @@ static size_t iommu_dma_max_mapping_size(struct device *dev)
 	return SIZE_MAX;
 }
 
-static const struct dma_map_ops iommu_dma_ops = {
-	.flags			= DMA_F_PCI_P2PDMA_SUPPORTED |
-				  DMA_F_CAN_SKIP_SYNC,
-	.alloc			= iommu_dma_alloc,
-	.free			= iommu_dma_free,
-	.alloc_pages_op		= dma_common_alloc_pages,
-	.free_pages		= dma_common_free_pages,
-	.alloc_noncontiguous	= iommu_dma_alloc_noncontiguous,
-	.free_noncontiguous	= iommu_dma_free_noncontiguous,
-	.mmap			= iommu_dma_mmap,
-	.get_sgtable		= iommu_dma_get_sgtable,
-	.map_page		= iommu_dma_map_page,
-	.unmap_page		= iommu_dma_unmap_page,
-	.map_sg			= iommu_dma_map_sg,
-	.unmap_sg		= iommu_dma_unmap_sg,
-	.sync_single_for_cpu	= iommu_dma_sync_single_for_cpu,
-	.sync_single_for_device	= iommu_dma_sync_single_for_device,
-	.sync_sg_for_cpu	= iommu_dma_sync_sg_for_cpu,
-	.sync_sg_for_device	= iommu_dma_sync_sg_for_device,
-	.map_resource		= iommu_dma_map_resource,
-	.unmap_resource		= iommu_dma_unmap_resource,
-	.get_merge_boundary	= iommu_dma_get_merge_boundary,
-	.opt_mapping_size	= iommu_dma_opt_mapping_size,
-	.max_mapping_size       = iommu_dma_max_mapping_size,
-};
-
 void iommu_setup_dma_ops(struct device *dev)
 {
 	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
@@ -1756,10 +1733,10 @@ void iommu_setup_dma_ops(struct device *dev)
 	if (iommu_is_dma_domain(domain)) {
 		if (iommu_dma_init_domain(domain, dev))
 			goto out_err;
-		dev->dma_ops = &iommu_dma_ops;
-	} else if (dev->dma_ops == &iommu_dma_ops) {
+		dev->dma_iommu = true;
+	} else if (dev->dma_iommu) {
 		/* Clean up if we've switched *from* a DMA domain */
-		dev->dma_ops = NULL;
+		dev->dma_iommu = false;
 	}
 
 	return;
diff --git a/include/linux/device.h b/include/linux/device.h
index ace039151cb8..7fa1e40b617a 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -822,6 +822,9 @@ struct device {
 #ifdef CONFIG_DMA_NEED_SYNC
 	bool			dma_skip_sync:1;
 #endif
+#ifdef CONFIG_IOMMU_DMA
+	bool			dma_iommu : 1;
+#endif
 };
 
 /**
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 02a1c825896b..077b15c93bb8 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -13,20 +13,7 @@
 struct cma;
 struct iommu_ops;
 
-/*
- * Values for struct dma_map_ops.flags:
- *
- * DMA_F_PCI_P2PDMA_SUPPORTED: Indicates the dma_map_ops implementation can
- * handle PCI P2PDMA pages in the map_sg/unmap_sg operation.
- * DMA_F_CAN_SKIP_SYNC: DMA sync operations can be skipped if the device is
- * coherent and it's not an SWIOTLB buffer.
- */
-#define DMA_F_PCI_P2PDMA_SUPPORTED     (1 << 0)
-#define DMA_F_CAN_SKIP_SYNC            (1 << 1)
-
 struct dma_map_ops {
-	unsigned int flags;
-
 	void *(*alloc)(struct device *dev, size_t size,
 			dma_addr_t *dma_handle, gfp_t gfp,
 			unsigned long attrs);
diff --git a/include/linux/iommu-dma.h b/include/linux/iommu-dma.h
new file mode 100644
index 000000000000..622232fc9510
--- /dev/null
+++ b/include/linux/iommu-dma.h
@@ -0,0 +1,169 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES. All rights reserved
+ *
+ * DMA operations that map physical memory through IOMMU.
+ */
+#ifndef _LINUX_IOMMU_DMA_H
+#define _LINUX_IOMMU_DMA_H
+
+#include <linux/dma-direction.h>
+
+#ifdef CONFIG_IOMMU_DMA
+dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
+			      unsigned long offset, size_t size,
+			      enum dma_data_direction dir, unsigned long attrs);
+void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
+			  size_t size, enum dma_data_direction dir,
+			  unsigned long attrs);
+int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
+		     enum dma_data_direction dir, unsigned long attrs);
+void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
+			enum dma_data_direction dir, unsigned long attrs);
+void *iommu_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
+		      gfp_t gfp, unsigned long attrs);
+int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+		   void *cpu_addr, dma_addr_t dma_addr,
+		   size_t size, unsigned long attrs);
+int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
+			  void *cpu_addr, dma_addr_t dma_addr, size_t size,
+			  unsigned long attrs);
+unsigned long iommu_dma_get_merge_boundary(struct device *dev);
+size_t iommu_dma_opt_mapping_size(void);
+size_t iommu_dma_max_mapping_size(struct device *dev);
+void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
+		    dma_addr_t handle, unsigned long attrs);
+dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
+				  size_t size, enum dma_data_direction dir,
+				  unsigned long attrs);
+void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
+			      size_t size, enum dma_data_direction dir,
+			      unsigned long attrs);
+struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev, size_t size,
+					       enum dma_data_direction dir,
+					       gfp_t gfp, unsigned long attrs);
+void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
+				  struct sg_table *sgt,
+				  enum dma_data_direction dir);
+void iommu_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
+				   size_t size, enum dma_data_direction dir);
+void iommu_dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle,
+				      size_t size, enum dma_data_direction dir);
+void iommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
+			       int nelems, enum dma_data_direction dir);
+void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
+				  int nelems, enum dma_data_direction dir);
+#else
+static inline dma_addr_t iommu_dma_map_page(struct device *dev,
+					    struct page *page,
+					    unsigned long offset, size_t size,
+					    enum dma_data_direction dir,
+					    unsigned long attrs)
+{
+	return DMA_MAPPING_ERROR;
+}
+static inline void iommu_dma_unmap_page(struct device *dev,
+					dma_addr_t dma_handle, size_t size,
+					enum dma_data_direction dir,
+					unsigned long attrs)
+{
+}
+static inline int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
+				   int nents, enum dma_data_direction dir,
+				   unsigned long attrs)
+{
+	return -EINVAL;
+}
+static inline void iommu_dma_unmap_sg(struct device *dev,
+				      struct scatterlist *sg, int nents,
+				      enum dma_data_direction dir,
+				      unsigned long attrs)
+{
+}
+static inline void *iommu_dma_alloc(struct device *dev, size_t size,
+				    dma_addr_t *handle, gfp_t gfp,
+				    unsigned long attrs)
+{
+	return NULL;
+}
+static inline int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+				 void *cpu_addr, dma_addr_t dma_addr,
+				 size_t size, unsigned long attrs)
+{
+	return -EINVAL;
+}
+static inline int iommu_dma_get_sgtable(struct device *dev,
+					struct sg_table *sgt, void *cpu_addr,
+					dma_addr_t dma_addr, size_t size,
+					unsigned long attrs)
+{
+	return -EINVAL;
+}
+static inline unsigned long iommu_dma_get_merge_boundary(struct device *dev)
+{
+	return 0;
+}
+static inline size_t iommu_dma_opt_mapping_size(void)
+{
+	return 0;
+}
+static inline size_t iommu_dma_max_mapping_size(struct device *dev)
+{
+	return 0;
+}
+static inline void iommu_dma_free(struct device *dev, size_t size,
+				  void *cpu_addr, dma_addr_t handle,
+				  unsigned long attrs)
+{
+}
+static inline dma_addr_t iommu_dma_map_resource(struct device *dev,
+						phys_addr_t phys, size_t size,
+						enum dma_data_direction dir,
+						unsigned long attrs)
+{
+	return DMA_MAPPING_ERROR;
+}
+static inline void iommu_dma_unmap_resource(struct device *dev,
+					    dma_addr_t handle, size_t size,
+					    enum dma_data_direction dir,
+					    unsigned long attrs)
+{
+}
+static inline struct sg_table *
+iommu_dma_alloc_noncontiguous(struct device *dev, size_t size,
+			      enum dma_data_direction dir, gfp_t gfp,
+			      unsigned long attrs)
+{
+	return NULL;
+}
+static inline void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
+						struct sg_table *sgt,
+						enum dma_data_direction dir)
+{
+}
+static inline void iommu_dma_sync_single_for_cpu(struct device *dev,
+						 dma_addr_t dma_handle,
+						 size_t size,
+						 enum dma_data_direction dir)
+{
+}
+static inline void iommu_dma_sync_single_for_device(struct device *dev,
+						    dma_addr_t dma_handle,
+						    size_t size,
+						    enum dma_data_direction dir)
+{
+}
+static inline void iommu_dma_sync_sg_for_cpu(struct device *dev,
+					     struct scatterlist *sgl,
+					     int nelems,
+					     enum dma_data_direction dir)
+{
+}
+static inline void iommu_dma_sync_sg_for_device(struct device *dev,
+						struct scatterlist *sgl,
+						int nelems,
+						enum dma_data_direction dir)
+{
+}
+#endif /* CONFIG_IOMMU_DMA */
+#endif /* _LINUX_IOMMU_DMA_H */
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 6832fd6f0796..feaa69c35f79 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -8,6 +8,7 @@
 #include <linux/memblock.h> /* for max_pfn */
 #include <linux/acpi.h>
 #include <linux/dma-map-ops.h>
+#include <linux/iommu-dma.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
 #include <linux/kmsan.h>
@@ -113,12 +114,24 @@ void *dmam_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
 }
 EXPORT_SYMBOL(dmam_alloc_attrs);
 
