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* fix default dma_mmap_* pgprot v3
@ 2019-08-07  6:16 Christoph Hellwig
  2019-08-07  6:16 ` [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_* Christoph Hellwig
  2019-08-07  6:16 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
  0 siblings, 2 replies; 5+ messages in thread
From: Christoph Hellwig @ 2019-08-07  6:16 UTC (permalink / raw)
  To: iommu
  Cc: Shawn Anastasio, Michael Ellerman, Russell King, Catalin Marinas,
	Will Deacon, Robin Murphy, Paul Burton, James Hogan,
	linuxppc-dev, linux-mips, linux-arm-kernel, linux-kernel

Hi all,

As Shawn pointed out we've had issues with the dma mmap pgprots ever
since the dma_common_mmap helper was added beyong the initial
architectures - we default to uncached mappings, but for devices that
are DMA coherent, or if the DMA_ATTR_NON_CONSISTENT is set (and
supported) this can lead to aliasing of cache attributes.  This patch
fixes that.  My explanation of why this hasn't been much of an issue
is that the dma_mmap_ helpers aren't used widely and mostly just in
architecture specific drivers.

Changes since v2:
 - fix m68knommu compile by inlining dma_prprot helper and providing
   a stub for !CONFIG_MMU
 - fix various typos in the commit messages

Changes since v1:
 - fix handling of DMA_ATTR_NON_CONSISTENT where it is a no-op
   (which is most architectures)
 - remove DMA_ATTR_WRITE_COMBINE on mips, as it seem dangerous as-is

^ permalink raw reply	[flat|nested] 5+ messages in thread

* [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_*
  2019-08-07  6:16 fix default dma_mmap_* pgprot v3 Christoph Hellwig
@ 2019-08-07  6:16 ` Christoph Hellwig
  2019-08-07  6:16 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
  1 sibling, 0 replies; 5+ messages in thread
From: Christoph Hellwig @ 2019-08-07  6:16 UTC (permalink / raw)
  To: iommu
  Cc: Shawn Anastasio, Michael Ellerman, Russell King, Catalin Marinas,
	Will Deacon, Robin Murphy, Paul Burton, James Hogan,
	linuxppc-dev, linux-mips, linux-arm-kernel, linux-kernel,
	Gavin Li

All the way back to introducing dma_common_mmap we've defaulted to mark
the pages as uncached.  But this is wrong for DMA coherent devices.
Later on DMA_ATTR_WRITE_COMBINE also got incorrect treatment as that
flag is only treated special on the alloc side for non-coherent devices.

Introduce a new dma_pgprot helper that deals with the check for coherent
devices so that only the remapping cases ever reach arch_dma_mmap_pgprot
and we thus ensure no aliasing of page attributes happens, which makes
the powerpc version of arch_dma_mmap_pgprot obsolete and simplifies the
remaining ones.

Note that this means arch_dma_mmap_pgprot is a bit misnamed now, but
we'll phase it out soon.

Fixes: 64ccc9c033c6 ("common: dma-mapping: add support for generic dma_mmap_* calls")
Reported-by: Shawn Anastasio <shawn@anastas.io>
Reported-by: Gavin Li <git@thegavinli.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com> # arm64
---
 arch/arm/mm/dma-mapping.c        |  4 +---
 arch/arm64/mm/dma-mapping.c      |  4 +---
 arch/powerpc/Kconfig             |  1 -
 arch/powerpc/kernel/dma-common.c | 17 -----------------
 drivers/iommu/dma-iommu.c        |  6 +++---
 include/linux/dma-noncoherent.h  | 13 +++++++++----
 kernel/dma/mapping.c             | 17 ++++++++++++++++-
 kernel/dma/remap.c               |  2 +-
 8 files changed, 31 insertions(+), 33 deletions(-)
 delete mode 100644 arch/powerpc/kernel/dma-common.c

