diff mbox series

[1/4] vmalloc: lift the arm flag for coherent mappings to common code

Message ID 20190830062924.21714-2-hch@lst.de (mailing list archive)
State New, archived
Headers show
Series [1/4] vmalloc: lift the arm flag for coherent mappings to common code | expand

Commit Message

Christoph Hellwig Aug. 30, 2019, 6:29 a.m. UTC 
The arm architecture had a VM_ARM_DMA_CONSISTENT flag to mark DMA
coherent remapping for a while.  Lift this flag to common code so
that we can use it generically.  We also check it in the only place
VM_USERMAP is directly check so that we can entirely replace that
flag as well (although I'm not even sure why we'd want to allow
remapping DMA appings, but I'd rather not change behavior).

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/arm/mm/dma-mapping.c | 22 +++++++---------------
 arch/arm/mm/mm.h          |  3 ---
 include/linux/vmalloc.h   |  2 ++
 mm/vmalloc.c              |  5 ++++-
 4 files changed, 13 insertions(+), 19 deletions(-)

Comments

Russell King (Oracle) Aug. 30, 2019, 9:29 a.m. UTC | #1 
On Fri, Aug 30, 2019 at 08:29:21AM +0200, Christoph Hellwig wrote:
> The arm architecture had a VM_ARM_DMA_CONSISTENT flag to mark DMA
> coherent remapping for a while.  Lift this flag to common code so
> that we can use it generically.  We also check it in the only place
> VM_USERMAP is directly check so that we can entirely replace that
> flag as well (although I'm not even sure why we'd want to allow
> remapping DMA appings, but I'd rather not change behavior).

Good, because if you did change that behaviour, you'd break almost
every ARM framebuffer and cripple ARM audio drivers.
Christoph Hellwig Aug. 30, 2019, 2:59 p.m. UTC | #2 
On Fri, Aug 30, 2019 at 10:29:18AM +0100, Russell King - ARM Linux admin wrote:
> On Fri, Aug 30, 2019 at 08:29:21AM +0200, Christoph Hellwig wrote:
> > The arm architecture had a VM_ARM_DMA_CONSISTENT flag to mark DMA
> > coherent remapping for a while.  Lift this flag to common code so
> > that we can use it generically.  We also check it in the only place
> > VM_USERMAP is directly check so that we can entirely replace that
> > flag as well (although I'm not even sure why we'd want to allow
> > remapping DMA appings, but I'd rather not change behavior).
> 
> Good, because if you did change that behaviour, you'd break almost
> every ARM framebuffer and cripple ARM audio drivers.

How would that break them?  All the usual video and audio drivers that
use dma_alloc_* then use dma_mmap_* which never end up in the only place
that actually checks VM_USERMAP (remap_vmalloc_range_partial) as they
end up in the dma_map_ops mmap methods which contain what is effecitvely
open coded versions of that routine.  There are very few callers of
remap_vmalloc_range_partial / remap_vmalloc_range, and while a few of
those actually are in media drivers and the virtual frame buffer video
driver, none of these seems to be called on dma memory (which would
be a layering violation anyway).
diff mbox series

Patch

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index d42557ee69c2..5c0af4a2faa7 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -340,19 +340,13 @@  static void *
 __dma_alloc_remap(struct page *page, size_t size, gfp_t gfp, pgprot_t prot,
 	const void *caller)
 {
-	/*
-	 * DMA allocation can be mapped to user space, so lets
-	 * set VM_USERMAP flags too.
-	 */
-	return dma_common_contiguous_remap(page, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP,
+	return dma_common_contiguous_remap(page, size, VM_DMA_COHERENT,
 			prot, caller);
 }
 
 static void __dma_free_remap(void *cpu_addr, size_t size)
 {
-	dma_common_free_remap(cpu_addr, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP);
+	dma_common_free_remap(cpu_addr, size, VM_DMA_COHERENT);
 }
 
 #define DEFAULT_DMA_COHERENT_POOL_SIZE	SZ_256K
@@ -1379,8 +1373,8 @@  static void *
 __iommu_alloc_remap(struct page **pages, size_t size, gfp_t gfp, pgprot_t prot,
 		    const void *caller)
 {
-	return dma_common_pages_remap(pages, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP, prot, caller);
+	return dma_common_pages_remap(pages, size, VM_DMA_COHERENT, prot,
+			caller);
 }
 
 /*
@@ -1464,7 +1458,7 @@  static struct page **__iommu_get_pages(void *cpu_addr, unsigned long attrs)
 		return cpu_addr;
 
 	area = find_vm_area(cpu_addr);
-	if (area && (area->flags & VM_ARM_DMA_CONSISTENT))
+	if (area && (area->flags & VM_DMA_COHERENT))
 		return area->pages;
 	return NULL;
 }
@@ -1622,10 +1616,8 @@  void __arm_iommu_free_attrs(struct device *dev, size_t size, void *cpu_addr,
 		return;
 	}
 
-	if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0) {
-		dma_common_free_remap(cpu_addr, size,
-			VM_ARM_DMA_CONSISTENT | VM_USERMAP);
-	}
+	if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) == 0)
+		dma_common_free_remap(cpu_addr, size, VM_DMA_COHERENT);
 
 	__iommu_remove_mapping(dev, handle, size);
 	__iommu_free_buffer(dev, pages, size, attrs);
diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
index 941356d95a67..88c121ac14b3 100644
--- a/arch/arm/mm/mm.h
+++ b/arch/arm/mm/mm.h
@@ -70,9 +70,6 @@  extern void __flush_dcache_page(struct address_space *mapping, struct page *page
 #define VM_ARM_MTYPE(mt)		((mt) << 20)
 #define VM_ARM_MTYPE_MASK	(0x1f << 20)
 
-/* consistent regions used by dma_alloc_attrs() */
-#define VM_ARM_DMA_CONSISTENT	0x20000000
-
 
 struct static_vm {
 	struct vm_struct vm;
diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 9b21d0047710..dfa718ffdd4f 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -18,6 +18,7 @@  struct notifier_block;		/* in notifier.h */
 #define VM_ALLOC		0x00000002	/* vmalloc() */
 #define VM_MAP			0x00000004	/* vmap()ed pages */
 #define VM_USERMAP		0x00000008	/* suitable for remap_vmalloc_range */
+#define VM_DMA_COHERENT		0x00000010	/* dma_alloc_coherent */
 #define VM_UNINITIALIZED	0x00000020	/* vm_struct is not fully initialized */
 #define VM_NO_GUARD		0x00000040      /* don't add guard page */
 #define VM_KASAN		0x00000080      /* has allocated kasan shadow memory */
@@ -26,6 +27,7 @@  struct notifier_block;		/* in notifier.h */
  * vfree_atomic().
  */
 #define VM_FLUSH_RESET_PERMS	0x00000100      /* Reset direct map and flush TLB on unmap */
+
 /* bits [20..32] reserved for arch specific ioremap internals */
 
 /*
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 7ba11e12a11f..c1246d77cf75 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2993,7 +2993,7 @@  int remap_vmalloc_range_partial(struct vm_area_struct *vma, unsigned long uaddr,
 	if (!area)
 		return -EINVAL;
 
-	if (!(area->flags & VM_USERMAP))
+	if (!(area->flags & (VM_USERMAP | VM_DMA_COHERENT)))
 		return -EINVAL;
 
 	if (kaddr + size > area->addr + get_vm_area_size(area))
@@ -3496,6 +3496,9 @@  static int s_show(struct seq_file *m, void *p)
 	if (v->flags & VM_USERMAP)
 		seq_puts(m, " user");
 
+	if (v->flags & VM_DMA_COHERENT)
+		seq_puts(m, " dma-coherent");
+
 	if (is_vmalloc_addr(v->pages))
 		seq_puts(m, " vpages");