+static inline bool dma_is_default_iommu(struct device *dev)
+{
+#ifdef CONFIG_IOMMU_DMA
+	return dev->dma_iommu;
+#else
+	return false;
+#endif
+}
+
 static bool dma_go_direct(struct device *dev, dma_addr_t mask,
 		const struct dma_map_ops *ops)
 {
-	if (likely(!ops))
+	WARN_ON_ONCE(ops && dma_is_default_iommu(dev));
+	if (likely(!ops) && !dma_is_default_iommu(dev))
 		return true;
+
 #ifdef CONFIG_DMA_OPS_BYPASS
+	WARN_ON_ONCE(dev->dma_ops_bypass && dma_is_default_iommu(dev));
 	if (dev->dma_ops_bypass)
 		return min_not_zero(mask, dev->bus_dma_limit) >=
 			    dma_direct_get_required_mask(dev);
@@ -159,6 +172,8 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 	if (dma_map_direct(dev, ops) ||
 	    arch_dma_map_page_direct(dev, page_to_phys(page) + offset + size))
 		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
+	else if (dma_is_default_iommu(dev))
+		addr = iommu_dma_map_page(dev, page, offset, size, dir, attrs);
 	else
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
 	kmsan_handle_dma(page, offset, size, dir);
@@ -177,6 +192,8 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 	if (dma_map_direct(dev, ops) ||
 	    arch_dma_unmap_page_direct(dev, addr + size))
 		dma_direct_unmap_page(dev, addr, size, dir, attrs);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_unmap_page(dev, addr, size, dir, attrs);
 	else
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	debug_dma_unmap_page(dev, addr, size, dir);
@@ -197,6 +214,8 @@ static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 	if (dma_map_direct(dev, ops) ||
 	    arch_dma_map_sg_direct(dev, sg, nents))
 		ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
+	else if (dma_is_default_iommu(dev))
+		ents = iommu_dma_map_sg(dev, sg, nents, dir, attrs);
 	else
 		ents = ops->map_sg(dev, sg, nents, dir, attrs);
 
@@ -291,6 +310,8 @@ void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
 	if (dma_map_direct(dev, ops) ||
 	    arch_dma_unmap_sg_direct(dev, sg, nents))
 		dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_unmap_sg(dev, sg, nents, dir, attrs);
 	else
 		ops->unmap_sg(dev, sg, nents, dir, attrs);
 }
@@ -309,6 +330,8 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
 
 	if (dma_map_direct(dev, ops))
 		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
+	else if (dma_is_default_iommu(dev))
+		addr = iommu_dma_map_resource(dev, phys_addr, size, dir, attrs);
 	else if (ops->map_resource)
 		addr = ops->map_resource(dev, phys_addr, size, dir, attrs);
 
@@ -323,8 +346,12 @@ void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	BUG_ON(!valid_dma_direction(dir));
-	if (!dma_map_direct(dev, ops) && ops->unmap_resource)
-		ops->unmap_resource(dev, addr, size, dir, attrs);
+	if (!dma_map_direct(dev, ops)) {
+		if (dma_is_default_iommu(dev))
+			iommu_dma_unmap_resource(dev, addr, size, dir, attrs);
+		else if (ops->unmap_resource)
+			ops->unmap_resource(dev, addr, size, dir, attrs);
+	}
 	debug_dma_unmap_resource(dev, addr, size, dir);
 }
 EXPORT_SYMBOL(dma_unmap_resource);
@@ -338,6 +365,8 @@ void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
 	BUG_ON(!valid_dma_direction(dir));
 	if (dma_map_direct(dev, ops))
 		dma_direct_sync_single_for_cpu(dev, addr, size, dir);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_sync_single_for_cpu(dev, addr, size, dir);
 	else if (ops->sync_single_for_cpu)
 		ops->sync_single_for_cpu(dev, addr, size, dir);
 	debug_dma_sync_single_for_cpu(dev, addr, size, dir);
@@ -352,6 +381,8 @@ void __dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
 	BUG_ON(!valid_dma_direction(dir));
 	if (dma_map_direct(dev, ops))
 		dma_direct_sync_single_for_device(dev, addr, size, dir);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_sync_single_for_device(dev, addr, size, dir);
 	else if (ops->sync_single_for_device)
 		ops->sync_single_for_device(dev, addr, size, dir);
 	debug_dma_sync_single_for_device(dev, addr, size, dir);
@@ -366,6 +397,8 @@ void __dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
 	BUG_ON(!valid_dma_direction(dir));
 	if (dma_map_direct(dev, ops))
 		dma_direct_sync_sg_for_cpu(dev, sg, nelems, dir);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
 	else if (ops->sync_sg_for_cpu)
 		ops->sync_sg_for_cpu(dev, sg, nelems, dir);
 	debug_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
@@ -380,6 +413,8 @@ void __dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
 	BUG_ON(!valid_dma_direction(dir));
 	if (dma_map_direct(dev, ops))
 		dma_direct_sync_sg_for_device(dev, sg, nelems, dir);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_sync_sg_for_device(dev, sg, nelems, dir);
 	else if (ops->sync_sg_for_device)
 		ops->sync_sg_for_device(dev, sg, nelems, dir);
 	debug_dma_sync_sg_for_device(dev, sg, nelems, dir);
@@ -405,7 +440,7 @@ static void dma_setup_need_sync(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (dma_map_direct(dev, ops) || (ops->flags & DMA_F_CAN_SKIP_SYNC))
+	if (dma_map_direct(dev, ops) || dma_is_default_iommu(dev))
 		/*
 		 * dma_skip_sync will be reset to %false on first SWIOTLB buffer
 		 * mapping, if any. During the device initialization, it's
@@ -446,6 +481,9 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
 	if (dma_alloc_direct(dev, ops))
 		return dma_direct_get_sgtable(dev, sgt, cpu_addr, dma_addr,
 				size, attrs);
+	if (dma_is_default_iommu(dev))
+		return iommu_dma_get_sgtable(dev, sgt, cpu_addr, dma_addr,
+				size, attrs);
 	if (!ops->get_sgtable)
 		return -ENXIO;
 	return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size, attrs);
@@ -482,6 +520,8 @@ bool dma_can_mmap(struct device *dev)
 
 	if (dma_alloc_direct(dev, ops))
 		return dma_direct_can_mmap(dev);
+	if (dma_is_default_iommu(dev))
+		return true;
 	return ops->mmap != NULL;
 }
 EXPORT_SYMBOL_GPL(dma_can_mmap);
@@ -508,6 +548,9 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
 	if (dma_alloc_direct(dev, ops))
 		return dma_direct_mmap(dev, vma, cpu_addr, dma_addr, size,
 				attrs);
+	if (dma_is_default_iommu(dev))
+		return iommu_dma_mmap(dev, vma, cpu_addr, dma_addr, size,
+				      attrs);
 	if (!ops->mmap)
 		return -ENXIO;
 	return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
@@ -559,6 +602,8 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
 
 	if (dma_alloc_direct(dev, ops))
 		cpu_addr = dma_direct_alloc(dev, size, dma_handle, flag, attrs);
+	else if (dma_is_default_iommu(dev))
+		cpu_addr = iommu_dma_alloc(dev, size, dma_handle, flag, attrs);
 	else if (ops->alloc)
 		cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
 	else
@@ -591,6 +636,8 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 	debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
 	if (dma_alloc_direct(dev, ops))
 		dma_direct_free(dev, size, cpu_addr, dma_handle, attrs);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_free(dev, size, cpu_addr, dma_handle, attrs);
 	else if (ops->free)
 		ops->free(dev, size, cpu_addr, dma_handle, attrs);
 }
@@ -611,6 +658,8 @@ static struct page *__dma_alloc_pages(struct device *dev, size_t size,
 	size = PAGE_ALIGN(size);
 	if (dma_alloc_direct(dev, ops))
 		return dma_direct_alloc_pages(dev, size, dma_handle, dir, gfp);
+	if (dma_is_default_iommu(dev))
+		return dma_common_alloc_pages(dev, size, dma_handle, dir, gfp);
 	if (!ops->alloc_pages_op)
 		return NULL;
 	return ops->alloc_pages_op(dev, size, dma_handle, dir, gfp);
@@ -635,6 +684,8 @@ static void __dma_free_pages(struct device *dev, size_t size, struct page *page,
 	size = PAGE_ALIGN(size);
 	if (dma_alloc_direct(dev, ops))
 		dma_direct_free_pages(dev, size, page, dma_handle, dir);
+	else if (dma_is_default_iommu(dev))
+		dma_common_free_pages(dev, size, page, dma_handle, dir);
 	else if (ops->free_pages)
 		ops->free_pages(dev, size, page, dma_handle, dir);
 }
@@ -697,6 +748,8 @@ struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size,
 
 	if (ops && ops->alloc_noncontiguous)
 		sgt = ops->alloc_noncontiguous(dev, size, dir, gfp, attrs);
+	else if (dma_is_default_iommu(dev))
+		sgt = iommu_dma_alloc_noncontiguous(dev, size, dir, gfp, attrs);
 	else
 		sgt = alloc_single_sgt(dev, size, dir, gfp);
 
