[PATCH v3 0/5] dma-mapping: arm64: support batched cache sync

[PATCH v3 0/5] dma-mapping: arm64: support batched cache sync

[Barry Song]

From: Barry Song <baohua@kernel.org>

Many embedded ARM64 SoCs still lack hardware cache coherency support, which
causes DMA mapping operations to appear as hotspots in on-CPU flame graphs.

For an SG list with *nents* entries, the current dma_map/unmap_sg() and DMA
sync APIs perform cache maintenance one entry at a time. After each entry,
the implementation synchronously waits for the corresponding region’s
D-cache operations to complete. On architectures like arm64, efficiency can
be improved by issuing all entries’ operations first and then performing a
single batched wait for completion.

Tangquan's results show that batched synchronization can reduce
dma_map_sg() time by 64.61% and dma_unmap_sg() time by 66.60% on an MTK
phone platform (MediaTek Dimensity 9500). The tests were performed by
pinning the task to CPU7 and fixing the CPU frequency at 2.6 GHz,
running dma_map_sg() and dma_unmap_sg() on 10 MB buffers (10 MB / 4 KB
sg entries per buffer) for 200 iterations and then averaging the
results.

Thanks to Xueyuan for volunteering to take on the testing tasks. He
put significant effort into validating paths such as IOVA link/unlink
and SWIOTLB on RK3588 boards with NVMe.

v3:
 * Fold patches 5/8, 7/8, and 8/8 into patch 4/8 as suggested by Leon,
   reducing the series from 8 patches to 5;
 * Fix the SWIOTLB path by ensuring a sync is issued before memcpy;
 * Add ARCH_HAS_BATCHED_DMA_SYNC Kconfig as suggested by Leon;
 * Collect Reviewed-by tags from Leon and Juergen. Leon's tag is not
   added to patch 4 since it has changed significantly since v2 and
   requires re-review;
 * Rename some asm macros and functions as suggested by Will;
 * Add Xueyuan's Tested-by. His help is greatly appreciated!
 v2 link:
 https://lore.kernel.org/lkml/20251226225254.46197-1-21cnbao@gmail.com/

v2:
 * Refine a large amount of arm64 asm code based on feedback from
   Robin, thanks!
 * Drop batch_add APIs and always use arch_sync_dma_for_* + flush,
   even for a single buffer, based on Leon’s suggestion, thanks!
 * Refine a large amount of code based on feedback from Leon, thanks!
 * Also add batch support for iommu_dma_sync_sg_for_{cpu,device}
v1 link:
 https://lore.kernel.org/lkml/20251219053658.84978-1-21cnbao@gmail.com/

v1, diff with RFC:
 * Drop a large number of #ifdef/#else/#endif blocks based on feedback
   from Catalin and Marek, thanks!
 * Also add batched iova link/unlink support, marked as RFC since I lack
   the required hardware. This was suggested by Marek, thanks!
RFC link:
 https://lore.kernel.org/lkml/20251029023115.22809-1-21cnbao@gmail.com/

Barry Song (5):
  arm64: Provide dcache_by_myline_op_nosync helper
  arm64: Provide dcache_clean_poc_nosync helper
  arm64: Provide dcache_inval_poc_nosync helper
  dma-mapping: Separate DMA sync issuing and completion waiting
  dma-mapping: Support batch mode for dma_direct_{map,unmap}_sg

 arch/arm64/Kconfig                  |  1 +
 arch/arm64/include/asm/assembler.h  | 25 ++++++++++---
 arch/arm64/include/asm/cache.h      |  5 +++
 arch/arm64/include/asm/cacheflush.h |  2 +
 arch/arm64/kernel/relocate_kernel.S |  3 +-
 arch/arm64/mm/cache.S               | 57 +++++++++++++++++++++++------
 arch/arm64/mm/dma-mapping.c         |  4 +-
 drivers/iommu/dma-iommu.c           | 35 ++++++++++++++----
 drivers/xen/swiotlb-xen.c           | 24 ++++++++----
 include/linux/dma-map-ops.h         |  6 +++
 kernel/dma/Kconfig                  |  3 ++
 kernel/dma/direct.c                 | 23 +++++++++---
 kernel/dma/direct.h                 | 21 ++++++++---
 kernel/dma/mapping.c                |  6 +--
 kernel/dma/swiotlb.c                |  7 +++-
 15 files changed, 171 insertions(+), 51 deletions(-)

Cc: Leon Romanovsky <leon@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Cc: Tangquan Zheng <zhengtangquan@oppo.com>
Cc: Huacai Zhou <zhouhuacai@oppo.com>
Cc: Xueyuan Chen <xueyuan.chen21@gmail.com>
-- 
2.39.3 (Apple Git-146)

[PATCH v3 1/5] arm64: Provide dcache_by_myline_op_nosync helper

[Barry Song]

From: Barry Song <baohua@kernel.org>

dcache_by_myline_op ensures completion of the data cache operations for a
region, while dcache_by_myline_op_nosync only issues them without waiting.
This enables deferred synchronization so completion for multiple regions
can be handled together later.

