Re: [PATCH 1/3] dma-direct: unify the dma_capable definitions

[Christoph Hellwig <hch@lst.de>]

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On Tue, Nov 19, 2019 at 11:26:39AM +0100, Marek Szyprowski wrote:
> Christoph: Let me know if this is a proper fix for you, then I will send 
> it as a full patch.

Besides the point from Robin, which is really older than you patch
I'm not a fan of duplicating dma_capable here.  Let me know what you
think of the two attached patches.

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From db897c2ec63e7af78137c533c9f821c594896167 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 19 Nov 2019 17:35:36 +0100
Subject: dma-direct: don't check swiotlb=force in dma_direct_map_resource

When mapping resources we can't just use swiotlb ram for bounce
buffering.  Switch to a direct dma_capable check instead.

Fixes: cfced786969c ("dma-mapping: remove the default map_resource implementation")
Reported-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 kernel/dma/direct.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 077876ae5c74..a479bd2d1e8b 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -412,7 +412,7 @@ dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
 {
 	dma_addr_t dma_addr = paddr;
 
-	if (unlikely(!dma_direct_possible(dev, dma_addr, size))) {
+	if (unlikely(!dma_capable(dev, dma_addr, size))) {
 		report_addr(dev, dma_addr, size);
 		return DMA_MAPPING_ERROR;
 	}
-- 
2.20.1


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From fd82d238a42e3a5f12dd0621db2c724b89509b02 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@lst.de>
Date: Tue, 19 Nov 2019 17:38:58 +0100
Subject: dma-direct: exclude dma_direct_map_resource from the min_low_pfn
 check

The valid memory address check in dma_capable only makes sense when mapping
normal memory, not when using dma_map_resource to map a device resource.
Add a new boolean argument to dma_capable to exclude that check for the
dma_map_resource case.

Fixes: b12d66278dd6 ("dma-direct: check for overflows on 32 bit DMA addresses")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 arch/x86/kernel/amd_gart_64.c | 4 ++--
 drivers/xen/swiotlb-xen.c     | 4 ++--
 include/linux/dma-direct.h    | 5 +++--
 kernel/dma/direct.c           | 4 ++--
 kernel/dma/swiotlb.c          | 2 +-
 5 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index a6ac3712db8b..5cfab41e8509 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -185,13 +185,13 @@ static void iommu_full(struct device *dev, size_t size, int dir)
 static inline int
 need_iommu(struct device *dev, unsigned long addr, size_t size)
 {
-	return force_iommu || !dma_capable(dev, addr, size);
+	return force_iommu || !dma_capable(dev, addr, size, true);
 }
 
 static inline int
 nonforced_iommu(struct device *dev, unsigned long addr, size_t size)
 {
-	return !dma_capable(dev, addr, size);
+	return !dma_capable(dev, addr, size, true);
 }
 
 /* Map a single continuous physical area into the IOMMU.
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 3f8b2cdb4acb..b6d27762c6f8 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -375,7 +375,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	 * we can safely return the device addr and not worry about bounce
 	 * buffering it.
 	 */
-	if (dma_capable(dev, dev_addr, size) &&
+	if (dma_capable(dev, dev_addr, size, true) &&
 	    !range_straddles_page_boundary(phys, size) &&
 		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
 		swiotlb_force != SWIOTLB_FORCE)
@@ -397,7 +397,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
 	/*
 	 * Ensure that the address returned is DMA'ble
 	 */
-	if (unlikely(!dma_capable(dev, dev_addr, size))) {
+	if (unlikely(!dma_capable(dev, dev_addr, size, true))) {
 		swiotlb_tbl_unmap_single(dev, map, size, size, dir,
 				attrs | DMA_ATTR_SKIP_CPU_SYNC);
 		return DMA_MAPPING_ERROR;
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index f8959f75e496..99b77dd5f79b 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -49,14 +49,15 @@ static inline phys_addr_t dma_to_phys(struct device *dev, dma_addr_t daddr)
 	return __sme_clr(__dma_to_phys(dev, daddr));
 }
 
-static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
+static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size,
+		bool is_ram)
 {
 	dma_addr_t end = addr + size - 1;
 
 	if (!dev->dma_mask)
 		return false;
 
-	if (!IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) &&
+	if (is_ram && !IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) &&
 	    min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
 		return false;
 
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index a479bd2d1e8b..40f1f0aac4b1 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -363,7 +363,7 @@ static inline bool dma_direct_possible(struct device *dev, dma_addr_t dma_addr,
 		size_t size)
 {
 	return swiotlb_force != SWIOTLB_FORCE &&
-		dma_capable(dev, dma_addr, size);
+		dma_capable(dev, dma_addr, size, true);
 }
 
 dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
@@ -412,7 +412,7 @@ dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
 {
 	dma_addr_t dma_addr = paddr;
 
-	if (unlikely(!dma_capable(dev, dma_addr, size))) {
+	if (unlikely(!dma_capable(dev, dma_addr, size, false))) {
 		report_addr(dev, dma_addr, size);
 		return DMA_MAPPING_ERROR;
 	}
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 673a2cdb2656..9280d6f8271e 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -678,7 +678,7 @@ bool swiotlb_map(struct device *dev, phys_addr_t *phys, dma_addr_t *dma_addr,
 
 	/* Ensure that the address returned is DMA'ble */
 	*dma_addr = __phys_to_dma(dev, *phys);
-	if (unlikely(!dma_capable(dev, *dma_addr, size))) {
+	if (unlikely(!dma_capable(dev, *dma_addr, size, true))) {
 		swiotlb_tbl_unmap_single(dev, *phys, size, size, dir,
 			attrs | DMA_ATTR_SKIP_CPU_SYNC);
 		return false;
-- 
2.20.1