@@ -725,6 +778,8 @@ void dma_free_noncontiguous(struct device *dev, size_t size,
 	debug_dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, dir);
 	if (ops && ops->free_noncontiguous)
 		ops->free_noncontiguous(dev, size, sgt, dir);
+	else if (dma_is_default_iommu(dev))
+		iommu_dma_free_noncontiguous(dev, size, sgt, dir);
 	else
 		free_single_sgt(dev, size, sgt, dir);
 }
@@ -787,17 +842,14 @@ bool dma_pci_p2pdma_supported(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	/* if ops is not set, dma direct will be used which supports P2PDMA */
-	if (!ops)
-		return true;
-
 	/*
 	 * Note: dma_ops_bypass is not checked here because P2PDMA should
 	 * not be used with dma mapping ops that do not have support even
 	 * if the specific device is bypassing them.
 	 */
 
-	return ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED;
+	/* if ops is not set, dma direct and default IOMMU support P2PDMA */
+	return (!ops || dma_is_default_iommu(dev));
 }
 EXPORT_SYMBOL_GPL(dma_pci_p2pdma_supported);
 
@@ -865,6 +917,8 @@ size_t dma_max_mapping_size(struct device *dev)
 
 	if (dma_map_direct(dev, ops))
 		size = dma_direct_max_mapping_size(dev);
+	else if (dma_is_default_iommu(dev))
+		size = iommu_dma_max_mapping_size(dev);
 	else if (ops && ops->max_mapping_size)
 		size = ops->max_mapping_size(dev);
 
@@ -877,9 +931,10 @@ size_t dma_opt_mapping_size(struct device *dev)
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 	size_t size = SIZE_MAX;
 
-	if (ops && ops->opt_mapping_size)
+	if (dma_is_default_iommu(dev))
+		size = iommu_dma_opt_mapping_size();
+	else if (ops && ops->opt_mapping_size)
 		size = ops->opt_mapping_size();
-
 	return min(dma_max_mapping_size(dev), size);
 }
 EXPORT_SYMBOL_GPL(dma_opt_mapping_size);
@@ -888,7 +943,12 @@ unsigned long dma_get_merge_boundary(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
-	if (!ops || !ops->get_merge_boundary)
+	if (!ops)
+		return 0;	/* can't merge */
+	if (dma_is_default_iommu(dev))
+		return iommu_dma_get_merge_boundary(dev);
+
+	if (!ops->get_merge_boundary)
 		return 0;	/* can't merge */
 
 	return ops->get_merge_boundary(dev);
-- 
2.45.2

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Christoph Hellwig]

On Wed, Jul 17, 2024 at 03:37:11PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> Most of the arch DMA ops (which often, but not  always, involve
> some sort of IOMMU) are using the same DMA operations. These DMA
> operations are default ones implemented in drivers/iomem/dma-iommu.c.

I'm not sure I agree with the exact wording.  There's tons of arch DMA
ops not in any way tied to dma-iommu (or the iommu subsystem, but not
dma-iommu like the arm32 ones), but for all modern platforms dma-iommu
is what actually matters.

> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> Signed-off-by: Leon Romanovsky <leon@kernel.org>

A double-signoff for the same person is a bit weird, isn't it?

>  	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> @@ -1756,10 +1733,10 @@ void iommu_setup_dma_ops(struct device *dev)
>  	if (iommu_is_dma_domain(domain)) {
>  		if (iommu_dma_init_domain(domain, dev))
>  			goto out_err;
> +		dev->dma_iommu = true;
> +	} else if (dev->dma_iommu) {
>  		/* Clean up if we've switched *from* a DMA domain */
> +		dev->dma_iommu = false;
>  	}

Strictly speaking we can no remove the if part of the else if above.
Or reword this a bit to:

	dev->dma_iommu = iommu_is_dma_domain(domain);
	if (dev->dma_iommu && iommu_dma_init_domain(domain, dev))
		goto out_err;

> diff --git a/include/linux/device.h b/include/linux/device.h
> index ace039151cb8..7fa1e40b617a 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -822,6 +822,9 @@ struct device {
>  #ifdef CONFIG_DMA_NEED_SYNC
>  	bool			dma_skip_sync:1;
>  #endif
> +#ifdef CONFIG_IOMMU_DMA
> +	bool			dma_iommu : 1;
> +#endif

The kerneldoc above should be updated to describe this field.
Please also add the maintainers of this file to the next round.

> +static inline bool dma_is_default_iommu(struct device *dev)
> +{
> +#ifdef CONFIG_IOMMU_DMA
> +	return dev->dma_iommu;
> +#else
> +	return false;
> +#endif
> +}

The normal style would be to move the ifdefs outside the helper
function.  Also maybe name this use_dma_iommu?

>  static bool dma_go_direct(struct device *dev, dma_addr_t mask,
>  		const struct dma_map_ops *ops)
>  {
> +	WARN_ON_ONCE(ops && dma_is_default_iommu(dev));

I'd prefer to keep this out of the fast path and only do it in
say dma_set_mask.  And fail the call while we're at it.

> +	if (likely(!ops) && !dma_is_default_iommu(dev))

The likely should cover both conditions.

>  		return true;
> +
>  #ifdef CONFIG_DMA_OPS_BYPASS
> +	WARN_ON_ONCE(dev->dma_ops_bypass && dma_is_default_iommu(dev));
>  	if (dev->dma_ops_bypass)

Let's skip this and think about it if we ever use the bypass for
something that is not powerpc with it's own dma ops.

> @@ -323,8 +346,12 @@ void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
>  
>  	BUG_ON(!valid_dma_direction(dir));
> -	if (!dma_map_direct(dev, ops) && ops->unmap_resource)
> -		ops->unmap_resource(dev, addr, size, dir, attrs);
> +	if (!dma_map_direct(dev, ops)) {
> +		if (dma_is_default_iommu(dev))
> +			iommu_dma_unmap_resource(dev, addr, size, dir, attrs);
> +		else if (ops->unmap_resource)
> +			ops->unmap_resource(dev, addr, size, dir, attrs);
> +	}

I'd prefer to order this as:

	if (dma_map_direct(dev, ops))
		; /* nothing to do: uncached and no swiotlb */
	else if (use_dma_iommu(dev))
		iommu_dma_unmap_resource(dev, addr, size, dir, attrs);
	else if (ops->unmap_resource)
		ops->unmap_resource(dev, addr, size, dir, attrs);

> +	return (!ops || dma_is_default_iommu(dev));

dma_is_default_iommu implies !ops, so the second condition is
redundant.

>  EXPORT_SYMBOL_GPL(dma_opt_mapping_size);
> @@ -888,7 +943,12 @@ unsigned long dma_get_merge_boundary(struct device *dev)
>  {
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
>  
> +	if (!ops)
> +		return 0;	/* can't merge */
> +	if (dma_is_default_iommu(dev))
> +		return iommu_dma_get_merge_boundary(dev);

The second check needs to move up here.

Re: [PATCH v2 1/2] dma: call unconditionally to unmap_page and unmap_sg callbacks

[Christoph Hellwig]

On Wed, Jul 17, 2024 at 03:37:10PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> Almost all users of ->map_page()/map_sg() callbacks implement
> ->unmap_page()/unmap_sg() callbacks too. One user which doesn't do it,
> is dummy DMA ops interface, and the use of this interface is to fail
> the operation and in such case, there won't be any call to
> ->unmap_page()/unmap_sg().
> 
> This patch removes the existence checks of ->unmap_page()/unmap_sg()
> and calls to it directly to create symmetrical interface to
> ->map_page()/map_sg().

I don't think you even need this any more, do you?

Re: [PATCH v2 1/2] dma: call unconditionally to unmap_page and unmap_sg callbacks

[Leon Romanovsky]

On Thu, Jul 18, 2024 at 05:49:10AM +0200, Christoph Hellwig wrote:
> On Wed, Jul 17, 2024 at 03:37:10PM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@nvidia.com>
> > 
> > Almost all users of ->map_page()/map_sg() callbacks implement
> > ->unmap_page()/unmap_sg() callbacks too. One user which doesn't do it,
> > is dummy DMA ops interface, and the use of this interface is to fail
> > the operation and in such case, there won't be any call to
> > ->unmap_page()/unmap_sg().
> > 
> > This patch removes the existence checks of ->unmap_page()/unmap_sg()
> > and calls to it directly to create symmetrical interface to
> > ->map_page()/map_sg().
> 
> I don't think you even need this any more, do you?

Strictly saying, I don't need it, but it is still worth to have this
patch. It removes unnecessary "if" check and makes sure that all callers
of map_XXX() will provide unmap_XXX() too.

Without this patch, the code will look like:

  313         else if (dma_is_default_iommu(dev))
  314                 iommu_dma_unmap_sg(dev, sg, nents, dir, attrs);
  315         else if (ops->unmap_sg)
  316                 ops->unmap_sg(dev, sg, nents, dir, attrs);

With this patch:

  313         else if (dma_is_default_iommu(dev))
  314                 iommu_dma_unmap_sg(dev, sg, nents, dir, attrs);
  315         else
  316                 ops->unmap_sg(dev, sg, nents, dir, attrs);

Thanks

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Leon Romanovsky]

On Thu, Jul 18, 2024 at 05:48:54AM +0200, Christoph Hellwig wrote:
> On Wed, Jul 17, 2024 at 03:37:11PM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@nvidia.com>
> > 
> > Most of the arch DMA ops (which often, but not  always, involve
> > some sort of IOMMU) are using the same DMA operations. These DMA
> > operations are default ones implemented in drivers/iomem/dma-iommu.c.
> 
> I'm not sure I agree with the exact wording.  There's tons of arch DMA
> ops not in any way tied to dma-iommu (or the iommu subsystem, but not
> dma-iommu like the arm32 ones), but for all modern platforms dma-iommu
> is what actually matters.