Cc: Leon Romanovsky <leon@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tangquan Zheng <zhengtangquan@oppo.com>
Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
Signed-off-by: Barry Song <baohua@kernel.org>
---
 arch/arm64/include/asm/assembler.h  | 25 +++++++++++++++++++------
 arch/arm64/kernel/relocate_kernel.S |  3 ++-
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index d3d46e5f7188..cdbaad41bddb 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -371,14 +371,13 @@ alternative_endif
  * [start, end) with dcache line size explicitly provided.
  *
  * 	op:		operation passed to dc instruction
- * 	domain:		domain used in dsb instruction
  * 	start:          starting virtual address of the region
  * 	end:            end virtual address of the region
  *	linesz:		dcache line size
  * 	fixup:		optional label to branch to on user fault
  * 	Corrupts:       start, end, tmp
  */
-	.macro dcache_by_myline_op op, domain, start, end, linesz, tmp, fixup
+	.macro dcache_by_myline_op_nosync op, start, end, linesz, tmp, fixup
 	sub	\tmp, \linesz, #1
 	bic	\start, \start, \tmp
 alternative_if ARM64_WORKAROUND_4311569
@@ -412,14 +411,28 @@ alternative_if ARM64_WORKAROUND_4311569
 	cbnz	\start, .Ldcache_op\@
 	.endif
 alternative_else_nop_endif
-	dsb	\domain
 
 	_cond_uaccess_extable .Ldcache_op\@, \fixup
 	.endm
 
 /*
  * Macro to perform a data cache maintenance for the interval
- * [start, end)
+ * [start, end) without waiting for completion
+ *
+ * 	op:		operation passed to dc instruction
+ * 	start:          starting virtual address of the region
+ * 	end:            end virtual address of the region
+ * 	fixup:		optional label to branch to on user fault
+ * 	Corrupts:       start, end, tmp1, tmp2
+ */
+	.macro dcache_by_line_op_nosync op, start, end, tmp1, tmp2, fixup
+	dcache_line_size \tmp1, \tmp2
+	dcache_by_myline_op_nosync \op, \start, \end, \tmp1, \tmp2, \fixup
+	.endm
+
+/*
+ * Macro to perform a data cache maintenance for the interval
+ * [start, end) and wait for completion
  *
  * 	op:		operation passed to dc instruction
  * 	domain:		domain used in dsb instruction
@@ -429,8 +442,8 @@ alternative_else_nop_endif
  * 	Corrupts:       start, end, tmp1, tmp2
  */
 	.macro dcache_by_line_op op, domain, start, end, tmp1, tmp2, fixup
-	dcache_line_size \tmp1, \tmp2
-	dcache_by_myline_op \op, \domain, \start, \end, \tmp1, \tmp2, \fixup
+	dcache_by_line_op_nosync \op, \start, \end, \tmp1, \tmp2, \fixup
+	dsb \domain
 	.endm
 
 /*
diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index 413f899e4ac6..6cb4209f5dab 100644
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -64,7 +64,8 @@ SYM_CODE_START(arm64_relocate_new_kernel)
 	mov	x19, x13
 	copy_page x13, x12, x1, x2, x3, x4, x5, x6, x7, x8
 	add	x1, x19, #PAGE_SIZE
-	dcache_by_myline_op civac, sy, x19, x1, x15, x20
+	dcache_by_myline_op_nosync civac, x19, x1, x15, x20
+	dsb	sy
 	b	.Lnext
 .Ltest_indirection:
 	tbz	x16, IND_INDIRECTION_BIT, .Ltest_destination
-- 
2.39.3 (Apple Git-146)

Re: [PATCH v3 1/5] arm64: Provide dcache_by_myline_op_nosync helper

[Catalin Marinas]

