[PATCH v2 00/16] dma-mapping: migrate to physical address-based API

[PATCH v2 00/16] dma-mapping: migrate to physical address-based API

[Leon Romanovsky]

Changelog:
v2:
 * Used commit messages and cover letter from Jason
 * Moved setting IOMMU_MMIO flag to dma_info_to_prot function
 * Micro-optimized the code
 * Rebased code on v6.17-rc1
v1: https://lore.kernel.org/all/cover.1754292567.git.leon@kernel.org
 * Added new DMA_ATTR_MMIO attribute to indicate
   PCI_P2PDMA_MAP_THRU_HOST_BRIDGE path.
 * Rewrote dma_map_* functions to use thus new attribute
v0: https://lore.kernel.org/all/cover.1750854543.git.leon@kernel.org/
------------------------------------------------------------------------

This series refactors the DMA mapping to use physical addresses
as the primary interface instead of page+offset parameters. This
change aligns the DMA API with the underlying hardware reality where
DMA operations work with physical addresses, not page structures.

The series maintains export symbol backward compatibility by keeping
the old page-based API as wrapper functions around the new physical
address-based implementations.

This series refactors the DMA mapping API to provide a phys_addr_t
based, and struct-page free, external API that can handle all the
mapping cases we want in modern systems:

 - struct page based cachable DRAM
 - struct page MEMORY_DEVICE_PCI_P2PDMA PCI peer to peer non-cachable
   MMIO
 - struct page-less PCI peer to peer non-cachable MMIO
 - struct page-less "resource" MMIO

Overall this gets much closer to Matthew's long term wish for
struct-pageless IO to cachable DRAM. The remaining primary work would
be in the mm side to allow kmap_local_pfn()/phys_to_virt() to work on
phys_addr_t without a struct page.

The general design is to remove struct page usage entirely from the
DMA API inner layers. For flows that need to have a KVA for the
physical address they can use kmap_local_pfn() or phys_to_virt(). This
isolates the struct page requirements to MM code only. Long term all
removals of struct page usage are supporting Matthew's memdesc
project which seeks to substantially transform how struct page works.

Instead make the DMA API internals work on phys_addr_t. Internally
there are still dedicated 'page' and 'resource' flows, except they are
now distinguished by a new DMA_ATTR_MMIO instead of by callchain. Both
flows use the same phys_addr_t.

When DMA_ATTR_MMIO is specified things work similar to the existing
'resource' flow. kmap_local_pfn(), phys_to_virt(), phys_to_page(),
pfn_valid(), etc are never called on the phys_addr_t. This requires
rejecting any configuration that would need swiotlb. CPU cache
flushing is not required, and avoided, as ATTR_MMIO also indicates the
address have no cachable mappings. This effectively removes any
DMA API side requirement to have struct page when DMA_ATTR_MMIO is
used.

In the !DMA_ATTR_MMIO mode things work similarly to the 'page' flow,
except on the common path of no cache flush, no swiotlb it never
touches a struct page. When cache flushing or swiotlb copying
kmap_local_pfn()/phys_to_virt() are used to get a KVA for CPU
usage. This was already the case on the unmap side, now the map side
is symmetric.

Callers are adjusted to set DMA_ATTR_MMIO. Existing 'resource' users
must set it. The existing struct page based MEMORY_DEVICE_PCI_P2PDMA
path must also set it. This corrects some existing bugs where iommu
mappings for P2P MMIO were improperly marked IOMMU_CACHE.

Since ATTR_MMIO is made to work with all the existing DMA map entry
points, particularly dma_iova_link(), this finally allows a way to use
the new DMA API to map PCI P2P MMIO without creating struct page. The
VFIO DMABUF series demonstrates how this works. This is intended to
replace the incorrect driver use of dma_map_resource() on PCI BAR
addresses.

This series does the core code and modern flows. A followup series
will give the same treatment to the legacy dma_ops implementation.

Thanks

Leon Romanovsky (16):
  dma-mapping: introduce new DMA attribute to indicate MMIO memory
  iommu/dma: implement DMA_ATTR_MMIO for dma_iova_link().
  dma-debug: refactor to use physical addresses for page mapping
  dma-mapping: rename trace_dma_*map_page to trace_dma_*map_phys
  iommu/dma: rename iommu_dma_*map_page to iommu_dma_*map_phys
  iommu/dma: extend iommu_dma_*map_phys API to handle MMIO memory
  dma-mapping: convert dma_direct_*map_page to be phys_addr_t based
  kmsan: convert kmsan_handle_dma to use physical addresses
  dma-mapping: handle MMIO flow in dma_map|unmap_page
  xen: swiotlb: Open code map_resource callback
  dma-mapping: export new dma_*map_phys() interface
  mm/hmm: migrate to physical address-based DMA mapping API
  mm/hmm: properly take MMIO path
  block-dma: migrate to dma_map_phys instead of map_page
  block-dma: properly take MMIO path
  nvme-pci: unmap MMIO pages with appropriate interface

 Documentation/core-api/dma-api.rst        |   4 +-
 Documentation/core-api/dma-attributes.rst |  18 ++++
 arch/powerpc/kernel/dma-iommu.c           |   4 +-
 block/blk-mq-dma.c                        |  15 ++-
 drivers/iommu/dma-iommu.c                 |  61 ++++++------
 drivers/nvme/host/pci.c                   |  18 +++-
 drivers/virtio/virtio_ring.c              |   4 +-
 drivers/xen/swiotlb-xen.c                 |  21 +++-
 include/linux/blk-mq-dma.h                |   6 +-
 include/linux/blk_types.h                 |   2 +
 include/linux/dma-direct.h                |   2 -
 include/linux/dma-map-ops.h               |   8 +-
 include/linux/dma-mapping.h               |  33 ++++++
 include/linux/iommu-dma.h                 |  11 +-
 include/linux/kmsan.h                     |  12 ++-
 include/trace/events/dma.h                |   9 +-
 kernel/dma/debug.c                        |  71 ++++---------
 kernel/dma/debug.h                        |  37 ++-----
 kernel/dma/direct.c                       |  22 +---
 kernel/dma/direct.h                       |  52 ++++++----
 kernel/dma/mapping.c                      | 116 +++++++++++++---------
 kernel/dma/ops_helpers.c                  |   6 +-
 mm/hmm.c                                  |  19 ++--
 mm/kmsan/hooks.c                          |  36 +++++--
 rust/kernel/dma.rs                        |   3 +
 tools/virtio/linux/kmsan.h                |   2 +-
 26 files changed, 333 insertions(+), 259 deletions(-)

-- 
2.50.1

[PATCH v2 01/16] dma-mapping: introduce new DMA attribute to indicate MMIO memory

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

This patch introduces the DMA_ATTR_MMIO attribute to mark DMA buffers
that reside in memory-mapped I/O (MMIO) regions, such as device BARs
exposed through the host bridge, which are accessible for peer-to-peer
(P2P) DMA.

This attribute is especially useful for exporting device memory to other
devices for DMA without CPU involvement, and avoids unnecessary or
potentially detrimental CPU cache maintenance calls.

DMA_ATTR_MMIO is supposed to provide dma_map_resource() functionality
without need to call to special function and perform branching by
the callers.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 Documentation/core-api/dma-attributes.rst | 18 ++++++++++++++++++
 include/linux/dma-mapping.h               | 20 ++++++++++++++++++++
 include/trace/events/dma.h                |  3 ++-
 rust/kernel/dma.rs                        |  3 +++
 4 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst
index 1887d92e8e92..58a1528a9bb9 100644
--- a/Documentation/core-api/dma-attributes.rst
+++ b/Documentation/core-api/dma-attributes.rst
@@ -130,3 +130,21 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged
 subsystem that the buffer is fully accessible at the elevated privilege
 level (and ideally inaccessible or at least read-only at the
 lesser-privileged levels).
+
+DMA_ATTR_MMIO
+-------------
+
+This attribute indicates the physical address is not normal system
+memory. It may not be used with kmap*()/phys_to_virt()/phys_to_page()
+functions, it may not be cachable, and access using CPU load/store
+instructions may not be allowed.
+
+Usually this will be used to describe MMIO addresses, or other non
+cachable register addresses. When DMA mapping this sort of address we
+call the operation Peer to Peer as a one device is DMA'ing to another
+device. For PCI devices the p2pdma APIs must be used to determine if
+DMA_ATTR_MMIO is appropriate.
+
+For architectures that require cache flushing for DMA coherence
+DMA_ATTR_MMIO will not perform any cache flushing. The address
+provided must never be mapped cachable into the CPU.
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 55c03e5fe8cb..ead5514d389e 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -58,6 +58,26 @@
  */
 #define DMA_ATTR_PRIVILEGED		(1UL << 9)
 
+/*
+ * DMA_ATTR_MMIO - Indicates memory-mapped I/O (MMIO) region for DMA mapping
+ *
+ * This attribute indicates the physical address is not normal system
+ * memory. It may not be used with kmap*()/phys_to_virt()/phys_to_page()
+ * functions, it may not be cachable, and access using CPU load/store
+ * instructions may not be allowed.
+ *
+ * Usually this will be used to describe MMIO addresses, or other non
+ * cachable register addresses. When DMA mapping this sort of address we
+ * call the operation Peer to Peer as a one device is DMA'ing to another
+ * device. For PCI devices the p2pdma APIs must be used to determine if
+ * DMA_ATTR_MMIO is appropriate.
+ *
+ * For architectures that require cache flushing for DMA coherence
+ * DMA_ATTR_MMIO will not perform any cache flushing. The address
+ * provided must never be mapped cachable into the CPU.
+ */
+#define DMA_ATTR_MMIO		(1UL << 10)
+
 /*
  * A dma_addr_t can hold any valid DMA or bus address for the platform.  It can
  * be given to a device to use as a DMA source or target.  It is specific to a
diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h
index d8ddc27b6a7c..ee90d6f1dcf3 100644
--- a/include/trace/events/dma.h
+++ b/include/trace/events/dma.h
@@ -31,7 +31,8 @@ TRACE_DEFINE_ENUM(DMA_NONE);
 		{ DMA_ATTR_FORCE_CONTIGUOUS, "FORCE_CONTIGUOUS" }, \
 		{ DMA_ATTR_ALLOC_SINGLE_PAGES, "ALLOC_SINGLE_PAGES" }, \
 		{ DMA_ATTR_NO_WARN, "NO_WARN" }, \
-		{ DMA_ATTR_PRIVILEGED, "PRIVILEGED" })
+		{ DMA_ATTR_PRIVILEGED, "PRIVILEGED" }, \
+		{ DMA_ATTR_MMIO, "MMIO" })
 
 DECLARE_EVENT_CLASS(dma_map,
 	TP_PROTO(struct device *dev, phys_addr_t phys_addr, dma_addr_t dma_addr,
diff --git a/rust/kernel/dma.rs b/rust/kernel/dma.rs
index 2bc8ab51ec28..61d9eed7a786 100644
--- a/rust/kernel/dma.rs
+++ b/rust/kernel/dma.rs
@@ -242,6 +242,9 @@ pub mod attrs {
     /// Indicates that the buffer is fully accessible at an elevated privilege level (and
     /// ideally inaccessible or at least read-only at lesser-privileged levels).
     pub const DMA_ATTR_PRIVILEGED: Attrs = Attrs(bindings::DMA_ATTR_PRIVILEGED);
+
+    /// Indicates that the buffer is MMIO memory.
+    pub const DMA_ATTR_MMIO: Attrs = Attrs(bindings::DMA_ATTR_MMIO);
 }
 
 /// An abstraction of the `dma_alloc_coherent` API.
-- 
2.50.1

[PATCH v2 02/16] iommu/dma: implement DMA_ATTR_MMIO for dma_iova_link().