I can change to any other wording, whatever you think is better.

> 
> > Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> > Signed-off-by: Leon Romanovsky <leon@kernel.org>
> 
> A double-signoff for the same person is a bit weird, isn't it?

Sorry about that, it is a mistake in my tooling.

> 
> >  	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> > @@ -1756,10 +1733,10 @@ void iommu_setup_dma_ops(struct device *dev)
> >  	if (iommu_is_dma_domain(domain)) {
> >  		if (iommu_dma_init_domain(domain, dev))
> >  			goto out_err;
> > +		dev->dma_iommu = true;
> > +	} else if (dev->dma_iommu) {
> >  		/* Clean up if we've switched *from* a DMA domain */
> > +		dev->dma_iommu = false;
> >  	}
> 
> Strictly speaking we can no remove the if part of the else if above.
> Or reword this a bit to:
> 
> 	dev->dma_iommu = iommu_is_dma_domain(domain);
> 	if (dev->dma_iommu && iommu_dma_init_domain(domain, dev))
> 		goto out_err;

I'll change

> 
> > diff --git a/include/linux/device.h b/include/linux/device.h
> > index ace039151cb8..7fa1e40b617a 100644
> > --- a/include/linux/device.h
> > +++ b/include/linux/device.h
> > @@ -822,6 +822,9 @@ struct device {
> >  #ifdef CONFIG_DMA_NEED_SYNC
> >  	bool			dma_skip_sync:1;
> >  #endif
> > +#ifdef CONFIG_IOMMU_DMA
> > +	bool			dma_iommu : 1;
> > +#endif
> 
> The kerneldoc above should be updated to describe this field.

Will do

> Please also add the maintainers of this file to the next round.

I added them, there is no special maintainer for include/linux/device.h file:
➜  kernel git:(dma-static-calls-v2) ✗ ./scripts/get_maintainer.pl --git-min-percent 100 /tmp/e/v2-0002-dma-add-IOMMU-static-calls-with-clear-default-ops.patch
Joerg Roedel <joro@8bytes.org> (maintainer:IOMMU SUBSYSTEM)
Will Deacon <will@kernel.org> (maintainer:IOMMU SUBSYSTEM)
Robin Murphy <robin.murphy@arm.com> (reviewer:IOMMU SUBSYSTEM)
Christoph Hellwig <hch@lst.de> (supporter:DMA MAPPING HELPERS)
Marek Szyprowski <m.szyprowski@samsung.com> (supporter:DMA MAPPING HELPERS)
linux-kernel@vger.kernel.org (open list)
iommu@lists.linux.dev (open list:IOMMU SUBSYSTEM)

Whom should I add?

> 
> > +static inline bool dma_is_default_iommu(struct device *dev)
> > +{
> > +#ifdef CONFIG_IOMMU_DMA
> > +	return dev->dma_iommu;
> > +#else
> > +	return false;
> > +#endif
> > +}
> 
> The normal style would be to move the ifdefs outside the helper
> function.

I think you are talking about the style of functions declarations in
header files. This function is inside c-file and it is much easier
to write it this way. 


> Also maybe name this use_dma_iommu?

Sure, I'll change it.

> 
> >  static bool dma_go_direct(struct device *dev, dma_addr_t mask,
> >  		const struct dma_map_ops *ops)
> >  {
> > +	WARN_ON_ONCE(ops && dma_is_default_iommu(dev));
> 
> I'd prefer to keep this out of the fast path and only do it in
> say dma_set_mask.  And fail the call while we're at it.

I will add it to dma_supported().

> 
> > +	if (likely(!ops) && !dma_is_default_iommu(dev))
> 
> The likely should cover both conditions.

Sure

> 
> >  		return true;
> > +
> >  #ifdef CONFIG_DMA_OPS_BYPASS
> > +	WARN_ON_ONCE(dev->dma_ops_bypass && dma_is_default_iommu(dev));
> >  	if (dev->dma_ops_bypass)
> 
> Let's skip this and think about it if we ever use the bypass for
> something that is not powerpc with it's own dma ops.

I wanted to catch misconfigurations, but I can remove it. Is this what
you are suggesting?

  126 static bool dma_go_direct(struct device *dev, dma_addr_t mask, 
  127                 const struct dma_map_ops *ops)                
  128 {                                                            
  129         if (likely(!ops && !dma_is_default_iommu(dev)))     
  130                 return true;                               
  131                                                           
  132         if (dma_is_default_iommu(dev))    
  133                 return false;
  134                             
  135 #ifdef CONFIG_DMA_OPS_BYPASS 
  136         if (dev->dma_ops_bypass)
  137                 return min_not_zero(mask, dev->bus_dma_limit) >= 
  138                             dma_direct_get_required_mask(dev);  
  139 #endif                                                         
  140         return false;                                         
  141 }         

> 
> > @@ -323,8 +346,12 @@ void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
> >  	const struct dma_map_ops *ops = get_dma_ops(dev);
> >  
> >  	BUG_ON(!valid_dma_direction(dir));
> > -	if (!dma_map_direct(dev, ops) && ops->unmap_resource)
> > -		ops->unmap_resource(dev, addr, size, dir, attrs);
> > +	if (!dma_map_direct(dev, ops)) {
> > +		if (dma_is_default_iommu(dev))
> > +			iommu_dma_unmap_resource(dev, addr, size, dir, attrs);
> > +		else if (ops->unmap_resource)
> > +			ops->unmap_resource(dev, addr, size, dir, attrs);
> > +	}
> 
> I'd prefer to order this as:
> 
> 	if (dma_map_direct(dev, ops))
> 		; /* nothing to do: uncached and no swiotlb */
> 	else if (use_dma_iommu(dev))
> 		iommu_dma_unmap_resource(dev, addr, size, dir, attrs);
> 	else if (ops->unmap_resource)
> 		ops->unmap_resource(dev, addr, size, dir, attrs);

I will change.

> 
> > +	return (!ops || dma_is_default_iommu(dev));
> 
> dma_is_default_iommu implies !ops, so the second condition is
> redundant.

Right

> 
> >  EXPORT_SYMBOL_GPL(dma_opt_mapping_size);
> > @@ -888,7 +943,12 @@ unsigned long dma_get_merge_boundary(struct device *dev)
> >  {
> >  	const struct dma_map_ops *ops = get_dma_ops(dev);
> >  
> > +	if (!ops)
> > +		return 0;	/* can't merge */
> > +	if (dma_is_default_iommu(dev))
> > +		return iommu_dma_get_merge_boundary(dev);
> 
> The second check needs to move up here.

Right, will fix.

I'll send v3 after weekend.

Thanks

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Christoph Hellwig]

On Thu, Jul 18, 2024 at 10:04:06AM +0300, Leon Romanovsky wrote:
> Whom should I add?

Greg as the device model maintainer.

> > The normal style would be to move the ifdefs outside the helper
> > function.
> 
> I think you are talking about the style of functions declarations in
> header files. This function is inside c-file and it is much easier
> to write it this way. 

But also much harder to read, which will happen much more often.

> > >  #ifdef CONFIG_DMA_OPS_BYPASS
> > > +	WARN_ON_ONCE(dev->dma_ops_bypass && dma_is_default_iommu(dev));
> > >  	if (dev->dma_ops_bypass)
> > 
> > Let's skip this and think about it if we ever use the bypass for
> > something that is not powerpc with it's own dma ops.
> 
> I wanted to catch misconfigurations, but I can remove it. Is this what
> you are suggesting?
> 
>   126 static bool dma_go_direct(struct device *dev, dma_addr_t mask, 
>   127                 const struct dma_map_ops *ops)                
>   128 {                                                            
>   129         if (likely(!ops && !dma_is_default_iommu(dev)))     
>   130                 return true;                               
>   131                                                           
>   132         if (dma_is_default_iommu(dev))    
>   133                 return false;

I'd go for:

		if (use_dma_iommu(dev))
			return false;
		if (likely(!ops))
			return true;
		...

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Leon Romanovsky]

On Thu, Jul 18, 2024 at 02:30:38PM +0200, Christoph Hellwig wrote:
> On Thu, Jul 18, 2024 at 10:04:06AM +0300, Leon Romanovsky wrote:
> > Whom should I add?
> 
> Greg as the device model maintainer.

No problem, I will add him to the next version.

> 
> > > The normal style would be to move the ifdefs outside the helper
> > > function.
> > 
> > I think you are talking about the style of functions declarations in
> > header files. This function is inside c-file and it is much easier
> > to write it this way. 
> 
> But also much harder to read, which will happen much more often.

I'll change.

