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Message-ID: <20251226225254.46197-7-21cnbao@gmail.com>
Date: Sat, 27 Dec 2025 11:52:46 +1300
From: Barry Song <21cnbao@...il.com>
To: catalin.marinas@....com,
m.szyprowski@...sung.com,
robin.murphy@....com,
will@...nel.org,
iommu@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org
Cc: linux-kernel@...r.kernel.org,
xen-devel@...ts.xenproject.org,
Barry Song <baohua@...nel.org>,
Leon Romanovsky <leon@...nel.org>,
Ada Couprie Diaz <ada.coupriediaz@....com>,
Ard Biesheuvel <ardb@...nel.org>,
Marc Zyngier <maz@...nel.org>,
Anshuman Khandual <anshuman.khandual@....com>,
Ryan Roberts <ryan.roberts@....com>,
Suren Baghdasaryan <surenb@...gle.com>,
Tangquan Zheng <zhengtangquan@...o.com>
Subject: [PATCH v2 6/8] dma-mapping: Support batch mode for dma_direct_{map,unmap}_sg
From: Barry Song <baohua@...nel.org>
Leon suggested extending a flush argument to
dma_direct_unmap_phys(), dma_direct_map_phys(), and
dma_direct_sync_single_for_cpu(). For single-buffer cases, this
would use flush=true, while for SG cases flush=false would be
used, followed by a single flush after all cache operations are
issued in dma_direct_{map,unmap}_sg().
This ultimately benefits dma_map_sg() and dma_unmap_sg().
Cc: Leon Romanovsky <leon@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will@...nel.org>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Robin Murphy <robin.murphy@....com>
Cc: Ada Couprie Diaz <ada.coupriediaz@....com>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Anshuman Khandual <anshuman.khandual@....com>
Cc: Ryan Roberts <ryan.roberts@....com>
Cc: Suren Baghdasaryan <surenb@...gle.com>
Cc: Tangquan Zheng <zhengtangquan@...o.com>
Signed-off-by: Barry Song <baohua@...nel.org>
---
kernel/dma/direct.c | 17 +++++++++++++----
kernel/dma/direct.h | 16 ++++++++++------
kernel/dma/mapping.c | 6 +++---
3 files changed, 26 insertions(+), 13 deletions(-)
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 98bacf562ca1..550a1a13148d 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -447,14 +447,19 @@ void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
{
struct scatterlist *sg;
int i;
+ bool need_sync = false;
for_each_sg(sgl, sg, nents, i) {
- if (sg_dma_is_bus_address(sg))
+ if (sg_dma_is_bus_address(sg)) {
sg_dma_unmark_bus_address(sg);
- else
+ } else {
+ need_sync = true;
dma_direct_unmap_phys(dev, sg->dma_address,
- sg_dma_len(sg), dir, attrs);
+ sg_dma_len(sg), dir, attrs, false);
+ }
}
+ if (need_sync && !dev_is_dma_coherent(dev))
+ arch_sync_dma_flush();
}
#endif
@@ -464,6 +469,7 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
struct pci_p2pdma_map_state p2pdma_state = {};
struct scatterlist *sg;
int i, ret;
+ bool need_sync = false;
for_each_sg(sgl, sg, nents, i) {
switch (pci_p2pdma_state(&p2pdma_state, dev, sg_page(sg))) {
@@ -475,8 +481,9 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
*/
break;
case PCI_P2PDMA_MAP_NONE:
+ need_sync = true;
sg->dma_address = dma_direct_map_phys(dev, sg_phys(sg),
- sg->length, dir, attrs);
+ sg->length, dir, attrs, false);
if (sg->dma_address == DMA_MAPPING_ERROR) {
ret = -EIO;
goto out_unmap;
@@ -495,6 +502,8 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
sg_dma_len(sg) = sg->length;
}
+ if (need_sync && !dev_is_dma_coherent(dev))
+ arch_sync_dma_flush();
return nents;
out_unmap:
diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index a69326eed266..d4ad79828090 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -67,13 +67,15 @@ static inline void dma_direct_sync_single_for_device(struct device *dev,
}
static inline void dma_direct_sync_single_for_cpu(struct device *dev,
- dma_addr_t addr, size_t size, enum dma_data_direction dir)
+ dma_addr_t addr, size_t size, enum dma_data_direction dir,
+ bool flush)
{
phys_addr_t paddr = dma_to_phys(dev, addr);
if (!dev_is_dma_coherent(dev)) {
arch_sync_dma_for_cpu(paddr, size, dir);
- arch_sync_dma_flush();
+ if (flush)
+ arch_sync_dma_flush();
arch_sync_dma_for_cpu_all();
}
@@ -85,7 +87,7 @@ static inline void dma_direct_sync_single_for_cpu(struct device *dev,
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)
+ unsigned long attrs, bool flush)
{
dma_addr_t dma_addr;
@@ -114,7 +116,8 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev,
if (!dev_is_dma_coherent(dev) &&
!(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO))) {
arch_sync_dma_for_device(phys, size, dir);
- arch_sync_dma_flush();
+ if (flush)
+ arch_sync_dma_flush();
}
return dma_addr;
@@ -127,7 +130,8 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev,
}
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)
+ size_t size, enum dma_data_direction dir, unsigned long attrs,
+ bool flush)
{
phys_addr_t phys;
@@ -137,7 +141,7 @@ static inline void dma_direct_unmap_phys(struct device *dev, dma_addr_t addr,
phys = dma_to_phys(dev, addr);
if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
- dma_direct_sync_single_for_cpu(dev, addr, size, dir);
+ dma_direct_sync_single_for_cpu(dev, addr, size, dir, flush);
swiotlb_tbl_unmap_single(dev, phys, size, dir,
attrs | DMA_ATTR_SKIP_CPU_SYNC);
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 37163eb49f9f..d8cfa56a3cbb 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -166,7 +166,7 @@ dma_addr_t dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
if (dma_map_direct(dev, ops) ||
(!is_mmio && arch_dma_map_phys_direct(dev, phys + size)))
- addr = dma_direct_map_phys(dev, phys, size, dir, attrs);
+ addr = dma_direct_map_phys(dev, phys, size, dir, attrs, true);
else if (use_dma_iommu(dev))
addr = iommu_dma_map_phys(dev, phys, size, dir, attrs);
else if (ops->map_phys)
@@ -207,7 +207,7 @@ void dma_unmap_phys(struct device *dev, dma_addr_t addr, size_t size,
BUG_ON(!valid_dma_direction(dir));
if (dma_map_direct(dev, ops) ||
(!is_mmio && arch_dma_unmap_phys_direct(dev, addr + size)))
- dma_direct_unmap_phys(dev, addr, size, dir, attrs);
+ dma_direct_unmap_phys(dev, addr, size, dir, attrs, true);
else if (use_dma_iommu(dev))
iommu_dma_unmap_phys(dev, addr, size, dir, attrs);
else if (ops->unmap_phys)
@@ -373,7 +373,7 @@ void __dma_sync_single_for_cpu(struct device *dev, dma_addr_t addr, size_t size,
BUG_ON(!valid_dma_direction(dir));
if (dma_map_direct(dev, ops))
- dma_direct_sync_single_for_cpu(dev, addr, size, dir);
+ dma_direct_sync_single_for_cpu(dev, addr, size, dir, true);
else if (use_dma_iommu(dev))
iommu_dma_sync_single_for_cpu(dev, addr, size, dir);
else if (ops->sync_single_for_cpu)
--
2.43.0
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