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

This will replace the hacky use of DMA_ATTR_SKIP_CPU_SYNC to avoid
touching the possibly non-KVA MMIO memory.

Also correct the incorrect caching attribute for the IOMMU, MMIO
memory should not be cachable inside the IOMMU mapping or it can
possibly create system problems. Set IOMMU_MMIO for DMA_ATTR_MMIO.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/iommu/dma-iommu.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index ea2ef53bd4fe..e1185ba73e23 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -724,7 +724,12 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, struct device *dev
 static int dma_info_to_prot(enum dma_data_direction dir, bool coherent,
 		     unsigned long attrs)
 {
-	int prot = coherent ? IOMMU_CACHE : 0;
+	int prot;
+
+	if (attrs & DMA_ATTR_MMIO)
+		prot = IOMMU_MMIO;
+	else
+		prot = coherent ? IOMMU_CACHE : 0;
 
 	if (attrs & DMA_ATTR_PRIVILEGED)
 		prot |= IOMMU_PRIV;
@@ -1838,12 +1843,13 @@ static int __dma_iova_link(struct device *dev, dma_addr_t addr,
 		unsigned long attrs)
 {
 	bool coherent = dev_is_dma_coherent(dev);
+	int prot = dma_info_to_prot(dir, coherent, attrs);
 
-	if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+	if (!coherent && !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO)))
 		arch_sync_dma_for_device(phys, size, dir);
 
 	return iommu_map_nosync(iommu_get_dma_domain(dev), addr, phys, size,
-			dma_info_to_prot(dir, coherent, attrs), GFP_ATOMIC);
+			prot, GFP_ATOMIC);
 }
 
 static int iommu_dma_iova_bounce_and_link(struct device *dev, dma_addr_t addr,
@@ -1949,9 +1955,13 @@ int dma_iova_link(struct device *dev, struct dma_iova_state *state,
 		return -EIO;
 
 	if (dev_use_swiotlb(dev, size, dir) &&
-	    iova_unaligned(iovad, phys, size))
+	    iova_unaligned(iovad, phys, size)) {
+		if (attrs & DMA_ATTR_MMIO)
+			return -EPERM;
+
 		return iommu_dma_iova_link_swiotlb(dev, state, phys, offset,
 				size, dir, attrs);
+	}
 
 	return __dma_iova_link(dev, state->addr + offset - iova_start_pad,
 			phys - iova_start_pad,
-- 
2.50.1

[PATCH v2 03/16] dma-debug: refactor to use physical addresses for page mapping

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Convert the DMA debug infrastructure from page-based to physical address-based
mapping as a preparation to rely on physical address for DMA mapping routines.

The refactoring renames debug_dma_map_page() to debug_dma_map_phys() and
changes its signature to accept a phys_addr_t parameter instead of struct page
and offset. Similarly, debug_dma_unmap_page() becomes debug_dma_unmap_phys().
A new dma_debug_phy type is introduced to distinguish physical address mappings
from other debug entry types. All callers throughout the codebase are updated
to pass physical addresses directly, eliminating the need for page-to-physical
conversion in the debug layer.

This refactoring eliminates the need to convert between page pointers and
physical addresses in the debug layer, making the code more efficient and
consistent with the DMA mapping API's physical address focus.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 Documentation/core-api/dma-api.rst |  4 ++--
 kernel/dma/debug.c                 | 28 +++++++++++++++++-----------
 kernel/dma/debug.h                 | 16 +++++++---------
 kernel/dma/mapping.c               | 15 ++++++++-------
 4 files changed, 34 insertions(+), 29 deletions(-)

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index 3087bea715ed..ca75b3541679 100644
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -761,7 +761,7 @@ example warning message may look like this::
 	[<ffffffff80235177>] find_busiest_group+0x207/0x8a0
 	[<ffffffff8064784f>] _spin_lock_irqsave+0x1f/0x50
 	[<ffffffff803c7ea3>] check_unmap+0x203/0x490
-	[<ffffffff803c8259>] debug_dma_unmap_page+0x49/0x50
+	[<ffffffff803c8259>] debug_dma_unmap_phys+0x49/0x50
 	[<ffffffff80485f26>] nv_tx_done_optimized+0xc6/0x2c0
 	[<ffffffff80486c13>] nv_nic_irq_optimized+0x73/0x2b0
 	[<ffffffff8026df84>] handle_IRQ_event+0x34/0x70
@@ -855,7 +855,7 @@ that a driver may be leaking mappings.
 dma-debug interface debug_dma_mapping_error() to debug drivers that fail
 to check DMA mapping errors on addresses returned by dma_map_single() and
 dma_map_page() interfaces. This interface clears a flag set by
-debug_dma_map_page() to indicate that dma_mapping_error() has been called by
+debug_dma_map_phys() to indicate that dma_mapping_error() has been called by
 the driver. When driver does unmap, debug_dma_unmap() checks the flag and if
 this flag is still set, prints warning message that includes call trace that
 leads up to the unmap. This interface can be called from dma_mapping_error()
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index e43c6de2bce4..da6734e3a4ce 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -39,6 +39,7 @@ enum {
 	dma_debug_sg,
 	dma_debug_coherent,
 	dma_debug_resource,
+	dma_debug_phy,
 };
 
 enum map_err_types {
@@ -141,6 +142,7 @@ static const char *type2name[] = {
 	[dma_debug_sg] = "scatter-gather",
 	[dma_debug_coherent] = "coherent",
 	[dma_debug_resource] = "resource",
+	[dma_debug_phy] = "phy",
 };
 
 static const char *dir2name[] = {
@@ -1201,9 +1203,8 @@ void debug_dma_map_single(struct device *dev, const void *addr,
 }
 EXPORT_SYMBOL(debug_dma_map_single);
 
-void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
-			size_t size, int direction, dma_addr_t dma_addr,
-			unsigned long attrs)
+void debug_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
+		int direction, dma_addr_t dma_addr, unsigned long attrs)
 {
 	struct dma_debug_entry *entry;
 
@@ -1218,19 +1219,24 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,
 		return;
 
 	entry->dev       = dev;
-	entry->type      = dma_debug_single;
-	entry->paddr	 = page_to_phys(page) + offset;
+	entry->type      = dma_debug_phy;
+	entry->paddr	 = phys;
 	entry->dev_addr  = dma_addr;
 	entry->size      = size;
 	entry->direction = direction;
 	entry->map_err_type = MAP_ERR_NOT_CHECKED;
 
-	check_for_stack(dev, page, offset);
+	if (!(attrs & DMA_ATTR_MMIO)) {
+		struct page *page = phys_to_page(phys);
+		size_t offset = offset_in_page(page);
 
-	if (!PageHighMem(page)) {
-		void *addr = page_address(page) + offset;
+		check_for_stack(dev, page, offset);
 
-		check_for_illegal_area(dev, addr, size);
+		if (!PageHighMem(page)) {
+			void *addr = page_address(page) + offset;
+
+			check_for_illegal_area(dev, addr, size);
+		}
 	}
 
 	add_dma_entry(entry, attrs);
@@ -1274,11 +1280,11 @@ void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
 }
 EXPORT_SYMBOL(debug_dma_mapping_error);
 
-void debug_dma_unmap_page(struct device *dev, dma_addr_t dma_addr,
+void debug_dma_unmap_phys(struct device *dev, dma_addr_t dma_addr,
 			  size_t size, int direction)
 {
 	struct dma_debug_entry ref = {
-		.type           = dma_debug_single,
+		.type           = dma_debug_phy,
 		.dev            = dev,
 		.dev_addr       = dma_addr,
 		.size           = size,
diff --git a/kernel/dma/debug.h b/kernel/dma/debug.h
index f525197d3cae..76adb42bffd5 100644
--- a/kernel/dma/debug.h
+++ b/kernel/dma/debug.h
@@ -9,12 +9,11 @@
 #define _KERNEL_DMA_DEBUG_H
 
 #ifdef CONFIG_DMA_API_DEBUG
-extern void debug_dma_map_page(struct device *dev, struct page *page,
-			       size_t offset, size_t size,
-			       int direction, dma_addr_t dma_addr,
+extern void debug_dma_map_phys(struct device *dev, phys_addr_t phys,
+			       size_t size, int direction, dma_addr_t dma_addr,
 			       unsigned long attrs);
 
-extern void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
+extern void debug_dma_unmap_phys(struct device *dev, dma_addr_t addr,
 				 size_t size, int direction);
 
 extern void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,
@@ -55,14 +54,13 @@ extern void debug_dma_sync_sg_for_device(struct device *dev,
 					 struct scatterlist *sg,
 					 int nelems, int direction);
 #else /* CONFIG_DMA_API_DEBUG */
-static inline void debug_dma_map_page(struct device *dev, struct page *page,
-				      size_t offset, size_t size,
-				      int direction, dma_addr_t dma_addr,
-				      unsigned long attrs)
+static inline void debug_dma_map_phys(struct device *dev, phys_addr_t phys,
+				      size_t size, int direction,
+				      dma_addr_t dma_addr, unsigned long attrs)
 {
 }
 
