Re: [RFC] avoid indirect calls for DMA direct mappings
From: Robin Murphy
Date: Thu Dec 06 2018 - 15:24:45 EST
On 06/12/2018 20:00, Christoph Hellwig wrote:
On Thu, Dec 06, 2018 at 06:54:17PM +0000, Robin Murphy wrote:
I'm pretty sure we used to assign dummy_dma_ops explicitly to devices at
the point we detected the ACPI properties are wrong - that shouldn't be too
much of a headache to go back to.
Ok. I've cooked up a patch to use NULL as the go direct marker.
This cleans up a few things nicely, but also means we now need to
do the bypass scheme for all ops, not just the fast path. But we
probably should just move the slow path ops out of line anyway,
so I'm not worried about it. This has survived some very basic
testing on x86, and really needs to be cleaned up and split into
multiple patches..
I've also just finished hacking something up to keep the arm64 status
quo - I'll need to actually test it tomorrow, but the overall diff looks
like the below.
Robin.
----->8-----
diff --git a/arch/arm64/include/asm/dma-mapping.h
b/arch/arm64/include/asm/dma-mapping.h
index 0626c3a93730..fe6287f68adb 100644
--- a/arch/arm64/include/asm/dma-mapping.h
+++ b/arch/arm64/include/asm/dma-mapping.h
@@ -19,15 +19,13 @@
#include <linux/types.h>
#include <linux/vmalloc.h>
-extern const struct dma_map_ops dummy_dma_ops;
-
static inline const struct dma_map_ops *get_arch_dma_ops(struct
bus_type *bus)
{
/*
* We expect no ISA devices, and all other DMA masters are expected to
* have someone call arch_setup_dma_ops at device creation time.
*/
- return &dummy_dma_ops;
+ return &dma_dummy_ops;
}
void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 17f8fc784de2..574aee2d04e7 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -255,98 +255,6 @@ static int __init atomic_pool_init(void)
return -ENOMEM;
}
-/********************************************
- * The following APIs are for dummy DMA ops *
- ********************************************/
-
-static void *__dummy_alloc(struct device *dev, size_t size,
- dma_addr_t *dma_handle, gfp_t flags,
- unsigned long attrs)
-{
- return NULL;
-}
-
-static void __dummy_free(struct device *dev, size_t size,
- void *vaddr, dma_addr_t dma_handle,
- unsigned long attrs)
-{
-}
-
-static int __dummy_mmap(struct device *dev,
- struct vm_area_struct *vma,
- void *cpu_addr, dma_addr_t dma_addr, size_t size,
- unsigned long attrs)
-{
- return -ENXIO;
-}
-
-static dma_addr_t __dummy_map_page(struct device *dev, struct page *page,
- unsigned long offset, size_t size,
- enum dma_data_direction dir,
- unsigned long attrs)
-{
- return 0;
-}
-
-static void __dummy_unmap_page(struct device *dev, dma_addr_t dev_addr,
- size_t size, enum dma_data_direction dir,
- unsigned long attrs)
-{
-}
-
-static int __dummy_map_sg(struct device *dev, struct scatterlist *sgl,
- int nelems, enum dma_data_direction dir,
- unsigned long attrs)
-{
- return 0;
-}
-
-static void __dummy_unmap_sg(struct device *dev,
- struct scatterlist *sgl, int nelems,
- enum dma_data_direction dir,
- unsigned long attrs)
-{
-}
-
-static void __dummy_sync_single(struct device *dev,
- dma_addr_t dev_addr, size_t size,
- enum dma_data_direction dir)
-{
-}
-
-static void __dummy_sync_sg(struct device *dev,
- struct scatterlist *sgl, int nelems,
- enum dma_data_direction dir)
-{
-}
-
-static int __dummy_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
-{
- return 1;
-}
-
-static int __dummy_dma_supported(struct device *hwdev, u64 mask)
-{
- return 0;
-}
-
-const struct dma_map_ops dummy_dma_ops = {
- .alloc = __dummy_alloc,
- .free = __dummy_free,
- .mmap = __dummy_mmap,
- .map_page = __dummy_map_page,
- .unmap_page = __dummy_unmap_page,
- .map_sg = __dummy_map_sg,