> 
> > > >  #ifdef CONFIG_DMA_OPS_BYPASS
> > > > +	WARN_ON_ONCE(dev->dma_ops_bypass && dma_is_default_iommu(dev));
> > > >  	if (dev->dma_ops_bypass)
> > > 
> > > Let's skip this and think about it if we ever use the bypass for
> > > something that is not powerpc with it's own dma ops.
> > 
> > I wanted to catch misconfigurations, but I can remove it. Is this what
> > you are suggesting?
> > 
> >   126 static bool dma_go_direct(struct device *dev, dma_addr_t mask, 
> >   127                 const struct dma_map_ops *ops)                
> >   128 {                                                            
> >   129         if (likely(!ops && !dma_is_default_iommu(dev)))     
> >   130                 return true;                               
> >   131                                                           
> >   132         if (dma_is_default_iommu(dev))    
> >   133                 return false;
> 
> I'd go for:
> 
> 		if (use_dma_iommu(dev))
> 			return false;
> 		if (likely(!ops))
> 			return true;
> 		...
> 

I will change.

Thanks

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Mostafa Saleh]

Hi Leon,

On Wed, Jul 17, 2024 at 03:37:11PM +0300, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
> 
> Most of the arch DMA ops (which often, but not  always, involve
> some sort of IOMMU) are using the same DMA operations. These DMA
> operations are default ones implemented in drivers/iomem/dma-iommu.c.
> 
> So let's make sure to call them directly without need to perform function
> pointers dereference.

Just out of curiosity, is there any observed improvement from that?
As from my experience the DMA-IOMMU path is quite dense so it won't
be senstive to such micro-optimizations.