-static inline void debug_dma_unmap_page(struct device *dev, dma_addr_t addr,
+static inline void debug_dma_unmap_phys(struct device *dev, dma_addr_t addr,
 					size_t size, int direction)
 {
 }
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 107e4a4d251d..4c1dfbabb8ae 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -157,6 +157,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
+	phys_addr_t phys = page_to_phys(page) + offset;
 	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
@@ -165,16 +166,15 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		return DMA_MAPPING_ERROR;
 
 	if (dma_map_direct(dev, ops) ||
-	    arch_dma_map_page_direct(dev, page_to_phys(page) + offset + size))
+	    arch_dma_map_page_direct(dev, phys + size))
 		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
 	else if (use_dma_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);
-	trace_dma_map_page(dev, page_to_phys(page) + offset, addr, size, dir,
-			   attrs);
-	debug_dma_map_page(dev, page, offset, size, dir, addr, attrs);
+	trace_dma_map_page(dev, phys, addr, size, dir, attrs);
+	debug_dma_map_phys(dev, phys, size, dir, addr, attrs);
 
 	return addr;
 }
@@ -194,7 +194,7 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 	else
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	trace_dma_unmap_page(dev, addr, size, dir, attrs);
-	debug_dma_unmap_page(dev, addr, size, dir);
+	debug_dma_unmap_phys(dev, addr, size, dir);
 }
 EXPORT_SYMBOL(dma_unmap_page_attrs);
 
@@ -712,7 +712,8 @@ struct page *dma_alloc_pages(struct device *dev, size_t size,
 	if (page) {
 		trace_dma_alloc_pages(dev, page_to_virt(page), *dma_handle,
 				      size, dir, gfp, 0);
-		debug_dma_map_page(dev, page, 0, size, dir, *dma_handle, 0);
+		debug_dma_map_phys(dev, page_to_phys(page), size, dir,
+				   *dma_handle, 0);
 	} else {
 		trace_dma_alloc_pages(dev, NULL, 0, size, dir, gfp, 0);
 	}
@@ -738,7 +739,7 @@ void dma_free_pages(struct device *dev, size_t size, struct page *page,
 		dma_addr_t dma_handle, enum dma_data_direction dir)
 {
 	trace_dma_free_pages(dev, page_to_virt(page), dma_handle, size, dir, 0);
-	debug_dma_unmap_page(dev, dma_handle, size, dir);
+	debug_dma_unmap_phys(dev, dma_handle, size, dir);
 	__dma_free_pages(dev, size, page, dma_handle, dir);
 }
 EXPORT_SYMBOL_GPL(dma_free_pages);
-- 
2.50.1

[PATCH v2 04/16] dma-mapping: rename trace_dma_*map_page to trace_dma_*map_phys

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

As a preparation for following map_page -> map_phys API conversion,
let's rename trace_dma_*map_page() to be trace_dma_*map_phys().

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 include/trace/events/dma.h | 4 ++--
 kernel/dma/mapping.c       | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h
index ee90d6f1dcf3..84416c7d6bfa 100644
--- a/include/trace/events/dma.h
+++ b/include/trace/events/dma.h
@@ -72,7 +72,7 @@ DEFINE_EVENT(dma_map, name, \
 		 size_t size, enum dma_data_direction dir, unsigned long attrs), \
 	TP_ARGS(dev, phys_addr, dma_addr, size, dir, attrs))
 
-DEFINE_MAP_EVENT(dma_map_page);
+DEFINE_MAP_EVENT(dma_map_phys);
 DEFINE_MAP_EVENT(dma_map_resource);
 
 DECLARE_EVENT_CLASS(dma_unmap,
@@ -110,7 +110,7 @@ DEFINE_EVENT(dma_unmap, name, \
 		 enum dma_data_direction dir, unsigned long attrs), \
 	TP_ARGS(dev, addr, size, dir, attrs))
 
-DEFINE_UNMAP_EVENT(dma_unmap_page);
+DEFINE_UNMAP_EVENT(dma_unmap_phys);
 DEFINE_UNMAP_EVENT(dma_unmap_resource);
 
 DECLARE_EVENT_CLASS(dma_alloc_class,
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 4c1dfbabb8ae..fe1f0da6dc50 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -173,7 +173,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 	else
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
 	kmsan_handle_dma(page, offset, size, dir);
-	trace_dma_map_page(dev, phys, addr, size, dir, attrs);
+	trace_dma_map_phys(dev, phys, addr, size, dir, attrs);
 	debug_dma_map_phys(dev, phys, size, dir, addr, attrs);
 
 	return addr;
@@ -193,7 +193,7 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 		iommu_dma_unmap_page(dev, addr, size, dir, attrs);
 	else
 		ops->unmap_page(dev, addr, size, dir, attrs);
-	trace_dma_unmap_page(dev, addr, size, dir, attrs);
+	trace_dma_unmap_phys(dev, addr, size, dir, attrs);
 	debug_dma_unmap_phys(dev, addr, size, dir);
 }
 EXPORT_SYMBOL(dma_unmap_page_attrs);
-- 
2.50.1

[PATCH v2 05/16] iommu/dma: rename iommu_dma_*map_page to iommu_dma_*map_phys

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Rename the IOMMU DMA mapping functions to better reflect their actual
calling convention. The functions iommu_dma_map_page() and
iommu_dma_unmap_page() are renamed to iommu_dma_map_phys() and
iommu_dma_unmap_phys() respectively, as they already operate on physical
addresses rather than page structures.

The calling convention changes from accepting (struct page *page,
unsigned long offset) to (phys_addr_t phys), which eliminates the need
for page-to-physical address conversion within the functions. This
renaming prepares for the broader DMA API conversion from page-based
to physical address-based mapping throughout the kernel.

All callers are updated to pass physical addresses directly, including
dma_map_page_attrs(), scatterlist mapping functions, and DMA page
allocation helpers. The change simplifies the code by removing the
page_to_phys() + offset calculation that was previously done inside
the IOMMU functions.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/iommu/dma-iommu.c | 14 ++++++--------
 include/linux/iommu-dma.h |  7 +++----
 kernel/dma/mapping.c      |  4 ++--
 kernel/dma/ops_helpers.c  |  6 +++---
 4 files changed, 14 insertions(+), 17 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index e1185ba73e23..aea119f32f96 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1195,11 +1195,9 @@ static inline size_t iova_unaligned(struct iova_domain *iovad, phys_addr_t phys,
 	return iova_offset(iovad, phys | size);
 }
 
-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_phys(struct device *dev, phys_addr_t phys, 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);
 	int prot = dma_info_to_prot(dir, coherent, attrs);
 	struct iommu_domain *domain = iommu_get_dma_domain(dev);
@@ -1227,7 +1225,7 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
 	return iova;
 }
 
-void iommu_dma_unmap_page(struct device *dev, dma_addr_t dma_handle,
+void iommu_dma_unmap_phys(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);
@@ -1346,7 +1344,7 @@ static void iommu_dma_unmap_sg_swiotlb(struct device *dev, struct scatterlist *s
 	int i;
 
 	for_each_sg(sg, s, nents, i)
-		iommu_dma_unmap_page(dev, sg_dma_address(s),
+		iommu_dma_unmap_phys(dev, sg_dma_address(s),
 				sg_dma_len(s), dir, attrs);
 }
 
@@ -1359,8 +1357,8 @@ static int iommu_dma_map_sg_swiotlb(struct device *dev, struct scatterlist *sg,
 	sg_dma_mark_swiotlb(sg);
 
 	for_each_sg(sg, s, nents, i) {
-		sg_dma_address(s) = iommu_dma_map_page(dev, sg_page(s),
-				s->offset, s->length, dir, attrs);
+		sg_dma_address(s) = iommu_dma_map_phys(dev, sg_phys(s),
+				s->length, dir, attrs);
 		if (sg_dma_address(s) == DMA_MAPPING_ERROR)
 			goto out_unmap;
 		sg_dma_len(s) = s->length;
diff --git a/include/linux/iommu-dma.h b/include/linux/iommu-dma.h
index 508beaa44c39..485bdffed988 100644
--- a/include/linux/iommu-dma.h
+++ b/include/linux/iommu-dma.h
@@ -21,10 +21,9 @@ static inline bool use_dma_iommu(struct device *dev)
 }
 #endif /* 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,
+dma_addr_t iommu_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
+		enum dma_data_direction dir, unsigned long attrs);
+void iommu_dma_unmap_phys(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);
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index fe1f0da6dc50..58482536db9b 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -169,7 +169,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 	    arch_dma_map_page_direct(dev, phys + size))
 		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
 	else if (use_dma_iommu(dev))
-		addr = iommu_dma_map_page(dev, page, offset, size, dir, attrs);
+		addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
 	else
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
 	kmsan_handle_dma(page, offset, size, dir);
@@ -190,7 +190,7 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 	    arch_dma_unmap_page_direct(dev, addr + size))
 		dma_direct_unmap_page(dev, addr, size, dir, attrs);
 	else if (use_dma_iommu(dev))
-		iommu_dma_unmap_page(dev, addr, size, dir, attrs);
+		iommu_dma_unmap_phys(dev, addr, size, dir, attrs);
 	else
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	trace_dma_unmap_phys(dev, addr, size, dir, attrs);
diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
index 9afd569eadb9..6f9d604d9d40 100644
--- a/kernel/dma/ops_helpers.c
+++ b/kernel/dma/ops_helpers.c
@@ -72,8 +72,8 @@ struct page *dma_common_alloc_pages(struct device *dev, size_t size,
 		return NULL;
 
 	if (use_dma_iommu(dev))
-		*dma_handle = iommu_dma_map_page(dev, page, 0, size, dir,
-						 DMA_ATTR_SKIP_CPU_SYNC);
+		*dma_handle = iommu_dma_map_phys(dev, page_to_phys(page), size,
+						 dir, DMA_ATTR_SKIP_CPU_SYNC);
 	else
 		*dma_handle = ops->map_page(dev, page, 0, size, dir,
 					    DMA_ATTR_SKIP_CPU_SYNC);
@@ -92,7 +92,7 @@ void dma_common_free_pages(struct device *dev, size_t size, struct page *page,
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 
 	if (use_dma_iommu(dev))
-		iommu_dma_unmap_page(dev, dma_handle, size, dir,
+		iommu_dma_unmap_phys(dev, dma_handle, size, dir,
 				     DMA_ATTR_SKIP_CPU_SYNC);
 	else if (ops->unmap_page)
 		ops->unmap_page(dev, dma_handle, size, dir,
-- 
2.50.1

[PATCH v2 06/16] iommu/dma: extend iommu_dma_*map_phys API to handle MMIO memory

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Combine iommu_dma_*map_phys with iommu_dma_*map_resource interfaces in
order to allow single phys_addr_t flow.

