On 4/8/21 10:01 AM, Logan Gunthorpe wrote:
Add a flags member to the dma_map_ops structure with one flag to
indicate support for PCI P2PDMA.
Also, add a helper to check if a device supports PCI P2PDMA.
Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
include/linux/dma-map-ops.h | 3 +++
include/linux/dma-mapping.h | 5 +++++
kernel/dma/mapping.c | 18 ++++++++++++++++++
3 files changed, 26 insertions(+)
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 51872e736e7b..481892822104 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -12,6 +12,9 @@
struct cma;
struct dma_map_ops {
+ unsigned int flags;
+#define DMA_F_PCI_P2PDMA_SUPPORTED (1 << 0)
+
Can we move this up and out of the struct member area, so that it looks
more like this:
/*
* Values for struct dma_map_ops.flags:
*
* DMA_F_PCI_P2PDMA_SUPPORTED: <documentation here...this is a good place to
* explain exactly what this flag is for.>
*/
#define DMA_F_PCI_P2PDMA_SUPPORTED (1 << 0)
struct dma_map_ops {
unsigned int flags;
void *(*alloc)(struct device *dev, size_t size,
dma_addr_t *dma_handle, gfp_t gfp,
unsigned long attrs);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 50b8f586cf59..c31980ecca62 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -146,6 +146,7 @@ int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
unsigned long attrs);
bool dma_can_mmap(struct device *dev);
int dma_supported(struct device *dev, u64 mask);
+bool dma_pci_p2pdma_supported(struct device *dev);
int dma_set_mask(struct device *dev, u64 mask);
int dma_set_coherent_mask(struct device *dev, u64 mask);
u64 dma_get_required_mask(struct device *dev);
@@ -247,6 +248,10 @@ static inline int dma_supported(struct device *dev, u64 mask)
{
return 0;
}
+static inline bool dma_pci_p2pdma_supported(struct device *dev)
+{
+ return 0;
Should be:
return false;
+}
static inline int dma_set_mask(struct device *dev, u64 mask)
{
return -EIO;
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 923089c4267b..ce44a0fcc4e5 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -573,6 +573,24 @@ int dma_supported(struct device *dev, u64 mask)
}
EXPORT_SYMBOL(dma_supported);
+bool dma_pci_p2pdma_supported(struct device *dev)
+{
+ const struct dma_map_ops *ops = get_dma_ops(dev);
+
+ /* if ops is not set, dma direct will be used which supports P2PDMA */
+ if (!ops)
+ return true;
+
+ /*
+ * Note: dma_ops_bypass is not checked here because P2PDMA should
+ * not be used with dma mapping ops that do not have support even
+ * if the specific device is bypassing them.
+ */
+
+ return ops->flags & DMA_F_PCI_P2PDMA_SUPPORTED;
Wow, rather unusual combination of things in order decide this. It feels
a bit over-complicated to have flags and ops and a bool function all
dealing with the same 1-bit answer, but there is no caller shown here,
so I'll have to come back to this after reviewing subsequent patches.
thanks,
--
John Hubbard
NVIDIA
+}
+EXPORT_SYMBOL_GPL(dma_pci_p2pdma_supported);
+
#ifdef CONFIG_ARCH_HAS_DMA_SET_MASK
void arch_dma_set_mask(struct device *dev, u64 mask);
#else