Thanks,
Mostafa

> 
> During system initialization, the arch can set its own DMA and in such case,
> the default DMA operations will be overridden.
> 
> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
> Signed-off-by: Leon Romanovsky <leon@kernel.org>
> ---
>  MAINTAINERS                 |   1 +
>  drivers/iommu/Kconfig       |   1 -
>  drivers/iommu/dma-iommu.c   | 117 ++++++++++---------------
>  include/linux/device.h      |   3 +
>  include/linux/dma-map-ops.h |  13 ---
>  include/linux/iommu-dma.h   | 169 ++++++++++++++++++++++++++++++++++++
>  kernel/dma/mapping.c        |  84 +++++++++++++++---
>  7 files changed, 292 insertions(+), 96 deletions(-)
>  create mode 100644 include/linux/iommu-dma.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 958e935449e5..ce06c4df7e05 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -11525,6 +11525,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/iommu/linux.git
>  F:	Documentation/devicetree/bindings/iommu/
>  F:	Documentation/userspace-api/iommu.rst
>  F:	drivers/iommu/
> +F:	include/linux/iommu-dma.h
>  F:	include/linux/iommu.h
>  F:	include/linux/iova.h
>  F:	include/linux/of_iommu.h
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index c04584be3089..e0dd30c1b08a 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -151,7 +151,6 @@ config OF_IOMMU
>  # IOMMU-agnostic DMA-mapping layer
>  config IOMMU_DMA
>  	def_bool ARM64 || X86 || S390
> -	select DMA_OPS
>  	select IOMMU_API
>  	select IOMMU_IOVA
>  	select IRQ_MSI_IOMMU
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 43520e7275cc..174b84f9cd92 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -17,6 +17,7 @@
>  #include <linux/gfp.h>
>  #include <linux/huge_mm.h>
>  #include <linux/iommu.h>
> +#include <linux/iommu-dma.h>
>  #include <linux/iova.h>
>  #include <linux/irq.h>
>  #include <linux/list_sort.h>
> @@ -1039,9 +1040,9 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
>  	return NULL;
>  }
>  
> -static struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev,
> -		size_t size, enum dma_data_direction dir, gfp_t gfp,
> -		unsigned long attrs)
> +struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev, size_t size,
> +					       enum dma_data_direction dir,
> +					       gfp_t gfp, unsigned long attrs)
>  {
>  	struct dma_sgt_handle *sh;
>  
> @@ -1058,8 +1059,9 @@ static struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev,
>  	return &sh->sgt;
>  }
>  
> -static void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
> -		struct sg_table *sgt, enum dma_data_direction dir)
> +void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
> +				  struct sg_table *sgt,
> +				  enum dma_data_direction dir)
>  {
>  	struct dma_sgt_handle *sh = sgt_handle(sgt);
>  
> @@ -1069,8 +1071,8 @@ static void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
>  	kfree(sh);
>  }
>  
> -static void iommu_dma_sync_single_for_cpu(struct device *dev,
> -		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
> +void iommu_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
> +				   size_t size, enum dma_data_direction dir)
>  {
>  	phys_addr_t phys;
>  
> @@ -1085,8 +1087,8 @@ static void iommu_dma_sync_single_for_cpu(struct device *dev,
>  		swiotlb_sync_single_for_cpu(dev, phys, size, dir);
>  }
>  
> -static void iommu_dma_sync_single_for_device(struct device *dev,
> -		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
> +void iommu_dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle,
> +				      size_t size, enum dma_data_direction dir)
>  {
>  	phys_addr_t phys;
>  
> @@ -1101,9 +1103,8 @@ static void iommu_dma_sync_single_for_device(struct device *dev,
>  		arch_sync_dma_for_device(phys, size, dir);
>  }
>  
> -static void iommu_dma_sync_sg_for_cpu(struct device *dev,
> -		struct scatterlist *sgl, int nelems,
> -		enum dma_data_direction dir)
> +void iommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
> +			       int nelems, enum dma_data_direction dir)
>  {
>  	struct scatterlist *sg;
>  	int i;
> @@ -1117,9 +1118,8 @@ static void iommu_dma_sync_sg_for_cpu(struct device *dev,
>  			arch_sync_dma_for_cpu(sg_phys(sg), sg->length, dir);
>  }
>  
> -static void iommu_dma_sync_sg_for_device(struct device *dev,
> -		struct scatterlist *sgl, int nelems,
> -		enum dma_data_direction dir)
> +void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
> +				  int nelems, enum dma_data_direction dir)
>  {
>  	struct scatterlist *sg;
>  	int i;
> @@ -1134,9 +1134,9 @@ static void iommu_dma_sync_sg_for_device(struct device *dev,
>  			arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
>  }
>  
> -static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> -		unsigned long offset, size_t size, enum dma_data_direction dir,
> -		unsigned long attrs)
> +dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> +			      unsigned long offset, size_t size,
> +			      enum dma_data_direction dir, unsigned long attrs)
>  {
>  	phys_addr_t phys = page_to_phys(page) + offset;
>  	bool coherent = dev_is_dma_coherent(dev);
> @@ -1194,8 +1194,9 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
>  	return iova;
>  }
>  
> -static void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
> -		size_t size, enum dma_data_direction dir, unsigned long attrs)
> +void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
> +			  size_t size, enum dma_data_direction dir,
> +			  unsigned long attrs)
>  {
>  	struct iommu_domain *domain = iommu_get_dma_domain(dev);
>  	phys_addr_t phys;
> @@ -1348,8 +1349,8 @@ static int iommu_dma_map_sg_swiotlb(struct device *dev, struct scatterlist *sg,
>   * impedance-matching, to be able to hand off a suitably-aligned list,
>   * but still preserve the original offsets and sizes for the caller.
>   */
> -static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
> -		int nents, enum dma_data_direction dir, unsigned long attrs)
> +int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
> +		     enum dma_data_direction dir, unsigned long attrs)
>  {
>  	struct iommu_domain *domain = iommu_get_dma_domain(dev);
>  	struct iommu_dma_cookie *cookie = domain->iova_cookie;
> @@ -1468,8 +1469,8 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
>  	return ret;
>  }
>  
> -static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
> -		int nents, enum dma_data_direction dir, unsigned long attrs)
> +void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
> +			enum dma_data_direction dir, unsigned long attrs)
>  {
>  	dma_addr_t end = 0, start;
>  	struct scatterlist *tmp;
> @@ -1518,16 +1519,18 @@ static void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg,
>  		__iommu_dma_unmap(dev, start, end - start);
>  }
>  
> -static dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
> -		size_t size, enum dma_data_direction dir, unsigned long attrs)
> +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
> +				  size_t size, enum dma_data_direction dir,
> +				  unsigned long attrs)
>  {
>  	return __iommu_dma_map(dev, phys, size,
>  			dma_info_to_prot(dir, false, attrs) | IOMMU_MMIO,
>  			dma_get_mask(dev));
>  }
>  
> -static void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
> -		size_t size, enum dma_data_direction dir, unsigned long attrs)
> +void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
> +			      size_t size, enum dma_data_direction dir,
> +			      unsigned long attrs)
>  {
>  	__iommu_dma_unmap(dev, handle, size);
>  }
> @@ -1563,8 +1566,8 @@ static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
>  		dma_free_contiguous(dev, page, alloc_size);
>  }
>  
> -static void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
> -		dma_addr_t handle, unsigned long attrs)
> +void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
> +		    dma_addr_t handle, unsigned long attrs)
>  {
>  	__iommu_dma_unmap(dev, handle, size);
>  	__iommu_dma_free(dev, size, cpu_addr);
> @@ -1607,8 +1610,8 @@ static void *iommu_dma_alloc_pages(struct device *dev, size_t size,
>  	return NULL;
>  }
>  
> -static void *iommu_dma_alloc(struct device *dev, size_t size,
> -		dma_addr_t *handle, gfp_t gfp, unsigned long attrs)
> +void *iommu_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> +		      gfp_t gfp, unsigned long attrs)
>  {
>  	bool coherent = dev_is_dma_coherent(dev);
>  	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
> @@ -1642,9 +1645,9 @@ static void *iommu_dma_alloc(struct device *dev, size_t size,
>  	return cpu_addr;
>  }
>  
> -static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> -		void *cpu_addr, dma_addr_t dma_addr, size_t size,
> -		unsigned long attrs)
> +int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> +		   void *cpu_addr, dma_addr_t dma_addr, size_t size,
> +		   unsigned long attrs)
>  {
>  	unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
>  	unsigned long pfn, off = vma->vm_pgoff;
> @@ -1673,9 +1676,9 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
>  			       vma->vm_page_prot);
>  }
>  
> -static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
> -		void *cpu_addr, dma_addr_t dma_addr, size_t size,
> -		unsigned long attrs)
> +int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
> +			  void *cpu_addr, dma_addr_t dma_addr, size_t size,
> +			  unsigned long attrs)
>  {
>  	struct page *page;
>  	int ret;
> @@ -1700,19 +1703,19 @@ static int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
>  	return ret;
>  }
>  
> -static unsigned long iommu_dma_get_merge_boundary(struct device *dev)
> +unsigned long iommu_dma_get_merge_boundary(struct device *dev)
>  {
>  	struct iommu_domain *domain = iommu_get_dma_domain(dev);
>  
>  	return (1UL << __ffs(domain->pgsize_bitmap)) - 1;
>  }
>  
> -static size_t iommu_dma_opt_mapping_size(void)
> +size_t iommu_dma_opt_mapping_size(void)
>  {
>  	return iova_rcache_range();
>  }
>  
> -static size_t iommu_dma_max_mapping_size(struct device *dev)
> +size_t iommu_dma_max_mapping_size(struct device *dev)
>  {
>  	if (dev_is_untrusted(dev))
>  		return swiotlb_max_mapping_size(dev);
> @@ -1720,32 +1723,6 @@ static size_t iommu_dma_max_mapping_size(struct device *dev)
>  	return SIZE_MAX;
>  }
>  
> -static const struct dma_map_ops iommu_dma_ops = {
> -	.flags			= DMA_F_PCI_P2PDMA_SUPPORTED |
> -				  DMA_F_CAN_SKIP_SYNC,
> -	.alloc			= iommu_dma_alloc,
> -	.free			= iommu_dma_free,
> -	.alloc_pages_op		= dma_common_alloc_pages,
> -	.free_pages		= dma_common_free_pages,
> -	.alloc_noncontiguous	= iommu_dma_alloc_noncontiguous,
> -	.free_noncontiguous	= iommu_dma_free_noncontiguous,
> -	.mmap			= iommu_dma_mmap,
> -	.get_sgtable		= iommu_dma_get_sgtable,
> -	.map_page		= iommu_dma_map_page,
> -	.unmap_page		= iommu_dma_unmap_page,
> -	.map_sg			= iommu_dma_map_sg,
> -	.unmap_sg		= iommu_dma_unmap_sg,
> -	.sync_single_for_cpu	= iommu_dma_sync_single_for_cpu,
> -	.sync_single_for_device	= iommu_dma_sync_single_for_device,
> -	.sync_sg_for_cpu	= iommu_dma_sync_sg_for_cpu,
> -	.sync_sg_for_device	= iommu_dma_sync_sg_for_device,
> -	.map_resource		= iommu_dma_map_resource,
> -	.unmap_resource		= iommu_dma_unmap_resource,
> -	.get_merge_boundary	= iommu_dma_get_merge_boundary,
> -	.opt_mapping_size	= iommu_dma_opt_mapping_size,
> -	.max_mapping_size       = iommu_dma_max_mapping_size,
> -};
> -
>  void iommu_setup_dma_ops(struct device *dev)
>  {
>  	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
> @@ -1756,10 +1733,10 @@ void iommu_setup_dma_ops(struct device *dev)
>  	if (iommu_is_dma_domain(domain)) {
>  		if (iommu_dma_init_domain(domain, dev))
>  			goto out_err;
> -		dev->dma_ops = &iommu_dma_ops;
> -	} else if (dev->dma_ops == &iommu_dma_ops) {
> +		dev->dma_iommu = true;
> +	} else if (dev->dma_iommu) {
>  		/* Clean up if we've switched *from* a DMA domain */
> -		dev->dma_ops = NULL;
> +		dev->dma_iommu = false;
>  	}
>  
>  	return;
> diff --git a/include/linux/device.h b/include/linux/device.h
> index ace039151cb8..7fa1e40b617a 100644
> --- a/include/linux/device.h
> +++ b/include/linux/device.h
> @@ -822,6 +822,9 @@ struct device {
>  #ifdef CONFIG_DMA_NEED_SYNC
>  	bool			dma_skip_sync:1;
>  #endif
> +#ifdef CONFIG_IOMMU_DMA
> +	bool			dma_iommu : 1;
> +#endif
>  };
>  
>  /**
> diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
> index 02a1c825896b..077b15c93bb8 100644
> --- a/include/linux/dma-map-ops.h
> +++ b/include/linux/dma-map-ops.h
> @@ -13,20 +13,7 @@
>  struct cma;
>  struct iommu_ops;
>  
> -/*
> - * Values for struct dma_map_ops.flags:
> - *
> - * DMA_F_PCI_P2PDMA_SUPPORTED: Indicates the dma_map_ops implementation can
> - * handle PCI P2PDMA pages in the map_sg/unmap_sg operation.
> - * DMA_F_CAN_SKIP_SYNC: DMA sync operations can be skipped if the device is
> - * coherent and it's not an SWIOTLB buffer.
> - */
> -#define DMA_F_PCI_P2PDMA_SUPPORTED     (1 << 0)
> -#define DMA_F_CAN_SKIP_SYNC            (1 << 1)
> -
>  struct dma_map_ops {
> -	unsigned int flags;
> -
>  	void *(*alloc)(struct device *dev, size_t size,
>  			dma_addr_t *dma_handle, gfp_t gfp,
>  			unsigned long attrs);
> diff --git a/include/linux/iommu-dma.h b/include/linux/iommu-dma.h
> new file mode 100644
> index 000000000000..622232fc9510
> --- /dev/null
> +++ b/include/linux/iommu-dma.h
> @@ -0,0 +1,169 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES. All rights reserved
> + *
> + * DMA operations that map physical memory through IOMMU.
> + */
> +#ifndef _LINUX_IOMMU_DMA_H
> +#define _LINUX_IOMMU_DMA_H
> +
> +#include <linux/dma-direction.h>
> +
> +#ifdef CONFIG_IOMMU_DMA
> +dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> +			      unsigned long offset, size_t size,
> +			      enum dma_data_direction dir, unsigned long attrs);
> +void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
> +			  size_t size, enum dma_data_direction dir,
> +			  unsigned long attrs);
> +int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
> +		     enum dma_data_direction dir, unsigned long attrs);
> +void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
> +			enum dma_data_direction dir, unsigned long attrs);
> +void *iommu_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,
> +		      gfp_t gfp, unsigned long attrs);
> +int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> +		   void *cpu_addr, dma_addr_t dma_addr,
> +		   size_t size, unsigned long attrs);
> +int iommu_dma_get_sgtable(struct device *dev, struct sg_table *sgt,
> +			  void *cpu_addr, dma_addr_t dma_addr, size_t size,
> +			  unsigned long attrs);
> +unsigned long iommu_dma_get_merge_boundary(struct device *dev);
> +size_t iommu_dma_opt_mapping_size(void);
> +size_t iommu_dma_max_mapping_size(struct device *dev);
> +void iommu_dma_free(struct device *dev, size_t size, void *cpu_addr,
> +		    dma_addr_t handle, unsigned long attrs);
> +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
> +				  size_t size, enum dma_data_direction dir,
> +				  unsigned long attrs);
> +void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
> +			      size_t size, enum dma_data_direction dir,
> +			      unsigned long attrs);
> +struct sg_table *iommu_dma_alloc_noncontiguous(struct device *dev, size_t size,
> +					       enum dma_data_direction dir,
> +					       gfp_t gfp, unsigned long attrs);
> +void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