In the following patches, the iommu_dma_map_resource() will be removed
in favour of iommu_dma_map_phys(..., attrs | DMA_ATTR_MMIO) flow.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/iommu/dma-iommu.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index aea119f32f96..6804aaf034a1 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1211,16 +1211,19 @@ dma_addr_t iommu_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
 	 */
 	if (dev_use_swiotlb(dev, size, dir) &&
 	    iova_unaligned(iovad, phys, size)) {
+		if (attrs & DMA_ATTR_MMIO)
+			return DMA_MAPPING_ERROR;
+
 		phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
 		if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
 			return DMA_MAPPING_ERROR;
 	}
 
-	if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+	if (!coherent && !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO)))
 		arch_sync_dma_for_device(phys, size, dir);
 
 	iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
-	if (iova == DMA_MAPPING_ERROR)
+	if (iova == DMA_MAPPING_ERROR && !(attrs & DMA_ATTR_MMIO))
 		swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
 	return iova;
 }
@@ -1228,10 +1231,14 @@ dma_addr_t iommu_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
 void iommu_dma_unmap_phys(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;
 
-	phys = iommu_iova_to_phys(domain, dma_handle);
+	if (attrs & DMA_ATTR_MMIO) {
+		__iommu_dma_unmap(dev, dma_handle, size);
+		return;
+	}
+
+	phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);
 	if (WARN_ON(!phys))
 		return;
 
-- 
2.50.1

[PATCH v2 07/16] dma-mapping: convert dma_direct_*map_page to be phys_addr_t based

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Convert the DMA direct mapping functions to accept physical addresses
directly instead of page+offset parameters. The functions were already
operating on physical addresses internally, so this change eliminates
the redundant page-to-physical conversion at the API boundary.

The functions dma_direct_map_page() and dma_direct_unmap_page() are
renamed to dma_direct_map_phys() and dma_direct_unmap_phys() respectively,
with their calling convention changed from (struct page *page,
unsigned long offset) to (phys_addr_t phys).

Architecture-specific functions arch_dma_map_page_direct() and
arch_dma_unmap_page_direct() are similarly renamed to
arch_dma_map_phys_direct() and arch_dma_unmap_phys_direct().

The is_pci_p2pdma_page() checks are replaced with DMA_ATTR_MMIO checks
to allow integration with dma_direct_map_resource and dma_direct_map_phys()
is extended to support MMIO path either.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 arch/powerpc/kernel/dma-iommu.c |  4 +--
 include/linux/dma-map-ops.h     |  8 ++---
 kernel/dma/direct.c             |  6 ++--
 kernel/dma/direct.h             | 52 +++++++++++++++++++++------------
 kernel/dma/mapping.c            |  8 ++---
 5 files changed, 46 insertions(+), 32 deletions(-)

diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c
index 4d64a5db50f3..0359ab72cd3b 100644
--- a/arch/powerpc/kernel/dma-iommu.c
+++ b/arch/powerpc/kernel/dma-iommu.c
@@ -14,7 +14,7 @@
 #define can_map_direct(dev, addr) \
 	((dev)->bus_dma_limit >= phys_to_dma((dev), (addr)))
 
-bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr)
+bool arch_dma_map_phys_direct(struct device *dev, phys_addr_t addr)
 {
 	if (likely(!dev->bus_dma_limit))
 		return false;
@@ -24,7 +24,7 @@ bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr)
 
 #define is_direct_handle(dev, h) ((h) >= (dev)->archdata.dma_offset)
 
-bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle)
+bool arch_dma_unmap_phys_direct(struct device *dev, dma_addr_t dma_handle)
 {
 	if (likely(!dev->bus_dma_limit))
 		return false;
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index f48e5fb88bd5..71f5b3025415 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -392,15 +392,15 @@ void *arch_dma_set_uncached(void *addr, size_t size);
 void arch_dma_clear_uncached(void *addr, size_t size);
 
 #ifdef CONFIG_ARCH_HAS_DMA_MAP_DIRECT
-bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr);
-bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle);
+bool arch_dma_map_phys_direct(struct device *dev, phys_addr_t addr);
+bool arch_dma_unmap_phys_direct(struct device *dev, dma_addr_t dma_handle);
 bool arch_dma_map_sg_direct(struct device *dev, struct scatterlist *sg,
 		int nents);
 bool arch_dma_unmap_sg_direct(struct device *dev, struct scatterlist *sg,
 		int nents);
 #else
-#define arch_dma_map_page_direct(d, a)		(false)
-#define arch_dma_unmap_page_direct(d, a)	(false)
+#define arch_dma_map_phys_direct(d, a)		(false)
+#define arch_dma_unmap_phys_direct(d, a)	(false)
 #define arch_dma_map_sg_direct(d, s, n)		(false)
 #define arch_dma_unmap_sg_direct(d, s, n)	(false)
 #endif
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 24c359d9c879..fa75e3070073 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -453,7 +453,7 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
 		if (sg_dma_is_bus_address(sg))
 			sg_dma_unmark_bus_address(sg);
 		else
-			dma_direct_unmap_page(dev, sg->dma_address,
+			dma_direct_unmap_phys(dev, sg->dma_address,
 					      sg_dma_len(sg), dir, attrs);
 	}
 }
@@ -476,8 +476,8 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 			 */
 			break;
 		case PCI_P2PDMA_MAP_NONE:
-			sg->dma_address = dma_direct_map_page(dev, sg_page(sg),
-					sg->offset, sg->length, dir, attrs);
+			sg->dma_address = dma_direct_map_phys(dev, sg_phys(sg),
+					sg->length, dir, attrs);
 			if (sg->dma_address == DMA_MAPPING_ERROR) {
 				ret = -EIO;
 				goto out_unmap;
diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index d2c0b7e632fc..92dbadcd3b2f 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -80,42 +80,56 @@ static inline void dma_direct_sync_single_for_cpu(struct device *dev,
 		arch_dma_mark_clean(paddr, size);
 }
 
-static inline dma_addr_t dma_direct_map_page(struct device *dev,
-		struct page *page, unsigned long offset, size_t size,
-		enum dma_data_direction dir, unsigned long attrs)
+static inline dma_addr_t dma_direct_map_phys(struct device *dev,
+		phys_addr_t phys, size_t size, enum dma_data_direction dir,
+		unsigned long attrs)
 {
-	phys_addr_t phys = page_to_phys(page) + offset;
-	dma_addr_t dma_addr = phys_to_dma(dev, phys);
+	dma_addr_t dma_addr;
+	bool capable;
 
 	if (is_swiotlb_force_bounce(dev)) {
-		if (is_pci_p2pdma_page(page))
-			return DMA_MAPPING_ERROR;
+		if (attrs & DMA_ATTR_MMIO)
+			goto err_overflow;
+
 		return swiotlb_map(dev, phys, size, dir, attrs);
 	}
 
-	if (unlikely(!dma_capable(dev, dma_addr, size, true)) ||
-	    dma_kmalloc_needs_bounce(dev, size, dir)) {
-		if (is_pci_p2pdma_page(page))
-			return DMA_MAPPING_ERROR;
-		if (is_swiotlb_active(dev))
+	if (attrs & DMA_ATTR_MMIO)
+		dma_addr = phys;
+	else
+		dma_addr = phys_to_dma(dev, phys);
+
+	capable = dma_capable(dev, dma_addr, size, !(attrs & DMA_ATTR_MMIO));
+	if (unlikely(!capable) || dma_kmalloc_needs_bounce(dev, size, dir)) {
+		if (is_swiotlb_active(dev) && !(attrs & DMA_ATTR_MMIO))
 			return swiotlb_map(dev, phys, size, dir, attrs);
 
-		dev_WARN_ONCE(dev, 1,
-			     "DMA addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
-			     &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
-		return DMA_MAPPING_ERROR;
+		goto err_overflow;
 	}
 
-	if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+	if (!dev_is_dma_coherent(dev) &&
+	    !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO)))
 		arch_sync_dma_for_device(phys, size, dir);
 	return dma_addr;
+
+err_overflow:
+	dev_WARN_ONCE(
+		dev, 1,
+		"DMA addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
+		&dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
+	return DMA_MAPPING_ERROR;
 }
 
-static inline void dma_direct_unmap_page(struct device *dev, dma_addr_t addr,
+static inline void dma_direct_unmap_phys(struct device *dev, dma_addr_t addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-	phys_addr_t phys = dma_to_phys(dev, addr);
+	phys_addr_t phys;
+
+	if (attrs & DMA_ATTR_MMIO)
+		/* nothing to do: uncached and no swiotlb */
+		return;
 
+	phys = dma_to_phys(dev, addr);
 	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
 		dma_direct_sync_single_for_cpu(dev, addr, size, dir);
 
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 58482536db9b..80481a873340 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -166,8 +166,8 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		return DMA_MAPPING_ERROR;
 
 	if (dma_map_direct(dev, ops) ||
-	    arch_dma_map_page_direct(dev, phys + size))
-		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
+	    arch_dma_map_phys_direct(dev, phys + size))
+		addr = dma_direct_map_phys(dev, phys, size, dir, attrs);
 	else if (use_dma_iommu(dev))
 		addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
 	else
@@ -187,8 +187,8 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 
 	BUG_ON(!valid_dma_direction(dir));
 	if (dma_map_direct(dev, ops) ||
-	    arch_dma_unmap_page_direct(dev, addr + size))
-		dma_direct_unmap_page(dev, addr, size, dir, attrs);
+	    arch_dma_unmap_phys_direct(dev, addr + size))
+		dma_direct_unmap_phys(dev, addr, size, dir, attrs);
 	else if (use_dma_iommu(dev))
 		iommu_dma_unmap_phys(dev, addr, size, dir, attrs);
 	else
-- 
2.50.1

[PATCH v2 08/16] kmsan: convert kmsan_handle_dma to use physical addresses

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Convert the KMSAN DMA handling function from page-based to physical
address-based interface.