On Sun, Mar 01, 2026 at 06:12:16AM +0800, Barry Song wrote:
> From: Barry Song <baohua@kernel.org>
> 
> dcache_by_myline_op ensures completion of the data cache operations for a
> region, while dcache_by_myline_op_nosync only issues them without waiting.
> This enables deferred synchronization so completion for multiple regions
> can be handled together later.
> 
> Cc: Leon Romanovsky <leon@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Tangquan Zheng <zhengtangquan@oppo.com>
> Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
> Signed-off-by: Barry Song <baohua@kernel.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

[PATCH v3 2/5] arm64: Provide dcache_clean_poc_nosync helper

[Barry Song]

From: Barry Song <baohua@kernel.org>

dcache_clean_poc_nosync does not wait for the data cache clean to
complete. Later, we wait for completion of all scatter-gather entries
together.

Cc: Leon Romanovsky <leon@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tangquan Zheng <zhengtangquan@oppo.com>
Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
Signed-off-by: Barry Song <baohua@kernel.org>
---
 arch/arm64/include/asm/cacheflush.h |  1 +
 arch/arm64/mm/cache.S               | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index 28ab96e808ef..9b6d0a62cf3d 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -74,6 +74,7 @@ extern void icache_inval_pou(unsigned long start, unsigned long end);
 extern void dcache_clean_inval_poc(unsigned long start, unsigned long end);
 extern void dcache_inval_poc(unsigned long start, unsigned long end);
 extern void dcache_clean_poc(unsigned long start, unsigned long end);
+extern void dcache_clean_poc_nosync(unsigned long start, unsigned long end);
 extern void dcache_clean_pop(unsigned long start, unsigned long end);
 extern void dcache_clean_pou(unsigned long start, unsigned long end);
 extern long caches_clean_inval_user_pou(unsigned long start, unsigned long end);
diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
index 503567c864fd..4a7c7e03785d 100644
--- a/arch/arm64/mm/cache.S
+++ b/arch/arm64/mm/cache.S
@@ -178,6 +178,21 @@ SYM_FUNC_START(__pi_dcache_clean_poc)
 SYM_FUNC_END(__pi_dcache_clean_poc)
 SYM_FUNC_ALIAS(dcache_clean_poc, __pi_dcache_clean_poc)
 
+/*
+ *	dcache_clean_poc_nosync(start, end)
+ *
+ * 	Issue the instructions of D-cache lines for the interval [start, end).
+ * 	not necessarily cleaned to the PoC till an explicit dsb sy afterward.
+ *
+ *	- start   - virtual start address of region
+ *	- end     - virtual end address of region
+ */
+SYM_FUNC_START(__pi_dcache_clean_poc_nosync)
+	dcache_by_line_op_nosync cvac, x0, x1, x2, x3
+	ret
+SYM_FUNC_END(__pi_dcache_clean_poc_nosync)
+SYM_FUNC_ALIAS(dcache_clean_poc_nosync, __pi_dcache_clean_poc_nosync)
+
 /*
  *	dcache_clean_pop(start, end)
  *
-- 
2.39.3 (Apple Git-146)

Re: [PATCH v3 2/5] arm64: Provide dcache_clean_poc_nosync helper

[Catalin Marinas]

On Sun, Mar 01, 2026 at 06:12:39AM +0800, Barry Song wrote:
> From: Barry Song <baohua@kernel.org>
> 
> dcache_clean_poc_nosync does not wait for the data cache clean to
> complete. Later, we wait for completion of all scatter-gather entries
> together.
> 
> Cc: Leon Romanovsky <leon@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Tangquan Zheng <zhengtangquan@oppo.com>
> Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
> Signed-off-by: Barry Song <baohua@kernel.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

[PATCH v3 3/5] arm64: Provide dcache_inval_poc_nosync helper

[Barry Song]

From: Barry Song <baohua@kernel.org>

dcache_inval_poc_nosync does not wait for the data cache invalidation to
complete. Later, we defer the synchronization so we can wait for all SG
entries together.