> +				  struct sg_table *sgt,
> +				  enum dma_data_direction dir);
> +void iommu_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
> +				   size_t size, enum dma_data_direction dir);
> +void iommu_dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle,
> +				      size_t size, enum dma_data_direction dir);
> +void iommu_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
> +			       int nelems, enum dma_data_direction dir);
> +void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
> +				  int nelems, enum dma_data_direction dir);
> +#else
> +static inline dma_addr_t iommu_dma_map_page(struct device *dev,
> +					    struct page *page,
> +					    unsigned long offset, size_t size,
> +					    enum dma_data_direction dir,
> +					    unsigned long attrs)
> +{
> +	return DMA_MAPPING_ERROR;
> +}
> +static inline void iommu_dma_unmap_page(struct device *dev,
> +					dma_addr_t dma_handle, size_t size,
> +					enum dma_data_direction dir,
> +					unsigned long attrs)
> +{
> +}
> +static inline int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg,
> +				   int nents, enum dma_data_direction dir,
> +				   unsigned long attrs)
> +{
> +	return -EINVAL;
> +}
> +static inline void iommu_dma_unmap_sg(struct device *dev,
> +				      struct scatterlist *sg, int nents,
> +				      enum dma_data_direction dir,
> +				      unsigned long attrs)
> +{
> +}
> +static inline void *iommu_dma_alloc(struct device *dev, size_t size,
> +				    dma_addr_t *handle, gfp_t gfp,
> +				    unsigned long attrs)
> +{
> +	return NULL;
> +}
> +static inline int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
> +				 void *cpu_addr, dma_addr_t dma_addr,
> +				 size_t size, unsigned long attrs)
> +{
> +	return -EINVAL;
> +}
> +static inline int iommu_dma_get_sgtable(struct device *dev,
> +					struct sg_table *sgt, void *cpu_addr,
> +					dma_addr_t dma_addr, size_t size,
> +					unsigned long attrs)
> +{
> +	return -EINVAL;
> +}
> +static inline unsigned long iommu_dma_get_merge_boundary(struct device *dev)
> +{
> +	return 0;
> +}
> +static inline size_t iommu_dma_opt_mapping_size(void)
> +{
> +	return 0;
> +}
> +static inline size_t iommu_dma_max_mapping_size(struct device *dev)
> +{
> +	return 0;
> +}
> +static inline void iommu_dma_free(struct device *dev, size_t size,
> +				  void *cpu_addr, dma_addr_t handle,
> +				  unsigned long attrs)
> +{
> +}
> +static inline dma_addr_t iommu_dma_map_resource(struct device *dev,
> +						phys_addr_t phys, size_t size,
> +						enum dma_data_direction dir,
> +						unsigned long attrs)
> +{
> +	return DMA_MAPPING_ERROR;
> +}
> +static inline void iommu_dma_unmap_resource(struct device *dev,
> +					    dma_addr_t handle, size_t size,
> +					    enum dma_data_direction dir,
> +					    unsigned long attrs)
> +{
> +}
> +static inline struct sg_table *
> +iommu_dma_alloc_noncontiguous(struct device *dev, size_t size,
> +			      enum dma_data_direction dir, gfp_t gfp,
> +			      unsigned long attrs)
> +{
> +	return NULL;
> +}
> +static inline void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
> +						struct sg_table *sgt,
> +						enum dma_data_direction dir)
> +{
> +}
> +static inline void iommu_dma_sync_single_for_cpu(struct device *dev,
> +						 dma_addr_t dma_handle,
> +						 size_t size,
> +						 enum dma_data_direction dir)
> +{
> +}
> +static inline void iommu_dma_sync_single_for_device(struct device *dev,
> +						    dma_addr_t dma_handle,
> +						    size_t size,
> +						    enum dma_data_direction dir)
> +{
> +}
> +static inline void iommu_dma_sync_sg_for_cpu(struct device *dev,
> +					     struct scatterlist *sgl,
> +					     int nelems,
> +					     enum dma_data_direction dir)
> +{
> +}
> +static inline void iommu_dma_sync_sg_for_device(struct device *dev,
> +						struct scatterlist *sgl,
> +						int nelems,
> +						enum dma_data_direction dir)
> +{
> +}
> +#endif /* CONFIG_IOMMU_DMA */
> +#endif /* _LINUX_IOMMU_DMA_H */
> diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
> index 6832fd6f0796..feaa69c35f79 100644
> --- a/kernel/dma/mapping.c
> +++ b/kernel/dma/mapping.c
> @@ -8,6 +8,7 @@
>  #include <linux/memblock.h> /* for max_pfn */
>  #include <linux/acpi.h>
>  #include <linux/dma-map-ops.h>
> +#include <linux/iommu-dma.h>
>  #include <linux/export.h>
>  #include <linux/gfp.h>
>  #include <linux/kmsan.h>
> @@ -113,12 +114,24 @@ void *dmam_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  }
>  EXPORT_SYMBOL(dmam_alloc_attrs);
>  
> +static inline bool dma_is_default_iommu(struct device *dev)
> +{
> +#ifdef CONFIG_IOMMU_DMA
> +	return dev->dma_iommu;
> +#else
> +	return false;
> +#endif
> +}
> +
>  static bool dma_go_direct(struct device *dev, dma_addr_t mask,
>  		const struct dma_map_ops *ops)
>  {
> -	if (likely(!ops))
> +	WARN_ON_ONCE(ops && dma_is_default_iommu(dev));
> +	if (likely(!ops) && !dma_is_default_iommu(dev))
>  		return true;
> +
>  #ifdef CONFIG_DMA_OPS_BYPASS
> +	WARN_ON_ONCE(dev->dma_ops_bypass && dma_is_default_iommu(dev));
>  	if (dev->dma_ops_bypass)
>  		return min_not_zero(mask, dev->bus_dma_limit) >=
>  			    dma_direct_get_required_mask(dev);
> @@ -159,6 +172,8 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
>  	if (dma_map_direct(dev, ops) ||
>  	    arch_dma_map_page_direct(dev, page_to_phys(page) + offset + size))
>  		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		addr = iommu_dma_map_page(dev, page, offset, size, dir, attrs);
>  	else
>  		addr = ops->map_page(dev, page, offset, size, dir, attrs);
>  	kmsan_handle_dma(page, offset, size, dir);
> @@ -177,6 +192,8 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
>  	if (dma_map_direct(dev, ops) ||
>  	    arch_dma_unmap_page_direct(dev, addr + size))
>  		dma_direct_unmap_page(dev, addr, size, dir, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_unmap_page(dev, addr, size, dir, attrs);
>  	else
>  		ops->unmap_page(dev, addr, size, dir, attrs);
>  	debug_dma_unmap_page(dev, addr, size, dir);
> @@ -197,6 +214,8 @@ static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
>  	if (dma_map_direct(dev, ops) ||
>  	    arch_dma_map_sg_direct(dev, sg, nents))
>  		ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		ents = iommu_dma_map_sg(dev, sg, nents, dir, attrs);
>  	else
>  		ents = ops->map_sg(dev, sg, nents, dir, attrs);
>  
> @@ -291,6 +310,8 @@ void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
>  	if (dma_map_direct(dev, ops) ||
>  	    arch_dma_unmap_sg_direct(dev, sg, nents))
>  		dma_direct_unmap_sg(dev, sg, nents, dir, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_unmap_sg(dev, sg, nents, dir, attrs);
>  	else
>  		ops->unmap_sg(dev, sg, nents, dir, attrs);
>  }
> @@ -309,6 +330,8 @@ dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
>  
>  	if (dma_map_direct(dev, ops))
>  		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		addr = iommu_dma_map_resource(dev, phys_addr, size, dir, attrs);
>  	else if (ops->map_resource)
>  		addr = ops->map_resource(dev, phys_addr, size, dir, attrs);
>  
> @@ -323,8 +346,12 @@ void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
>  
>  	BUG_ON(!valid_dma_direction(dir));
> -	if (!dma_map_direct(dev, ops) && ops->unmap_resource)
> -		ops->unmap_resource(dev, addr, size, dir, attrs);
> +	if (!dma_map_direct(dev, ops)) {
> +		if (dma_is_default_iommu(dev))
> +			iommu_dma_unmap_resource(dev, addr, size, dir, attrs);
> +		else if (ops->unmap_resource)
> +			ops->unmap_resource(dev, addr, size, dir, attrs);
> +	}
>  	debug_dma_unmap_resource(dev, addr, size, dir);
>  }
>  EXPORT_SYMBOL(dma_unmap_resource);
> @@ -338,6 +365,8 @@ void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
>  	BUG_ON(!valid_dma_direction(dir));
>  	if (dma_map_direct(dev, ops))
>  		dma_direct_sync_single_for_cpu(dev, addr, size, dir);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_sync_single_for_cpu(dev, addr, size, dir);
>  	else if (ops->sync_single_for_cpu)
>  		ops->sync_single_for_cpu(dev, addr, size, dir);
>  	debug_dma_sync_single_for_cpu(dev, addr, size, dir);
> @@ -352,6 +381,8 @@ void __dma_sync_single_for_device(struct device *dev, dma_addr_t addr,
>  	BUG_ON(!valid_dma_direction(dir));
>  	if (dma_map_direct(dev, ops))
>  		dma_direct_sync_single_for_device(dev, addr, size, dir);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_sync_single_for_device(dev, addr, size, dir);
>  	else if (ops->sync_single_for_device)
>  		ops->sync_single_for_device(dev, addr, size, dir);
>  	debug_dma_sync_single_for_device(dev, addr, size, dir);
> @@ -366,6 +397,8 @@ void __dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
>  	BUG_ON(!valid_dma_direction(dir));
>  	if (dma_map_direct(dev, ops))
>  		dma_direct_sync_sg_for_cpu(dev, sg, nelems, dir);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
>  	else if (ops->sync_sg_for_cpu)
>  		ops->sync_sg_for_cpu(dev, sg, nelems, dir);
>  	debug_dma_sync_sg_for_cpu(dev, sg, nelems, dir);
> @@ -380,6 +413,8 @@ void __dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
>  	BUG_ON(!valid_dma_direction(dir));
>  	if (dma_map_direct(dev, ops))
>  		dma_direct_sync_sg_for_device(dev, sg, nelems, dir);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_sync_sg_for_device(dev, sg, nelems, dir);
>  	else if (ops->sync_sg_for_device)
>  		ops->sync_sg_for_device(dev, sg, nelems, dir);
>  	debug_dma_sync_sg_for_device(dev, sg, nelems, dir);
> @@ -405,7 +440,7 @@ static void dma_setup_need_sync(struct device *dev)
>  {
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
>  
> -	if (dma_map_direct(dev, ops) || (ops->flags & DMA_F_CAN_SKIP_SYNC))
> +	if (dma_map_direct(dev, ops) || dma_is_default_iommu(dev))
>  		/*
>  		 * dma_skip_sync will be reset to %false on first SWIOTLB buffer
>  		 * mapping, if any. During the device initialization, it's
> @@ -446,6 +481,9 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
>  	if (dma_alloc_direct(dev, ops))
>  		return dma_direct_get_sgtable(dev, sgt, cpu_addr, dma_addr,
>  				size, attrs);
> +	if (dma_is_default_iommu(dev))
> +		return iommu_dma_get_sgtable(dev, sgt, cpu_addr, dma_addr,
> +				size, attrs);
>  	if (!ops->get_sgtable)
>  		return -ENXIO;
>  	return ops->get_sgtable(dev, sgt, cpu_addr, dma_addr, size, attrs);
> @@ -482,6 +520,8 @@ bool dma_can_mmap(struct device *dev)
>  
>  	if (dma_alloc_direct(dev, ops))
>  		return dma_direct_can_mmap(dev);
> +	if (dma_is_default_iommu(dev))
> +		return true;
>  	return ops->mmap != NULL;
>  }
>  EXPORT_SYMBOL_GPL(dma_can_mmap);
> @@ -508,6 +548,9 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
>  	if (dma_alloc_direct(dev, ops))
>  		return dma_direct_mmap(dev, vma, cpu_addr, dma_addr, size,
>  				attrs);
> +	if (dma_is_default_iommu(dev))
> +		return iommu_dma_mmap(dev, vma, cpu_addr, dma_addr, size,
> +				      attrs);
>  	if (!ops->mmap)
>  		return -ENXIO;
>  	return ops->mmap(dev, vma, cpu_addr, dma_addr, size, attrs);
> @@ -559,6 +602,8 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
>  
>  	if (dma_alloc_direct(dev, ops))
>  		cpu_addr = dma_direct_alloc(dev, size, dma_handle, flag, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		cpu_addr = iommu_dma_alloc(dev, size, dma_handle, flag, attrs);
>  	else if (ops->alloc)
>  		cpu_addr = ops->alloc(dev, size, dma_handle, flag, attrs);
>  	else
> @@ -591,6 +636,8 @@ void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
>  	debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);
>  	if (dma_alloc_direct(dev, ops))
>  		dma_direct_free(dev, size, cpu_addr, dma_handle, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_free(dev, size, cpu_addr, dma_handle, attrs);
>  	else if (ops->free)
>  		ops->free(dev, size, cpu_addr, dma_handle, attrs);
>  }
> @@ -611,6 +658,8 @@ static struct page *__dma_alloc_pages(struct device *dev, size_t size,
>  	size = PAGE_ALIGN(size);
>  	if (dma_alloc_direct(dev, ops))
>  		return dma_direct_alloc_pages(dev, size, dma_handle, dir, gfp);
> +	if (dma_is_default_iommu(dev))
> +		return dma_common_alloc_pages(dev, size, dma_handle, dir, gfp);
>  	if (!ops->alloc_pages_op)
>  		return NULL;
>  	return ops->alloc_pages_op(dev, size, dma_handle, dir, gfp);
> @@ -635,6 +684,8 @@ static void __dma_free_pages(struct device *dev, size_t size, struct page *page,
>  	size = PAGE_ALIGN(size);
>  	if (dma_alloc_direct(dev, ops))
>  		dma_direct_free_pages(dev, size, page, dma_handle, dir);
> +	else if (dma_is_default_iommu(dev))
> +		dma_common_free_pages(dev, size, page, dma_handle, dir);
>  	else if (ops->free_pages)
>  		ops->free_pages(dev, size, page, dma_handle, dir);
>  }
> @@ -697,6 +748,8 @@ struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size,
>  
>  	if (ops && ops->alloc_noncontiguous)
>  		sgt = ops->alloc_noncontiguous(dev, size, dir, gfp, attrs);
> +	else if (dma_is_default_iommu(dev))
> +		sgt = iommu_dma_alloc_noncontiguous(dev, size, dir, gfp, attrs);
>  	else
>  		sgt = alloc_single_sgt(dev, size, dir, gfp);
>  
> @@ -725,6 +778,8 @@ void dma_free_noncontiguous(struct device *dev, size_t size,
>  	debug_dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, dir);
>  	if (ops && ops->free_noncontiguous)
>  		ops->free_noncontiguous(dev, size, sgt, dir);
> +	else if (dma_is_default_iommu(dev))
> +		iommu_dma_free_noncontiguous(dev, size, sgt, dir);
>  	else
>  		free_single_sgt(dev, size, sgt, dir);
>  }
> @@ -787,17 +842,14 @@ bool dma_pci_p2pdma_supported(struct device *dev)
>  {
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
>  
> -	/* if ops is not set, dma direct will be used which supports P2PDMA */
> -	if (!ops)
> -		return true;
> -
>  	/*
>  	 * Note: dma_ops_bypass is not checked here because P2PDMA should
>  	 * not be used with dma mapping ops that do not have support even
>  	 * if the specific device is bypassing them.
>  	 */
>  
> -	return ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED;
> +	/* if ops is not set, dma direct and default IOMMU support P2PDMA */
> +	return (!ops || dma_is_default_iommu(dev));
>  }
>  EXPORT_SYMBOL_GPL(dma_pci_p2pdma_supported);
>  
> @@ -865,6 +917,8 @@ size_t dma_max_mapping_size(struct device *dev)
>  
>  	if (dma_map_direct(dev, ops))
>  		size = dma_direct_max_mapping_size(dev);
> +	else if (dma_is_default_iommu(dev))
> +		size = iommu_dma_max_mapping_size(dev);
>  	else if (ops && ops->max_mapping_size)
>  		size = ops->max_mapping_size(dev);
>  
> @@ -877,9 +931,10 @@ size_t dma_opt_mapping_size(struct device *dev)
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
>  	size_t size = SIZE_MAX;
>  
> -	if (ops && ops->opt_mapping_size)
> +	if (dma_is_default_iommu(dev))
> +		size = iommu_dma_opt_mapping_size();
> +	else if (ops && ops->opt_mapping_size)
>  		size = ops->opt_mapping_size();
> -
>  	return min(dma_max_mapping_size(dev), size);
>  }
>  EXPORT_SYMBOL_GPL(dma_opt_mapping_size);
> @@ -888,7 +943,12 @@ unsigned long dma_get_merge_boundary(struct device *dev)
>  {
>  	const struct dma_map_ops *ops = get_dma_ops(dev);
>  
> -	if (!ops || !ops->get_merge_boundary)
> +	if (!ops)
> +		return 0;	/* can't merge */
> +	if (dma_is_default_iommu(dev))
> +		return iommu_dma_get_merge_boundary(dev);
> +
> +	if (!ops->get_merge_boundary)
>  		return 0;	/* can't merge */
>  
>  	return ops->get_merge_boundary(dev);
> -- 
> 2.45.2
> 