The refactoring renames kmsan_handle_dma() parameters from accepting
(struct page *page, size_t offset, size_t size) to (phys_addr_t phys,
size_t size). A PFN_VALID check is added to prevent KMSAN operations
on non-page memory, preventing from non struct page backed address,

As part of this change, support for highmem addresses is implemented
using kmap_local_page() to handle both lowmem and highmem regions
properly. All callers throughout the codebase are updated to use the
new phys_addr_t based interface.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/virtio/virtio_ring.c |  4 ++--
 include/linux/kmsan.h        | 12 +++++++-----
 kernel/dma/mapping.c         |  2 +-
 mm/kmsan/hooks.c             | 36 +++++++++++++++++++++++++++++-------
 tools/virtio/linux/kmsan.h   |  2 +-
 5 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index f5062061c408..c147145a6593 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -378,7 +378,7 @@ static int vring_map_one_sg(const struct vring_virtqueue *vq, struct scatterlist
 		 * is initialized by the hardware. Explicitly check/unpoison it
 		 * depending on the direction.
 		 */
-		kmsan_handle_dma(sg_page(sg), sg->offset, sg->length, direction);
+		kmsan_handle_dma(sg_phys(sg), sg->length, direction);
 		*addr = (dma_addr_t)sg_phys(sg);
 		return 0;
 	}
@@ -3157,7 +3157,7 @@ dma_addr_t virtqueue_dma_map_single_attrs(struct virtqueue *_vq, void *ptr,
 	struct vring_virtqueue *vq = to_vvq(_vq);
 
 	if (!vq->use_dma_api) {
-		kmsan_handle_dma(virt_to_page(ptr), offset_in_page(ptr), size, dir);
+		kmsan_handle_dma(virt_to_phys(ptr), size, dir);
 		return (dma_addr_t)virt_to_phys(ptr);
 	}
 
diff --git a/include/linux/kmsan.h b/include/linux/kmsan.h
index 2b1432cc16d5..6f27b9824ef7 100644
--- a/include/linux/kmsan.h
+++ b/include/linux/kmsan.h
@@ -182,8 +182,7 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
 
 /**
  * kmsan_handle_dma() - Handle a DMA data transfer.
- * @page:   first page of the buffer.
- * @offset: offset of the buffer within the first page.
+ * @phys:   physical address of the buffer.
  * @size:   buffer size.
  * @dir:    one of possible dma_data_direction values.
  *
@@ -191,8 +190,11 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end);
  * * checks the buffer, if it is copied to device;
  * * initializes the buffer, if it is copied from device;
  * * does both, if this is a DMA_BIDIRECTIONAL transfer.
+ *
+ * The function handles page lookup internally and supports both lowmem
+ * and highmem addresses.
  */
-void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+void kmsan_handle_dma(phys_addr_t phys, size_t size,
 		      enum dma_data_direction dir);
 
 /**
@@ -372,8 +374,8 @@ static inline void kmsan_iounmap_page_range(unsigned long start,
 {
 }
 
-static inline void kmsan_handle_dma(struct page *page, size_t offset,
-				    size_t size, enum dma_data_direction dir)
+static inline void kmsan_handle_dma(phys_addr_t phys, size_t size,
+				    enum dma_data_direction dir)
 {
 }
 
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 80481a873340..709405d46b2b 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -172,7 +172,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
 	else
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
-	kmsan_handle_dma(page, offset, size, dir);
+	kmsan_handle_dma(phys, size, dir);
 	trace_dma_map_phys(dev, phys, addr, size, dir, attrs);
 	debug_dma_map_phys(dev, phys, size, dir, addr, attrs);
 
diff --git a/mm/kmsan/hooks.c b/mm/kmsan/hooks.c
index 97de3d6194f0..eab7912a3bf0 100644
--- a/mm/kmsan/hooks.c
+++ b/mm/kmsan/hooks.c
@@ -336,25 +336,48 @@ static void kmsan_handle_dma_page(const void *addr, size_t size,
 }
 
 /* Helper function to handle DMA data transfers. */
-void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+void kmsan_handle_dma(phys_addr_t phys, size_t size,
 		      enum dma_data_direction dir)
 {
 	u64 page_offset, to_go, addr;
+	struct page *page;
+	void *kaddr;
 
-	if (PageHighMem(page))
+	if (!pfn_valid(PHYS_PFN(phys)))
 		return;
-	addr = (u64)page_address(page) + offset;
+
+	page = phys_to_page(phys);
+	page_offset = offset_in_page(phys);
+
 	/*
 	 * The kernel may occasionally give us adjacent DMA pages not belonging
 	 * to the same allocation. Process them separately to avoid triggering
 	 * internal KMSAN checks.
 	 */
 	while (size > 0) {
-		page_offset = offset_in_page(addr);
 		to_go = min(PAGE_SIZE - page_offset, (u64)size);
+
+		if (PageHighMem(page))
+			/* Handle highmem pages using kmap */
+			kaddr = kmap_local_page(page);
+		else
+			/* Lowmem pages can be accessed directly */
+			kaddr = page_address(page);
+
+		addr = (u64)kaddr + page_offset;
 		kmsan_handle_dma_page((void *)addr, to_go, dir);
-		addr += to_go;
+
+		if (PageHighMem(page))
+			kunmap_local(page);
+
+		phys += to_go;
 		size -= to_go;
+
+		/* Move to next page if needed */
+		if (size > 0) {
+			page = phys_to_page(phys);
+			page_offset = offset_in_page(phys);
+		}
 	}
 }
 EXPORT_SYMBOL_GPL(kmsan_handle_dma);
@@ -366,8 +389,7 @@ void kmsan_handle_dma_sg(struct scatterlist *sg, int nents,
 	int i;
 
 	for_each_sg(sg, item, nents, i)
-		kmsan_handle_dma(sg_page(item), item->offset, item->length,
-				 dir);
+		kmsan_handle_dma(sg_phys(item), item->length, dir);
 }
 
 /* Functions from kmsan-checks.h follow. */
diff --git a/tools/virtio/linux/kmsan.h b/tools/virtio/linux/kmsan.h
index 272b5aa285d5..6cd2e3efd03d 100644
--- a/tools/virtio/linux/kmsan.h
+++ b/tools/virtio/linux/kmsan.h
@@ -4,7 +4,7 @@
 
 #include <linux/gfp.h>
 
-inline void kmsan_handle_dma(struct page *page, size_t offset, size_t size,
+inline void kmsan_handle_dma(phys_addr_t phys, size_t size,
 			     enum dma_data_direction dir)
 {
 }
-- 
2.50.1

[PATCH v2 09/16] dma-mapping: handle MMIO flow in dma_map|unmap_page

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Extend base DMA page API to handle MMIO flow and follow
existing dma_map_resource() implementation to rely on dma_map_direct()
only to take DMA direct path.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 kernel/dma/mapping.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 709405d46b2b..8725508a6c57 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -158,6 +158,7 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
 	phys_addr_t phys = page_to_phys(page) + offset;
+	bool is_mmio = attrs & DMA_ATTR_MMIO;
 	dma_addr_t addr;
 
 	BUG_ON(!valid_dma_direction(dir));
@@ -166,12 +167,23 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		return DMA_MAPPING_ERROR;
 
 	if (dma_map_direct(dev, ops) ||
-	    arch_dma_map_phys_direct(dev, phys + size))
+	    (!is_mmio && arch_dma_map_phys_direct(dev, phys + size)))
 		addr = dma_direct_map_phys(dev, phys, size, dir, attrs);
 	else if (use_dma_iommu(dev))
 		addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
-	else
+	else if (is_mmio) {
+		if (!ops->map_resource)
+			return DMA_MAPPING_ERROR;
+
+		addr = ops->map_resource(dev, phys, size, dir, attrs);
+	} else {
+		/*
+		 * The dma_ops API contract for ops->map_page() requires
+		 * kmappable memory, while ops->map_resource() does not.
+		 */
 		addr = ops->map_page(dev, page, offset, size, dir, attrs);
+	}
+
 	kmsan_handle_dma(phys, size, dir);
 	trace_dma_map_phys(dev, phys, addr, size, dir, attrs);
 	debug_dma_map_phys(dev, phys, size, dir, addr, attrs);
@@ -184,14 +196,18 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
+	bool is_mmio = attrs & DMA_ATTR_MMIO;
 
 	BUG_ON(!valid_dma_direction(dir));
 	if (dma_map_direct(dev, ops) ||
-	    arch_dma_unmap_phys_direct(dev, addr + size))
+	    (!is_mmio && arch_dma_unmap_phys_direct(dev, addr + size)))
 		dma_direct_unmap_phys(dev, addr, size, dir, attrs);
 	else if (use_dma_iommu(dev))
 		iommu_dma_unmap_phys(dev, addr, size, dir, attrs);
-	else
+	else if (is_mmio) {
+		if (ops->unmap_resource)
+			ops->unmap_resource(dev, addr, size, dir, attrs);
+	} else
 		ops->unmap_page(dev, addr, size, dir, attrs);
 	trace_dma_unmap_phys(dev, addr, size, dir, attrs);
 	debug_dma_unmap_phys(dev, addr, size, dir);
-- 
2.50.1

[PATCH v2 10/16] xen: swiotlb: Open code map_resource callback

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

General dma_direct_map_resource() is going to be removed
in next patch, so simply open-code it in xen driver.

Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/xen/swiotlb-xen.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index da1a7d3d377c..dd7747a2de87 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -392,6 +392,25 @@ xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
 	}
 }
 
+static dma_addr_t xen_swiotlb_direct_map_resource(struct device *dev,
+						  phys_addr_t paddr,
+						  size_t size,
+						  enum dma_data_direction dir,
+						  unsigned long attrs)
+{
+	dma_addr_t dma_addr = paddr;
+
+	if (unlikely(!dma_capable(dev, dma_addr, size, false))) {
+		dev_err_once(dev,
+			     "DMA addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
+			     &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
+		WARN_ON_ONCE(1);
+		return DMA_MAPPING_ERROR;
+	}
+
+	return dma_addr;
+}
+
 /*
  * Return whether the given device DMA address mask can be supported
  * properly.  For example, if your device can only drive the low 24-bits
@@ -426,5 +445,5 @@ const struct dma_map_ops xen_swiotlb_dma_ops = {
 	.alloc_pages_op = dma_common_alloc_pages,
 	.free_pages = dma_common_free_pages,
 	.max_mapping_size = swiotlb_max_mapping_size,
-	.map_resource = dma_direct_map_resource,
+	.map_resource = xen_swiotlb_direct_map_resource,
 };
-- 
2.50.1

[PATCH v2 11/16] dma-mapping: export new dma_*map_phys() interface

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Introduce new DMA mapping functions dma_map_phys() and dma_unmap_phys()
that operate directly on physical addresses instead of page+offset
parameters. This provides a more efficient interface for drivers that
already have physical addresses available.

The new functions are implemented as the primary mapping layer, with
the existing dma_map_page_attrs()/dma_map_resource() and
dma_unmap_page_attrs()/dma_unmap_resource() functions converted to simple
wrappers around the phys-based implementations.

In case dma_map_page_attrs(), the struct page is converted to physical
address with help of page_to_phys() function and dma_map_resource()
provides physical address as is together with addition of DMA_ATTR_MMIO
attribute.

The old page-based API is preserved in mapping.c to ensure that existing
code won't be affected by changing EXPORT_SYMBOL to EXPORT_SYMBOL_GPL
variant for dma_*map_phys().

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/iommu/dma-iommu.c   | 14 --------
 include/linux/dma-direct.h  |  2 --
 include/linux/dma-mapping.h | 13 +++++++
 include/linux/iommu-dma.h   |  4 ---
 include/trace/events/dma.h  |  2 --
 kernel/dma/debug.c          | 43 -----------------------
 kernel/dma/debug.h          | 21 -----------
 kernel/dma/direct.c         | 16 ---------
 kernel/dma/mapping.c        | 69 ++++++++++++++++++++-----------------
 9 files changed, 50 insertions(+), 134 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 6804aaf034a1..7944a3af4545 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1556,20 +1556,6 @@ void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
 		__iommu_dma_unmap(dev, start, end - start);
 }
 
-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));
-}
-
-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);
-}
-
 static void __iommu_dma_free(struct device *dev, size_t size, void *cpu_addr)
 {
 	size_t alloc_size = PAGE_ALIGN(size);
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index f3bc0bcd7098..c249912456f9 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -149,7 +149,5 @@ void dma_direct_free_pages(struct device *dev, size_t size,
 		struct page *page, dma_addr_t dma_addr,
 		enum dma_data_direction dir);
 int dma_direct_supported(struct device *dev, u64 mask);
-dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
-		size_t size, enum dma_data_direction dir, unsigned long attrs);
 
 #endif /* _LINUX_DMA_DIRECT_H */
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index ead5514d389e..cebfbe237595 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -138,6 +138,10 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 		unsigned long attrs);
 void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 		enum dma_data_direction dir, unsigned long attrs);
+dma_addr_t dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
+		enum dma_data_direction dir, unsigned long attrs);
+void dma_unmap_phys(struct device *dev, dma_addr_t addr, size_t size,
+		enum dma_data_direction dir, unsigned long attrs);
 unsigned int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
 		int nents, enum dma_data_direction dir, unsigned long attrs);
 void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg,
@@ -192,6 +196,15 @@ static inline void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
 }
+static inline dma_addr_t dma_map_phys(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 dma_unmap_phys(struct device *dev, dma_addr_t addr,
+		size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+}
 static inline unsigned int dma_map_sg_attrs(struct device *dev,
 		struct scatterlist *sg, int nents, enum dma_data_direction dir,
 		unsigned long attrs)
diff --git a/include/linux/iommu-dma.h b/include/linux/iommu-dma.h
index 485bdffed988..a92b3ff9b934 100644
--- a/include/linux/iommu-dma.h
+++ b/include/linux/iommu-dma.h
@@ -42,10 +42,6 @@ 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,
diff --git a/include/trace/events/dma.h b/include/trace/events/dma.h
index 84416c7d6bfa..5da59fd8121d 100644
--- a/include/trace/events/dma.h
+++ b/include/trace/events/dma.h
@@ -73,7 +73,6 @@ DEFINE_EVENT(dma_map, name, \
 	TP_ARGS(dev, phys_addr, dma_addr, size, dir, attrs))
 
 DEFINE_MAP_EVENT(dma_map_phys);
-DEFINE_MAP_EVENT(dma_map_resource);
 
 DECLARE_EVENT_CLASS(dma_unmap,
 	TP_PROTO(struct device *dev, dma_addr_t addr, size_t size,
@@ -111,7 +110,6 @@ DEFINE_EVENT(dma_unmap, name, \
 	TP_ARGS(dev, addr, size, dir, attrs))
 
 DEFINE_UNMAP_EVENT(dma_unmap_phys);
-DEFINE_UNMAP_EVENT(dma_unmap_resource);
 
 DECLARE_EVENT_CLASS(dma_alloc_class,
 	TP_PROTO(struct device *dev, void *virt_addr, dma_addr_t dma_addr,
diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index da6734e3a4ce..06e31fd216e3 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -38,7 +38,6 @@ enum {
 	dma_debug_single,
 	dma_debug_sg,
 	dma_debug_coherent,
-	dma_debug_resource,
 	dma_debug_phy,
 };
 
@@ -141,7 +140,6 @@ static const char *type2name[] = {
 	[dma_debug_single] = "single",
 	[dma_debug_sg] = "scatter-gather",
 	[dma_debug_coherent] = "coherent",
-	[dma_debug_resource] = "resource",
 	[dma_debug_phy] = "phy",
 };
 
@@ -1448,47 +1446,6 @@ void debug_dma_free_coherent(struct device *dev, size_t size,
 	check_unmap(&ref);
 }
 
-void debug_dma_map_resource(struct device *dev, phys_addr_t addr, size_t size,
-			    int direction, dma_addr_t dma_addr,
-			    unsigned long attrs)
-{
-	struct dma_debug_entry *entry;
-
-	if (unlikely(dma_debug_disabled()))
-		return;
-
-	entry = dma_entry_alloc();
-	if (!entry)
-		return;
-
-	entry->type		= dma_debug_resource;
-	entry->dev		= dev;
-	entry->paddr		= addr;
-	entry->size		= size;
-	entry->dev_addr		= dma_addr;
-	entry->direction	= direction;
-	entry->map_err_type	= MAP_ERR_NOT_CHECKED;
-
-	add_dma_entry(entry, attrs);
-}
-
-void debug_dma_unmap_resource(struct device *dev, dma_addr_t dma_addr,
-			      size_t size, int direction)
-{
-	struct dma_debug_entry ref = {
-		.type           = dma_debug_resource,
-		.dev            = dev,
-		.dev_addr       = dma_addr,
-		.size           = size,
-		.direction      = direction,
-	};
-
-	if (unlikely(dma_debug_disabled()))
-		return;
-
-	check_unmap(&ref);
-}
-
 void debug_dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
 				   size_t size, int direction)
 {
diff --git a/kernel/dma/debug.h b/kernel/dma/debug.h
index 76adb42bffd5..424b8f912ade 100644
--- a/kernel/dma/debug.h
+++ b/kernel/dma/debug.h
@@ -30,14 +30,6 @@ extern void debug_dma_alloc_coherent(struct device *dev, size_t size,
 extern void debug_dma_free_coherent(struct device *dev, size_t size,
 				    void *virt, dma_addr_t addr);
 
-extern void debug_dma_map_resource(struct device *dev, phys_addr_t addr,
-				   size_t size, int direction,
-				   dma_addr_t dma_addr,
-				   unsigned long attrs);
-
-extern void debug_dma_unmap_resource(struct device *dev, dma_addr_t dma_addr,
-				     size_t size, int direction);
-
 extern void debug_dma_sync_single_for_cpu(struct device *dev,
 					  dma_addr_t dma_handle, size_t size,
 					  int direction);
@@ -88,19 +80,6 @@ static inline void debug_dma_free_coherent(struct device *dev, size_t size,
 {
 }
 
-static inline void debug_dma_map_resource(struct device *dev, phys_addr_t addr,
-					  size_t size, int direction,
-					  dma_addr_t dma_addr,
-					  unsigned long attrs)
-{
-}
-
-static inline void debug_dma_unmap_resource(struct device *dev,
-					    dma_addr_t dma_addr, size_t size,
-					    int direction)
-{
-}
-
 static inline void debug_dma_sync_single_for_cpu(struct device *dev,
 						 dma_addr_t dma_handle,
 						 size_t size, int direction)
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index fa75e3070073..1062caac47e7 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -502,22 +502,6 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 	return ret;
 }
 
-dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
-		size_t size, enum dma_data_direction dir, unsigned long attrs)
-{
-	dma_addr_t dma_addr = paddr;
-
-	if (unlikely(!dma_capable(dev, dma_addr, size, false))) {
-		dev_err_once(dev,
-			     "DMA addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
-			     &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
-		WARN_ON_ONCE(1);
-		return DMA_MAPPING_ERROR;
-	}
-
-	return dma_addr;
-}
-
 int dma_direct_get_sgtable(struct device *dev, struct sg_table *sgt,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		unsigned long attrs)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 8725508a6c57..7e0e21a7ba04 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -152,12 +152,10 @@ static inline bool dma_map_direct(struct device *dev,
 	return dma_go_direct(dev, *dev->dma_mask, ops);
 }
 
-dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
-		size_t offset, size_t size, enum dma_data_direction dir,
-		unsigned long attrs)
+dma_addr_t dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
+		enum dma_data_direction dir, unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
-	phys_addr_t phys = page_to_phys(page) + offset;
 	bool is_mmio = attrs & DMA_ATTR_MMIO;
 	dma_addr_t addr;
 