Cc: Leon Romanovsky <leon@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Tangquan Zheng <zhengtangquan@oppo.com>
Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
Signed-off-by: Barry Song <baohua@kernel.org>
---
 arch/arm64/include/asm/cacheflush.h |  1 +
 arch/arm64/mm/cache.S               | 42 +++++++++++++++++++++--------
 2 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index 9b6d0a62cf3d..382b4ac3734d 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -74,6 +74,7 @@ extern void icache_inval_pou(unsigned long start, unsigned long end);
 extern void dcache_clean_inval_poc(unsigned long start, unsigned long end);
 extern void dcache_inval_poc(unsigned long start, unsigned long end);
 extern void dcache_clean_poc(unsigned long start, unsigned long end);
+extern void dcache_inval_poc_nosync(unsigned long start, unsigned long end);
 extern void dcache_clean_poc_nosync(unsigned long start, unsigned long end);
 extern void dcache_clean_pop(unsigned long start, unsigned long end);
 extern void dcache_clean_pou(unsigned long start, unsigned long end);
diff --git a/arch/arm64/mm/cache.S b/arch/arm64/mm/cache.S
index 4a7c7e03785d..ab75c050f559 100644
--- a/arch/arm64/mm/cache.S
+++ b/arch/arm64/mm/cache.S
@@ -132,17 +132,7 @@ alternative_else_nop_endif
 	ret
 SYM_FUNC_END(dcache_clean_pou)
 
-/*
- *	dcache_inval_poc(start, end)
- *
- * 	Ensure that any D-cache lines for the interval [start, end)
- * 	are invalidated. Any partial lines at the ends of the interval are
- *	also cleaned to PoC to prevent data loss.
- *
- *	- start   - kernel start address of region
- *	- end     - kernel end address of region
- */
-SYM_FUNC_START(__pi_dcache_inval_poc)
+.macro __dcache_inval_poc_nosync
 	dcache_line_size x2, x3
 	sub	x3, x2, #1
 	tst	x1, x3				// end cache line aligned?
@@ -158,11 +148,41 @@ SYM_FUNC_START(__pi_dcache_inval_poc)
 3:	add	x0, x0, x2
 	cmp	x0, x1
 	b.lo	2b
+.endm
+
+/*
+ *	dcache_inval_poc(start, end)
+ *
+ * 	Ensure that any D-cache lines for the interval [start, end)
+ * 	are invalidated. Any partial lines at the ends of the interval are
+ *	also cleaned to PoC to prevent data loss.
+ *
+ *	- start   - kernel start address of region
+ *	- end     - kernel end address of region
+ */
+SYM_FUNC_START(__pi_dcache_inval_poc)
+	__dcache_inval_poc_nosync
 	dsb	sy
 	ret
 SYM_FUNC_END(__pi_dcache_inval_poc)
 SYM_FUNC_ALIAS(dcache_inval_poc, __pi_dcache_inval_poc)
 
+/*
+ *	dcache_inval_poc_nosync(start, end)
+ *
+ * 	Issue the instructions of D-cache lines for the interval [start, end)
+ * 	for invalidation. Not necessarily cleaned to PoC till an explicit dsb
+ *	sy is issued later
+ *
+ *	- start   - kernel start address of region
+ *	- end     - kernel end address of region
+ */
+SYM_FUNC_START(__pi_dcache_inval_poc_nosync)
+	__dcache_inval_poc_nosync
+	ret
+SYM_FUNC_END(__pi_dcache_inval_poc_nosync)
+SYM_FUNC_ALIAS(dcache_inval_poc_nosync, __pi_dcache_inval_poc_nosync)
+
 /*
  *	dcache_clean_poc(start, end)
  *
-- 
2.39.3 (Apple Git-146)

Re: [PATCH v3 3/5] arm64: Provide dcache_inval_poc_nosync helper

[Catalin Marinas]

On Sun, Mar 01, 2026 at 06:12:58AM +0800, Barry Song wrote:
> From: Barry Song <baohua@kernel.org>
> 
> dcache_inval_poc_nosync does not wait for the data cache invalidation to
> complete. Later, we defer the synchronization so we can wait for all SG
> entries together.
> 
> Cc: Leon Romanovsky <leon@kernel.org>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Tangquan Zheng <zhengtangquan@oppo.com>
> Tested-by: Xueyuan Chen <xueyuan.chen21@gmail.com>
> Signed-off-by: Barry Song <baohua@kernel.org>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Re: [PATCH v3 0/5] dma-mapping: arm64: support batched cache sync

[Marek Szyprowski]