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Leon Romanovsky]

On Mon, Jul 29, 2024 at 12:41:12PM +0000, Mostafa Saleh wrote:
> Hi Leon,
> 
> On Wed, Jul 17, 2024 at 03:37:11PM +0300, Leon Romanovsky wrote:
> > From: Leon Romanovsky <leonro@nvidia.com>
> > 
> > Most of the arch DMA ops (which often, but not  always, involve
> > some sort of IOMMU) are using the same DMA operations. These DMA
> > operations are default ones implemented in drivers/iomem/dma-iommu.c.
> > 
> > So let's make sure to call them directly without need to perform function
> > pointers dereference.
> 
> Just out of curiosity, is there any observed improvement from that?
> As from my experience the DMA-IOMMU path is quite dense so it won't
> be senstive to such micro-optimizations.

DMA-IOMMU no, but NVMe driver which uses DMA-API in datapath will
potentially benefit from this change.

I personally used this change to simplify my "DMA split ... " series [1].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/leon/linux-rdma.git/log/?h=dma-split-v2

Thanks

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Christoph Hellwig]

On Mon, Jul 29, 2024 at 12:41:12PM +0000, Mostafa Saleh wrote:
> Just out of curiosity, is there any observed improvement from that?
> As from my experience the DMA-IOMMU path is quite dense so it won't
> be senstive to such micro-optimizations.

We are trying to gradually fix this.   Part of that is adding not even
more indirect calls for the next generation map API.  But another totally
unrelated part is that we can compile out the dma ops entirely for
common configs, which I really want because people are badly abusing it.

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Leon Romanovsky]

On Mon, Jul 29, 2024 at 07:15:18PM +0200, Christoph Hellwig wrote:
> On Mon, Jul 29, 2024 at 12:41:12PM +0000, Mostafa Saleh wrote:
> > Just out of curiosity, is there any observed improvement from that?
> > As from my experience the DMA-IOMMU path is quite dense so it won't
> > be senstive to such micro-optimizations.
> 
> We are trying to gradually fix this.   Part of that is adding not even
> more indirect calls for the next generation map API.  But another totally
> unrelated part is that we can compile out the dma ops entirely for
> common configs, which I really want because people are badly abusing it.

Christoph,

This is good remark, should I add this to the commit message and send v5?
v4: https://lore.kernel.org/all/cover.1721818168.git.leon@kernel.org/

Thanks

Re: [PATCH v2 2/2] dma: add IOMMU static calls with clear default ops

[Christoph Hellwig]

On Tue, Jul 30, 2024 at 11:16:37AM +0300, Leon Romanovsky wrote:
> This is good remark, should I add this to the commit message and send v5?

I can just add it.  I'm fine with the current series except for a little
cosmetic coding style fixup I can take care of, but I'd really like to
see an Ack from Greg for the new bit in struct device, and a review
from Robin.