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 6774b03aa405..d42557ee69c2 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -2405,9 +2405,7 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
 pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
 		unsigned long attrs)
 {
-	if (!dev_is_dma_coherent(dev))
-		return __get_dma_pgprot(attrs, prot);
-	return prot;
+	return __get_dma_pgprot(attrs, prot);
 }
 
 void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 1d3f0b5a9940..bd2b039f43a6 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -14,9 +14,7 @@
 pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
 		unsigned long attrs)
 {
-	if (!dev_is_dma_coherent(dev) || (attrs & DMA_ATTR_WRITE_COMBINE))
-		return pgprot_writecombine(prot);
-	return prot;
+	return pgprot_writecombine(prot);
 }
 
 void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 77f6ebf97113..d8dcd8820369 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -121,7 +121,6 @@ config PPC
 	select ARCH_32BIT_OFF_T if PPC32
 	select ARCH_HAS_DEBUG_VIRTUAL
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
-	select ARCH_HAS_DMA_MMAP_PGPROT
 	select ARCH_HAS_ELF_RANDOMIZE
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
diff --git a/arch/powerpc/kernel/dma-common.c b/arch/powerpc/kernel/dma-common.c
deleted file mode 100644
index dc7ef6b17b69..000000000000
--- a/arch/powerpc/kernel/dma-common.c
+++ /dev/null
@@ -1,17 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * Contains common dma routines for all powerpc platforms.
- *
- * Copyright (C) 2019 Shawn Anastasio.
- */
-
-#include <linux/mm.h>
-#include <linux/dma-noncoherent.h>
-
-pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
-		unsigned long attrs)
-{
-	if (!dev_is_dma_coherent(dev))
-		return pgprot_noncached(prot);
-	return prot;
-}
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index a7f9c3edbcb2..0015fe610b23 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -574,7 +574,7 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
 	struct iova_domain *iovad = &cookie->iovad;
 	bool coherent = dev_is_dma_coherent(dev);
 	int ioprot = dma_info_to_prot(DMA_BIDIRECTIONAL, coherent, attrs);
-	pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);
+	pgprot_t prot = dma_pgprot(dev, PAGE_KERNEL, attrs);
 	unsigned int count, min_size, alloc_sizes = domain->pgsize_bitmap;
 	struct page **pages;
 	struct sg_table sgt;
@@ -975,7 +975,7 @@ static void *iommu_dma_alloc_pages(struct device *dev, size_t size,
 		return NULL;
 
 	if (IS_ENABLED(CONFIG_DMA_REMAP) && (!coherent || PageHighMem(page))) {
-		pgprot_t prot = arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs);
+		pgprot_t prot = dma_pgprot(dev, PAGE_KERNEL, attrs);
 
 		cpu_addr = dma_common_contiguous_remap(page, alloc_size,
 				VM_USERMAP, prot, __builtin_return_address(0));
@@ -1035,7 +1035,7 @@ static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 	unsigned long pfn, off = vma->vm_pgoff;
 	int ret;
 
-	vma->vm_page_prot = arch_dma_mmap_pgprot(dev, vma->vm_page_prot, attrs);
+	vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
 
 	if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
 		return ret;
diff --git a/include/linux/dma-noncoherent.h b/include/linux/dma-noncoherent.h
index 3813211a9aad..0bff3d7fac92 100644
--- a/include/linux/dma-noncoherent.h
+++ b/include/linux/dma-noncoherent.h
@@ -42,13 +42,18 @@ void arch_dma_free(struct device *dev, size_t size, void *cpu_addr,
 		dma_addr_t dma_addr, unsigned long attrs);
 long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
 		dma_addr_t dma_addr);
-
-#ifdef CONFIG_ARCH_HAS_DMA_MMAP_PGPROT
 pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
 		unsigned long attrs);
+
+#ifdef CONFIG_MMU
+pgprot_t dma_pgprot(struct device *dev, pgprot_t prot, unsigned long attrs);
 #else
-# define arch_dma_mmap_pgprot(dev, prot, attrs)	pgprot_noncached(prot)
-#endif
+static inline pgprot_t dma_pgprot(struct device *dev, pgprot_t prot,
+		unsigned long attrs)
+{
+	return prot;	/* no protection bits supported without page tables */
+}
+#endif /* CONFIG_MMU */
 
 #ifdef CONFIG_DMA_NONCOHERENT_CACHE_SYNC
 void arch_dma_cache_sync(struct device *dev, void *vaddr, size_t size,
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index b945239621d8..51d9657e0a8f 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -150,6 +150,21 @@ int dma_get_sgtable_attrs(struct device *dev, struct sg_table *sgt,
 }
 EXPORT_SYMBOL(dma_get_sgtable_attrs);
 