On 28.02.2026 23:11, Barry Song wrote:
> From: Barry Song <baohua@kernel.org>
>
> Many embedded ARM64 SoCs still lack hardware cache coherency support, which
> causes DMA mapping operations to appear as hotspots in on-CPU flame graphs.
>
> For an SG list with *nents* entries, the current dma_map/unmap_sg() and DMA
> sync APIs perform cache maintenance one entry at a time. After each entry,
> the implementation synchronously waits for the corresponding region’s
> D-cache operations to complete. On architectures like arm64, efficiency can
> be improved by issuing all entries’ operations first and then performing a
> single batched wait for completion.
>
> Tangquan's results show that batched synchronization can reduce
> dma_map_sg() time by 64.61% and dma_unmap_sg() time by 66.60% on an MTK
> phone platform (MediaTek Dimensity 9500). The tests were performed by
> pinning the task to CPU7 and fixing the CPU frequency at 2.6 GHz,
> running dma_map_sg() and dma_unmap_sg() on 10 MB buffers (10 MB / 4 KB
> sg entries per buffer) for 200 iterations and then averaging the
> results.
>
> Thanks to Xueyuan for volunteering to take on the testing tasks. He
> put significant effort into validating paths such as IOVA link/unlink
> and SWIOTLB on RK3588 boards with NVMe.

Catalin, Will, I would like to merge this to dma-mapping tree, give Your 
ack or comment if You are okay with ARM64 related parts.


> v3:
>   * Fold patches 5/8, 7/8, and 8/8 into patch 4/8 as suggested by Leon,
>     reducing the series from 8 patches to 5;
>   * Fix the SWIOTLB path by ensuring a sync is issued before memcpy;
>   * Add ARCH_HAS_BATCHED_DMA_SYNC Kconfig as suggested by Leon;
>   * Collect Reviewed-by tags from Leon and Juergen. Leon's tag is not
>     added to patch 4 since it has changed significantly since v2 and
>     requires re-review;
>   * Rename some asm macros and functions as suggested by Will;
>   * Add Xueyuan's Tested-by. His help is greatly appreciated!
>   v2 link:
>   https://lore.kernel.org/lkml/20251226225254.46197-1-21cnbao@gmail.com/
>
> v2:
>   * Refine a large amount of arm64 asm code based on feedback from
>     Robin, thanks!
>   * Drop batch_add APIs and always use arch_sync_dma_for_* + flush,
>     even for a single buffer, based on Leon’s suggestion, thanks!
>   * Refine a large amount of code based on feedback from Leon, thanks!
>   * Also add batch support for iommu_dma_sync_sg_for_{cpu,device}
> v1 link:
>   https://lore.kernel.org/lkml/20251219053658.84978-1-21cnbao@gmail.com/
>
> v1, diff with RFC:
>   * Drop a large number of #ifdef/#else/#endif blocks based on feedback
>     from Catalin and Marek, thanks!
>   * Also add batched iova link/unlink support, marked as RFC since I lack
>     the required hardware. This was suggested by Marek, thanks!
> RFC link:
>   https://lore.kernel.org/lkml/20251029023115.22809-1-21cnbao@gmail.com/
>
> Barry Song (5):
>    arm64: Provide dcache_by_myline_op_nosync helper
>    arm64: Provide dcache_clean_poc_nosync helper
>    arm64: Provide dcache_inval_poc_nosync helper
>    dma-mapping: Separate DMA sync issuing and completion waiting
>    dma-mapping: Support batch mode for dma_direct_{map,unmap}_sg
>
>   arch/arm64/Kconfig                  |  1 +
>   arch/arm64/include/asm/assembler.h  | 25 ++++++++++---
>   arch/arm64/include/asm/cache.h      |  5 +++
>   arch/arm64/include/asm/cacheflush.h |  2 +
>   arch/arm64/kernel/relocate_kernel.S |  3 +-
>   arch/arm64/mm/cache.S               | 57 +++++++++++++++++++++++------
>   arch/arm64/mm/dma-mapping.c         |  4 +-
>   drivers/iommu/dma-iommu.c           | 35 ++++++++++++++----
>   drivers/xen/swiotlb-xen.c           | 24 ++++++++----
>   include/linux/dma-map-ops.h         |  6 +++
>   kernel/dma/Kconfig                  |  3 ++
>   kernel/dma/direct.c                 | 23 +++++++++---
>   kernel/dma/direct.h                 | 21 ++++++++---
>   kernel/dma/mapping.c                |  6 +--
>   kernel/dma/swiotlb.c                |  7 +++-
>   15 files changed, 171 insertions(+), 51 deletions(-)
>
> Cc: Leon Romanovsky <leon@kernel.org>
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Marc Zyngier <maz@kernel.org>
> Cc: Anshuman Khandual <anshuman.khandual@arm.com>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: Suren Baghdasaryan <surenb@google.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Joerg Roedel <joro@8bytes.org>
> Cc: Juergen Gross <jgross@suse.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> Cc: Tangquan Zheng <zhengtangquan@oppo.com>
> Cc: Huacai Zhou <zhouhuacai@oppo.com>
> Cc: Xueyuan Chen <xueyuan.chen21@gmail.com>