@@ -177,6 +175,9 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 
 		addr = ops->map_resource(dev, phys, size, dir, attrs);
 	} else {
+		struct page *page = phys_to_page(phys);
+		size_t offset = offset_in_page(phys);
+
 		/*
 		 * The dma_ops API contract for ops->map_page() requires
 		 * kmappable memory, while ops->map_resource() does not.
@@ -190,9 +191,26 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
 
 	return addr;
 }
+EXPORT_SYMBOL_GPL(dma_map_phys);
+
+dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page,
+		size_t offset, size_t size, enum dma_data_direction dir,
+		unsigned long attrs)
+{
+	phys_addr_t phys = page_to_phys(page) + offset;
+
+	if (unlikely(attrs & DMA_ATTR_MMIO))
+		return DMA_MAPPING_ERROR;
+
+	if (IS_ENABLED(CONFIG_DMA_API_DEBUG) &&
+	    WARN_ON_ONCE(is_zone_device_page(page)))
+		return DMA_MAPPING_ERROR;
+
+	return dma_map_phys(dev, phys, size, dir, attrs);
+}
 EXPORT_SYMBOL(dma_map_page_attrs);
 
-void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
+void dma_unmap_phys(struct device *dev, dma_addr_t addr, size_t size,
 		enum dma_data_direction dir, unsigned long attrs)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
@@ -212,6 +230,16 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
 	trace_dma_unmap_phys(dev, addr, size, dir, attrs);
 	debug_dma_unmap_phys(dev, addr, size, dir);
 }
+EXPORT_SYMBOL_GPL(dma_unmap_phys);
+
+void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size,
+		 enum dma_data_direction dir, unsigned long attrs)
+{
+	if (unlikely(attrs & DMA_ATTR_MMIO))
+		return;
+
+	dma_unmap_phys(dev, addr, size, dir, attrs);
+}
 EXPORT_SYMBOL(dma_unmap_page_attrs);
 
 static int __dma_map_sg_attrs(struct device *dev, struct scatterlist *sg,
@@ -337,41 +365,18 @@ EXPORT_SYMBOL(dma_unmap_sg_attrs);
 dma_addr_t dma_map_resource(struct device *dev, phys_addr_t phys_addr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
-	const struct dma_map_ops *ops = get_dma_ops(dev);
-	dma_addr_t addr = DMA_MAPPING_ERROR;
-
-	BUG_ON(!valid_dma_direction(dir));
-
-	if (WARN_ON_ONCE(!dev->dma_mask))
+	if (IS_ENABLED(CONFIG_DMA_API_DEBUG) &&
+	    WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr))))
 		return DMA_MAPPING_ERROR;
 
-	if (dma_map_direct(dev, ops))
-		addr = dma_direct_map_resource(dev, phys_addr, size, dir, attrs);
-	else if (use_dma_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);
-
-	trace_dma_map_resource(dev, phys_addr, addr, size, dir, attrs);
-	debug_dma_map_resource(dev, phys_addr, size, dir, addr, attrs);
-	return addr;
+	return dma_map_phys(dev, phys_addr, size, dir, attrs | DMA_ATTR_MMIO);
 }
 EXPORT_SYMBOL(dma_map_resource);
 
 void dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
 		enum dma_data_direction dir, unsigned long attrs)
 {
-	const struct dma_map_ops *ops = get_dma_ops(dev);
-
-	BUG_ON(!valid_dma_direction(dir));
-	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);
-	trace_dma_unmap_resource(dev, addr, size, dir, attrs);
-	debug_dma_unmap_resource(dev, addr, size, dir);
+	dma_unmap_phys(dev, addr, size, dir, attrs | DMA_ATTR_MMIO);
 }
 EXPORT_SYMBOL(dma_unmap_resource);
 
-- 
2.50.1

[PATCH v2 12/16] mm/hmm: migrate to physical address-based DMA mapping API

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Convert HMM DMA operations from the legacy page-based API to the new
physical address-based dma_map_phys() and dma_unmap_phys() functions.
This demonstrates the preferred approach for new code that should use
physical addresses directly rather than page+offset parameters.

The change replaces dma_map_page() and dma_unmap_page() calls with
dma_map_phys() and dma_unmap_phys() respectively, using the physical
address that was already available in the code. This eliminates the
redundant page-to-physical address conversion and aligns with the
DMA subsystem's move toward physical address-centric interfaces.

This serves as an example of how new code should be written to leverage
the more efficient physical address API, which provides cleaner interfaces
for drivers that already have access to physical addresses.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 mm/hmm.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index d545e2494994..015ab243f081 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -775,8 +775,8 @@ dma_addr_t hmm_dma_map_pfn(struct device *dev, struct hmm_dma_map *map,
 		if (WARN_ON_ONCE(dma_need_unmap(dev) && !dma_addrs))
 			goto error;
 
-		dma_addr = dma_map_page(dev, page, 0, map->dma_entry_size,
-					DMA_BIDIRECTIONAL);
+		dma_addr = dma_map_phys(dev, paddr, map->dma_entry_size,
+					DMA_BIDIRECTIONAL, 0);
 		if (dma_mapping_error(dev, dma_addr))
 			goto error;
 
@@ -819,8 +819,8 @@ bool hmm_dma_unmap_pfn(struct device *dev, struct hmm_dma_map *map, size_t idx)
 		dma_iova_unlink(dev, state, idx * map->dma_entry_size,
 				map->dma_entry_size, DMA_BIDIRECTIONAL, attrs);
 	} else if (dma_need_unmap(dev))
-		dma_unmap_page(dev, dma_addrs[idx], map->dma_entry_size,
-			       DMA_BIDIRECTIONAL);
+		dma_unmap_phys(dev, dma_addrs[idx], map->dma_entry_size,
+			       DMA_BIDIRECTIONAL, 0);
 
 	pfns[idx] &=
 		~(HMM_PFN_DMA_MAPPED | HMM_PFN_P2PDMA | HMM_PFN_P2PDMA_BUS);
-- 
2.50.1

[PATCH v2 13/16] mm/hmm: properly take MMIO path

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

In case peer-to-peer transaction traverses through host bridge,
the IOMMU needs to have IOMMU_MMIO flag, together with skip of
CPU sync.

The latter was handled by provided DMA_ATTR_SKIP_CPU_SYNC flag,
but IOMMU flag was missed, due to assumption that such memory
can be treated as regular one.

Reuse newly introduced DMA attribute to properly take MMIO path.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 mm/hmm.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 015ab243f081..6556c0e074ba 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -746,7 +746,7 @@ dma_addr_t hmm_dma_map_pfn(struct device *dev, struct hmm_dma_map *map,
 	case PCI_P2PDMA_MAP_NONE:
 		break;
 	case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
-		attrs |= DMA_ATTR_SKIP_CPU_SYNC;
+		attrs |= DMA_ATTR_MMIO;
 		pfns[idx] |= HMM_PFN_P2PDMA;
 		break;
 	case PCI_P2PDMA_MAP_BUS_ADDR:
@@ -776,7 +776,7 @@ dma_addr_t hmm_dma_map_pfn(struct device *dev, struct hmm_dma_map *map,
 			goto error;
 
 		dma_addr = dma_map_phys(dev, paddr, map->dma_entry_size,
-					DMA_BIDIRECTIONAL, 0);
+					DMA_BIDIRECTIONAL, attrs);
 		if (dma_mapping_error(dev, dma_addr))
 			goto error;
 
@@ -811,16 +811,17 @@ bool hmm_dma_unmap_pfn(struct device *dev, struct hmm_dma_map *map, size_t idx)
 	if ((pfns[idx] & valid_dma) != valid_dma)
 		return false;
 
+	if (pfns[idx] & HMM_PFN_P2PDMA)
+		attrs |= DMA_ATTR_MMIO;
+
 	if (pfns[idx] & HMM_PFN_P2PDMA_BUS)
 		; /* no need to unmap bus address P2P mappings */
-	else if (dma_use_iova(state)) {
-		if (pfns[idx] & HMM_PFN_P2PDMA)
-			attrs |= DMA_ATTR_SKIP_CPU_SYNC;
+	else if (dma_use_iova(state))
 		dma_iova_unlink(dev, state, idx * map->dma_entry_size,
 				map->dma_entry_size, DMA_BIDIRECTIONAL, attrs);
-	} else if (dma_need_unmap(dev))
+	else if (dma_need_unmap(dev))
 		dma_unmap_phys(dev, dma_addrs[idx], map->dma_entry_size,
-			       DMA_BIDIRECTIONAL, 0);
+			       DMA_BIDIRECTIONAL, attrs);
 
 	pfns[idx] &=
 		~(HMM_PFN_DMA_MAPPED | HMM_PFN_P2PDMA | HMM_PFN_P2PDMA_BUS);
-- 
2.50.1

[PATCH v2 14/16] block-dma: migrate to dma_map_phys instead of map_page

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

After introduction of dma_map_phys(), there is no need to convert
from physical address to struct page in order to map page. So let's
use it directly.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 block/blk-mq-dma.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index ad283017caef..37e2142be4f7 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -87,8 +87,8 @@ static bool blk_dma_map_bus(struct blk_dma_iter *iter, struct phys_vec *vec)
 static bool blk_dma_map_direct(struct request *req, struct device *dma_dev,
 		struct blk_dma_iter *iter, struct phys_vec *vec)
 {
-	iter->addr = dma_map_page(dma_dev, phys_to_page(vec->paddr),
-			offset_in_page(vec->paddr), vec->len, rq_dma_dir(req));
+	iter->addr = dma_map_phys(dma_dev, vec->paddr, vec->len,
+			rq_dma_dir(req), 0);
 	if (dma_mapping_error(dma_dev, iter->addr)) {
 		iter->status = BLK_STS_RESOURCE;
 		return false;
-- 
2.50.1