+/*
+ * Return the page attributes used for mapping dma_alloc_* memory, either in
+ * kernel space if remapping is needed, or to userspace through dma_mmap_*.
+ */
+pgprot_t dma_pgprot(struct device *dev, pgprot_t prot, unsigned long attrs)
+{
+	if (dev_is_dma_coherent(dev) ||
+	    (IS_ENABLED(CONFIG_DMA_NONCOHERENT_CACHE_SYNC) &&
+             (attrs & DMA_ATTR_NON_CONSISTENT)))
+		return prot;
+	if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_MMAP_PGPROT))
+		return arch_dma_mmap_pgprot(dev, prot, attrs);
+	return pgprot_noncached(prot);
+}
+
 /*
  * Create userspace mapping for the DMA-coherent memory.
  */
@@ -164,7 +179,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 	unsigned long pfn;
 	int ret = -ENXIO;
 
-	vma->vm_page_prot = arch_dma_mmap_pgprot(dev, vma->vm_page_prot, attrs);
+	vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
 
 	if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
 		return ret;
diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index a594aec07882..ffe78f0b2fe4 100644
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -218,7 +218,7 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 
 	/* create a coherent mapping */
 	ret = dma_common_contiguous_remap(page, size, VM_USERMAP,
-			arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs),
+			dma_pgprot(dev, PAGE_KERNEL, attrs),
 			__builtin_return_address(0));
 	if (!ret) {
 		__dma_direct_free_pages(dev, size, page);
-- 
2.20.1


^ permalink raw reply	[flat|nested] 5+ messages in thread

* [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE
  2019-08-07  6:16 fix default dma_mmap_* pgprot v3 Christoph Hellwig
  2019-08-07  6:16 ` [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_* Christoph Hellwig
@ 2019-08-07  6:16 ` Christoph Hellwig
  1 sibling, 0 replies; 5+ messages in thread
From: Christoph Hellwig @ 2019-08-07  6:16 UTC (permalink / raw)
  To: iommu
  Cc: Shawn Anastasio, Michael Ellerman, Russell King, Catalin Marinas,
	Will Deacon, Robin Murphy, Paul Burton, James Hogan,
	linuxppc-dev, linux-mips, linux-arm-kernel, linux-kernel

Mips uses the KSEG1 kernel memory segment to map dma coherent
allocations for non-coherent devices as uncacheable, and does not have
any kind of special support for DMA_ATTR_WRITE_COMBINE in the allocation
path.  Thus supporting DMA_ATTR_WRITE_COMBINE in dma_mmap_attrs will
lead to multiple mappings with different caching attributes.

Fixes: 8c172467be36 ("MIPS: Add implementation of dma_map_ops.mmap()")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/mips/Kconfig              | 1 -
 arch/mips/mm/dma-noncoherent.c | 8 --------
 2 files changed, 9 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d50fafd7bf3a..86e6760ef0d0 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1119,7 +1119,6 @@ config DMA_PERDEV_COHERENT
 
 config DMA_NONCOHERENT
 	bool
-	select ARCH_HAS_DMA_MMAP_PGPROT
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
 	select ARCH_HAS_UNCACHED_SEGMENT
 	select NEED_DMA_MAP_STATE
diff --git a/arch/mips/mm/dma-noncoherent.c b/arch/mips/mm/dma-noncoherent.c
index ed56c6fa7be2..1d4d57dd9acf 100644
--- a/arch/mips/mm/dma-noncoherent.c
+++ b/arch/mips/mm/dma-noncoherent.c
@@ -65,14 +65,6 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
 	return page_to_pfn(virt_to_page(cached_kernel_address(cpu_addr)));
 }
 
-pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
-		unsigned long attrs)
-{
-	if (attrs & DMA_ATTR_WRITE_COMBINE)
-		return pgprot_writecombine(prot);
-	return pgprot_noncached(prot);
-}
-
 static inline void dma_sync_virt(void *addr, size_t size,
 		enum dma_data_direction dir)
 {
-- 
2.20.1


^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE
  2019-08-05  8:01 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
@ 2019-08-05  8:06   ` Sergei Shtylyov
  0 siblings, 0 replies; 5+ messages in thread
From: Sergei Shtylyov @ 2019-08-05  8:06 UTC (permalink / raw)
  To: Christoph Hellwig, iommu
  Cc: Shawn Anastasio, Michael Ellerman, Russell King, Catalin Marinas,
	Will Deacon, Robin Murphy, Paul Burton, James Hogan,
	linuxppc-dev, linux-mips, linux-arm-kernel, linux-kernel

Hello!

On 05.08.2019 11:01, Christoph Hellwig wrote:

> Mips uses the KSEG1 kernel memory segment do map dma coherent

     MIPS. s/do/to/?

> allocations for n

on-coherent devices as uncachable, and does not have

    Uncacheable?

> any kind of special support for DMA_ATTR_WRITE_COMBINE in the allocation
> path.  Thus supporting DMA_ATTR_WRITE_COMBINE in dma_mmap_attrs will
> lead to multiple mappings with different caching attributes.
> 
> Fixes: 8c172467be36 ("MIPS: Add implementation of dma_map_ops.mmap()")
> Signed-off-by: Christoph Hellwig <hch@lst.de>
[...]

MBR, Sergei

^ permalink raw reply	[flat|nested] 5+ messages in thread

* [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE
  2019-08-05  8:01 fix default dma_mmap_* pgprot v2 Christoph Hellwig
@ 2019-08-05  8:01 ` Christoph Hellwig
  2019-08-05  8:06   ` Sergei Shtylyov
  0 siblings, 1 reply; 5+ messages in thread
From: Christoph Hellwig @ 2019-08-05  8:01 UTC (permalink / raw)
  To: iommu
  Cc: Shawn Anastasio, Michael Ellerman, Russell King, Catalin Marinas,
	Will Deacon, Robin Murphy, Paul Burton, James Hogan,
	linuxppc-dev, linux-mips, linux-arm-kernel, linux-kernel

Mips uses the KSEG1 kernel memory segment do map dma coherent
allocations for non-coherent devices as uncachable, and does not have
any kind of special support for DMA_ATTR_WRITE_COMBINE in the allocation
path.  Thus supporting DMA_ATTR_WRITE_COMBINE in dma_mmap_attrs will
lead to multiple mappings with different caching attributes.

Fixes: 8c172467be36 ("MIPS: Add implementation of dma_map_ops.mmap()")
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/mips/Kconfig              | 1 -
 arch/mips/mm/dma-noncoherent.c | 8 --------
 2 files changed, 9 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index d50fafd7bf3a..86e6760ef0d0 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1119,7 +1119,6 @@ config DMA_PERDEV_COHERENT
 
 config DMA_NONCOHERENT
 	bool
-	select ARCH_HAS_DMA_MMAP_PGPROT
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
 	select ARCH_HAS_UNCACHED_SEGMENT
 	select NEED_DMA_MAP_STATE
diff --git a/arch/mips/mm/dma-noncoherent.c b/arch/mips/mm/dma-noncoherent.c
index ed56c6fa7be2..1d4d57dd9acf 100644
--- a/arch/mips/mm/dma-noncoherent.c
+++ b/arch/mips/mm/dma-noncoherent.c
@@ -65,14 +65,6 @@ long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,
 	return page_to_pfn(virt_to_page(cached_kernel_address(cpu_addr)));
 }
 
-pgprot_t arch_dma_mmap_pgprot(struct device *dev, pgprot_t prot,
-		unsigned long attrs)
-{
-	if (attrs & DMA_ATTR_WRITE_COMBINE)
-		return pgprot_writecombine(prot);
-	return pgprot_noncached(prot);
-}
-
 static inline void dma_sync_virt(void *addr, size_t size,
 		enum dma_data_direction dir)
 {
-- 
2.20.1


^ permalink raw reply	[flat|nested] 5+ messages in thread

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Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2019-08-07  6:16 fix default dma_mmap_* pgprot v3 Christoph Hellwig
2019-08-07  6:16 ` [PATCH 1/2] dma-mapping: fix page attributes for dma_mmap_* Christoph Hellwig
2019-08-07  6:16 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
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2019-08-05  8:01 fix default dma_mmap_* pgprot v2 Christoph Hellwig
2019-08-05  8:01 ` [PATCH 2/2] MIPS: remove support for DMA_ATTR_WRITE_COMBINE Christoph Hellwig
2019-08-05  8:06   ` Sergei Shtylyov

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