- .unmap_sg = __dummy_unmap_sg,
- .sync_single_for_cpu = __dummy_sync_single,
- .sync_single_for_device = __dummy_sync_single,
- .sync_sg_for_cpu = __dummy_sync_sg,
- .sync_sg_for_device = __dummy_sync_sg,
- .mapping_error = __dummy_mapping_error,
- .dma_supported = __dummy_dma_supported,
-};
-EXPORT_SYMBOL(dummy_dma_ops);
-
static int __init arm64_dma_init(void)
{
WARN_TAINT(ARCH_DMA_MINALIGN < cache_line_size(),
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index bd1c59fb0e17..b75ae34ed188 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1456,6 +1456,11 @@ int acpi_dma_configure(struct device *dev, enum
dev_dma_attr attr)
const struct iommu_ops *iommu;
u64 dma_addr = 0, size = 0;
+ if (attr == DEV_DMA_NOT_SUPPORTED) {
+ set_dma_ops(dev, &dma_dummy_ops);
+ return 0;
+ }
+
iort_dma_setup(dev, &dma_addr, &size);
iommu = iort_iommu_configure(dev);
diff --git a/drivers/base/platform.c b/drivers/base/platform.c
index 41b91af95afb..c6daca875c17 100644
--- a/drivers/base/platform.c
+++ b/drivers/base/platform.c
@@ -1138,8 +1138,7 @@ int platform_dma_configure(struct device *dev)
ret = of_dma_configure(dev, dev->of_node, true);
} else if (has_acpi_companion(dev)) {
attr = acpi_get_dma_attr(to_acpi_device_node(dev->fwnode));
- if (attr != DEV_DMA_NOT_SUPPORTED)
- ret = acpi_dma_configure(dev, attr);
+ ret = acpi_dma_configure(dev, attr);
}
return ret;
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index bef17c3fca67..f899a28b90f8 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -1602,8 +1602,7 @@ static int pci_dma_configure(struct device *dev)
struct acpi_device *adev = to_acpi_device_node(bridge->fwnode);
enum dev_dma_attr attr = acpi_get_dma_attr(adev);
- if (attr != DEV_DMA_NOT_SUPPORTED)
- ret = acpi_dma_configure(dev, attr);
+ ret = acpi_dma_configure(dev, attr);
}
pci_put_host_bridge_device(bridge);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 15bd41447025..3a1928ea23c9 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -134,6 +134,7 @@ struct dma_map_ops {
};
extern const struct dma_map_ops dma_direct_ops;
+extern const struct dma_map_ops dma_dummy_ops;
extern const struct dma_map_ops dma_virt_ops;
#define DMA_BIT_MASK(n) (((n) == 64) ? ~0ULL : ((1ULL<<(n))-1))
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 58dec7a92b7b..957a42ebabcf 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -346,3 +346,57 @@ void dma_common_free_remap(void *cpu_addr, size_t
size, unsigned long vm_flags)
vunmap(cpu_addr);
}
#endif
+
+/*
+ * Dummy DMA ops always fail
+ */
+
+static int dma_dummy_mmap(struct device *dev, struct vm_area_struct *vma,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
+{
+ return -ENXIO;
+}
+
+static dma_addr_t dma_dummy_map_page(struct device *dev, struct page *page,
+ unsigned long offset, size_t size,
+ enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ return 0;
+}
+
+static int dma_dummy_map_sg(struct device *dev, struct scatterlist *sgl,
+ int nelems, enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ return 0;
+}
+
+static dma_addr_t dma_dummy_map_resource(struct device *dev,
+ phys_addr_t phys_addr, size_t size,
+ enum dma_data_direction dir,
+ unsigned long attrs)
+{
+ return 0;
+}
+
+static int dma_dummy_mapping_error(struct device *hwdev, dma_addr_t
dma_addr)
+{
+ return 1;
+}
+
+static int dma_dummy_supported(struct device *hwdev, u64 mask)
+{
+ return 0;
+}
+
+const struct dma_map_ops dma_dummy_ops = {
+ .mmap = dma_dummy_mmap,
+ .map_page = dma_dummy_map_page,
+ .map_sg = dma_dummy_map_sg,
+ .map_resource = dma_dummy_map_resource,
+ .mapping_error = dma_dummy_mapping_error,
+ .dma_supported = dma_dummy_supported,
+};
+EXPORT_SYMBOL(dma_dummy_ops);