[PATCH v2 15/16] block-dma: properly take MMIO path

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Make sure that CPU is not synced and IOMMU is configured to take
MMIO path by providing newly introduced DMA_ATTR_MMIO attribute.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 block/blk-mq-dma.c         | 13 +++++++++++--
 include/linux/blk-mq-dma.h |  6 +++++-
 include/linux/blk_types.h  |  2 ++
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/block/blk-mq-dma.c b/block/blk-mq-dma.c
index 37e2142be4f7..d415088ed9fd 100644
--- a/block/blk-mq-dma.c
+++ b/block/blk-mq-dma.c
@@ -87,8 +87,13 @@ static bool blk_dma_map_bus(struct blk_dma_iter *iter, struct phys_vec *vec)
 static bool blk_dma_map_direct(struct request *req, struct device *dma_dev,
 		struct blk_dma_iter *iter, struct phys_vec *vec)
 {
+	unsigned int attrs = 0;
+
+	if (req->cmd_flags & REQ_MMIO)
+		attrs = DMA_ATTR_MMIO;
+
 	iter->addr = dma_map_phys(dma_dev, vec->paddr, vec->len,
-			rq_dma_dir(req), 0);
+			rq_dma_dir(req), attrs);
 	if (dma_mapping_error(dma_dev, iter->addr)) {
 		iter->status = BLK_STS_RESOURCE;
 		return false;
@@ -103,14 +108,17 @@ static bool blk_rq_dma_map_iova(struct request *req, struct device *dma_dev,
 {
 	enum dma_data_direction dir = rq_dma_dir(req);
 	unsigned int mapped = 0;
+	unsigned int attrs = 0;
 	int error;
 
 	iter->addr = state->addr;
 	iter->len = dma_iova_size(state);
+	if (req->cmd_flags & REQ_MMIO)
+		attrs = DMA_ATTR_MMIO;
 
 	do {
 		error = dma_iova_link(dma_dev, state, vec->paddr, mapped,
-				vec->len, dir, 0);
+				vec->len, dir, attrs);
 		if (error)
 			break;
 		mapped += vec->len;
@@ -176,6 +184,7 @@ bool blk_rq_dma_map_iter_start(struct request *req, struct device *dma_dev,
 			 * same as non-P2P transfers below and during unmap.
 			 */
 			req->cmd_flags &= ~REQ_P2PDMA;
+			req->cmd_flags |= REQ_MMIO;
 			break;
 		default:
 			iter->status = BLK_STS_INVAL;
diff --git a/include/linux/blk-mq-dma.h b/include/linux/blk-mq-dma.h
index c26a01aeae00..6c55f5e58511 100644
--- a/include/linux/blk-mq-dma.h
+++ b/include/linux/blk-mq-dma.h
@@ -48,12 +48,16 @@ static inline bool blk_rq_dma_map_coalesce(struct dma_iova_state *state)
 static inline bool blk_rq_dma_unmap(struct request *req, struct device *dma_dev,
 		struct dma_iova_state *state, size_t mapped_len)
 {
+	unsigned int attrs = 0;
+
 	if (req->cmd_flags & REQ_P2PDMA)
 		return true;
 
 	if (dma_use_iova(state)) {
+		if (req->cmd_flags & REQ_MMIO)
+			attrs = DMA_ATTR_MMIO;
 		dma_iova_destroy(dma_dev, state, mapped_len, rq_dma_dir(req),
-				 0);
+				 attrs);
 		return true;
 	}
 
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 09b99d52fd36..283058bcb5b1 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -387,6 +387,7 @@ enum req_flag_bits {
 	__REQ_FS_PRIVATE,	/* for file system (submitter) use */
 	__REQ_ATOMIC,		/* for atomic write operations */
 	__REQ_P2PDMA,		/* contains P2P DMA pages */
+	__REQ_MMIO,		/* contains MMIO memory */
 	/*
 	 * Command specific flags, keep last:
 	 */
@@ -420,6 +421,7 @@ enum req_flag_bits {
 #define REQ_FS_PRIVATE	(__force blk_opf_t)(1ULL << __REQ_FS_PRIVATE)
 #define REQ_ATOMIC	(__force blk_opf_t)(1ULL << __REQ_ATOMIC)
 #define REQ_P2PDMA	(__force blk_opf_t)(1ULL << __REQ_P2PDMA)
+#define REQ_MMIO	(__force blk_opf_t)(1ULL << __REQ_MMIO)
 
 #define REQ_NOUNMAP	(__force blk_opf_t)(1ULL << __REQ_NOUNMAP)
 
-- 
2.50.1

[PATCH v2 16/16] nvme-pci: unmap MMIO pages with appropriate interface

[Leon Romanovsky]

From: Leon Romanovsky <leonro@nvidia.com>

Block layer maps MMIO memory through dma_map_phys() interface
with help of DMA_ATTR_MMIO attribute. There is a need to unmap
that memory with the appropriate unmap function, something which
wasn't possible before adding new REQ attribute to block layer in
previous patch.

Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
 drivers/nvme/host/pci.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 2c6d9506b172..f8ecc0e0f576 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -682,11 +682,15 @@ static void nvme_free_prps(struct request *req)
 {
 	struct nvme_iod *iod = blk_mq_rq_to_pdu(req);
 	struct nvme_queue *nvmeq = req->mq_hctx->driver_data;
+	unsigned int attrs = 0;
 	unsigned int i;
 
+	if (req->cmd_flags & REQ_MMIO)
+		attrs = DMA_ATTR_MMIO;
+
 	for (i = 0; i < iod->nr_dma_vecs; i++)
-		dma_unmap_page(nvmeq->dev->dev, iod->dma_vecs[i].addr,
-				iod->dma_vecs[i].len, rq_dma_dir(req));
+		dma_unmap_phys(nvmeq->dev->dev, iod->dma_vecs[i].addr,
+				iod->dma_vecs[i].len, rq_dma_dir(req), attrs);
 	mempool_free(iod->dma_vecs, nvmeq->dev->dmavec_mempool);
 }
 
@@ -699,15 +703,19 @@ static void nvme_free_sgls(struct request *req)
 	unsigned int sqe_dma_len = le32_to_cpu(iod->cmd.common.dptr.sgl.length);
 	struct nvme_sgl_desc *sg_list = iod->descriptors[0];
 	enum dma_data_direction dir = rq_dma_dir(req);
+	unsigned int attrs = 0;
+
+	if (req->cmd_flags & REQ_MMIO)
+		attrs = DMA_ATTR_MMIO;
 
 	if (iod->nr_descriptors) {
 		unsigned int nr_entries = sqe_dma_len / sizeof(*sg_list), i;
 
 		for (i = 0; i < nr_entries; i++)
-			dma_unmap_page(dma_dev, le64_to_cpu(sg_list[i].addr),
-				le32_to_cpu(sg_list[i].length), dir);
+			dma_unmap_phys(dma_dev, le64_to_cpu(sg_list[i].addr),
+				le32_to_cpu(sg_list[i].length), dir, attrs);
 	} else {
-		dma_unmap_page(dma_dev, sqe_dma_addr, sqe_dma_len, dir);
+		dma_unmap_phys(dma_dev, sqe_dma_addr, sqe_dma_len, dir, attrs);
 	}
 }
 
-- 
2.50.1

Re: [PATCH v2 01/16] dma-mapping: introduce new DMA attribute to indicate MMIO memory

[Randy Dunlap]

Hi Leon,

On 8/14/25 3:13 AM, Leon Romanovsky wrote:
> diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst
> index 1887d92e8e92..58a1528a9bb9 100644
> --- a/Documentation/core-api/dma-attributes.rst
> +++ b/Documentation/core-api/dma-attributes.rst
> @@ -130,3 +130,21 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged
>  subsystem that the buffer is fully accessible at the elevated privilege
>  level (and ideally inaccessible or at least read-only at the
>  lesser-privileged levels).
> +
> +DMA_ATTR_MMIO
> +-------------
> +
> +This attribute indicates the physical address is not normal system
> +memory. It may not be used with kmap*()/phys_to_virt()/phys_to_page()
> +functions, it may not be cachable, and access using CPU load/store

Usually "cacheable" (git grep -w cacheable counts 1042 hits vs.
55 hits for "cachable"). And the $internet agrees.

> +instructions may not be allowed.
> +
> +Usually this will be used to describe MMIO addresses, or other non

non-cacheable

> +cachable register addresses. When DMA mapping this sort of address we

> +call the operation Peer to Peer as a one device is DMA'ing to another
> +device. For PCI devices the p2pdma APIs must be used to determine if
> +DMA_ATTR_MMIO is appropriate.
> +
> +For architectures that require cache flushing for DMA coherence
> +DMA_ATTR_MMIO will not perform any cache flushing. The address
> +provided must never be mapped cachable into the CPU.
again.

thanks.
-- 
~Randy

Re: [PATCH v2 01/16] dma-mapping: introduce new DMA attribute to indicate MMIO memory

[Leon Romanovsky]

On Thu, Aug 14, 2025 at 10:37:22AM -0700, Randy Dunlap wrote:
> Hi Leon,
> 
> On 8/14/25 3:13 AM, Leon Romanovsky wrote:
> > diff --git a/Documentation/core-api/dma-attributes.rst b/Documentation/core-api/dma-attributes.rst
> > index 1887d92e8e92..58a1528a9bb9 100644
> > --- a/Documentation/core-api/dma-attributes.rst
> > +++ b/Documentation/core-api/dma-attributes.rst
> > @@ -130,3 +130,21 @@ accesses to DMA buffers in both privileged "supervisor" and unprivileged
> >  subsystem that the buffer is fully accessible at the elevated privilege
> >  level (and ideally inaccessible or at least read-only at the
> >  lesser-privileged levels).
> > +
> > +DMA_ATTR_MMIO
> > +-------------
> > +
> > +This attribute indicates the physical address is not normal system
> > +memory. It may not be used with kmap*()/phys_to_virt()/phys_to_page()
> > +functions, it may not be cachable, and access using CPU load/store
> 
> Usually "cacheable" (git grep -w cacheable counts 1042 hits vs.
> 55 hits for "cachable"). And the $internet agrees.
> 
> > +instructions may not be allowed.
> > +
> > +Usually this will be used to describe MMIO addresses, or other non
> 
> non-cacheable
> 
> > +cachable register addresses. When DMA mapping this sort of address we
> 
> > +call the operation Peer to Peer as a one device is DMA'ing to another
> > +device. For PCI devices the p2pdma APIs must be used to determine if
> > +DMA_ATTR_MMIO is appropriate.
> > +
> > +For architectures that require cache flushing for DMA coherence
> > +DMA_ATTR_MMIO will not perform any cache flushing. The address
> > +provided must never be mapped cachable into the CPU.
> again.

Thanks, I will fix.

> 
> thanks.
> -- 
> ~Randy
> 
>