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Re: [PATCH v3 0/5] dma-mapping: arm64: support batched cache sync

[Catalin Marinas]

On Tue, Mar 03, 2026 at 05:33:37PM +0100, Marek Szyprowski wrote:
> On 28.02.2026 23:11, Barry Song wrote:
> > From: Barry Song <baohua@kernel.org>
> >
> > Many embedded ARM64 SoCs still lack hardware cache coherency support, which
> > causes DMA mapping operations to appear as hotspots in on-CPU flame graphs.
> >
> > For an SG list with *nents* entries, the current dma_map/unmap_sg() and DMA
> > sync APIs perform cache maintenance one entry at a time. After each entry,
> > the implementation synchronously waits for the corresponding region’s
> > D-cache operations to complete. On architectures like arm64, efficiency can
> > be improved by issuing all entries’ operations first and then performing a
> > single batched wait for completion.
> >
> > Tangquan's results show that batched synchronization can reduce
> > dma_map_sg() time by 64.61% and dma_unmap_sg() time by 66.60% on an MTK
> > phone platform (MediaTek Dimensity 9500). The tests were performed by
> > pinning the task to CPU7 and fixing the CPU frequency at 2.6 GHz,
> > running dma_map_sg() and dma_unmap_sg() on 10 MB buffers (10 MB / 4 KB
> > sg entries per buffer) for 200 iterations and then averaging the
> > results.
> >
> > Thanks to Xueyuan for volunteering to take on the testing tasks. He
> > put significant effort into validating paths such as IOVA link/unlink
> > and SWIOTLB on RK3588 boards with NVMe.
> 
> Catalin, Will, I would like to merge this to dma-mapping tree, give Your 
> ack or comment if You are okay with ARM64 related parts.

Sorry for the delay. Yes, feel free to pick them up. I doubt there would
be any conflicts in this area with what I'm merging through the arm64
tree.

Thanks.

-- 
Catalin

Re: [PATCH v3 0/5] dma-mapping: arm64: support batched cache sync

[Marek Szyprowski]

On 13.03.2026 20:36, Catalin Marinas wrote:
> On Tue, Mar 03, 2026 at 05:33:37PM +0100, Marek Szyprowski wrote:
>> On 28.02.2026 23:11, Barry Song wrote:
>>> From: Barry Song <baohua@kernel.org>
>>>
>>> Many embedded ARM64 SoCs still lack hardware cache coherency support, which
>>> causes DMA mapping operations to appear as hotspots in on-CPU flame graphs.
>>>
>>> For an SG list with *nents* entries, the current dma_map/unmap_sg() and DMA
>>> sync APIs perform cache maintenance one entry at a time. After each entry,
>>> the implementation synchronously waits for the corresponding region’s
>>> D-cache operations to complete. On architectures like arm64, efficiency can
>>> be improved by issuing all entries’ operations first and then performing a
>>> single batched wait for completion.
>>>
>>> Tangquan's results show that batched synchronization can reduce
>>> dma_map_sg() time by 64.61% and dma_unmap_sg() time by 66.60% on an MTK
>>> phone platform (MediaTek Dimensity 9500). The tests were performed by
>>> pinning the task to CPU7 and fixing the CPU frequency at 2.6 GHz,
>>> running dma_map_sg() and dma_unmap_sg() on 10 MB buffers (10 MB / 4 KB
>>> sg entries per buffer) for 200 iterations and then averaging the
>>> results.
>>>
>>> Thanks to Xueyuan for volunteering to take on the testing tasks. He
>>> put significant effort into validating paths such as IOVA link/unlink
>>> and SWIOTLB on RK3588 boards with NVMe.
>> Catalin, Will, I would like to merge this to dma-mapping tree, give Your
>> ack or comment if You are okay with ARM64 related parts.
> Sorry for the delay. Yes, feel free to pick them up. I doubt there would
> be any conflicts in this area with what I'm merging through the arm64
> tree.

Thanks, applied to dma-mapping-for-next.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland