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ARM64: dma-mapping: fix handling of devices registered before arch_initcall

PATCH New Marek Szyprowski 2 participants 4 messages Feb 16, 2016 – Feb 17, 2016 arm64

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Marek Szyprowski

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#0 lore raw

PATCH 1/1 ARM64: dma-mapping: fix handling of devices registered before arch_initcall

This patch ensures that devices, which got registered before arch_initcall will be handled correctly by IOMMU-based DMA-mapping code.

Signed-off-by Marek Szyprowski <[email protected]>
---
 arch/arm64/mm/dma-mapping.c | 4 ++++
 1 file changed, 4 insertions(+)
arch/arm64/mm/dma-mapping.c +4 -0
index 573b1e6..ce6019f 100644
@@ -928,6 +928,10 @@ static int __init __iommu_dma_init(void)
 		ret = register_iommu_dma_ops_notifier(&platform_bus_type);
 	if (!ret)
 		ret = register_iommu_dma_ops_notifier(&amba_bustype);
+
+	/* handle devices queued before this arch_initcall */
+	if (!ret)
+		__iommu_attach_notifier(NULL, BUS_NOTIFY_ADD_DEVICE, NULL);
 	return ret;
 }
 arch_initcall(__iommu_dma_init);
Signature · 1 line
1.9.2
#1 lore raw

PATCH 1/1 ARM64: dma-mapping: fix handling of devices registered before arch_initcall

Quoted 13 lines · Marek Szyprowski

This patch ensures that devices, which got registered before arch_initcall will be handled correctly by IOMMU-based DMA-mapping code.

Signed-off-by Marek Szyprowski <[email protected]>
---
  arch/arm64/mm/dma-mapping.c | 4 ++++
  1 file changed, 4 insertions(+)
arch/arm64/mm/dma-mapping.c +0 -0
index 573b1e6..ce6019f 100644

arch/arm64/mm/dma-mapping.c static int __init __iommu_dma_init(void) · line 934

Quoted 7 lines
arch/arm64/mm/dma-mapping.c +4 -0
@@ -928,6 +928,10 @@ static int __init __iommu_dma_init(void)
  		ret = register_iommu_dma_ops_notifier(&platform_bus_type);
  	if (!ret)
  		ret = register_iommu_dma_ops_notifier(&amba_bustype);
+
+	/* handle devices queued before this arch_initcall */
+	if (!ret)
+		__iommu_attach_notifier(NULL, BUS_NOTIFY_ADD_DEVICE, NULL);

Hmm, surely unless *all* the devices on the relevant buses are created before arch_initcall level, then the next one is going to kick off the notifier to walk the whole list anyway. Have you seen this being a problem in practice?

Robin.

Quoted 4 lines
arch/arm64/mm/dma-mapping.c +0 -0
  	return ret;
  }
  arch_initcall(__iommu_dma_init);
author
#2 lore raw

PATCH 1/1 ARM64: dma-mapping: fix handling of devices registered before arch_initcall

Hello,

Quoted 19 lines · Robin Murphy
Quoted 18 lines · Marek Szyprowski

This patch ensures that devices, which got registered before arch_initcall
will be handled correctly by IOMMU-based DMA-mapping code.

Signed-off-by Marek Szyprowski <[email protected]>
---
  arch/arm64/mm/dma-mapping.c | 4 ++++
  1 file changed, 4 insertions(+)
arch/arm64/mm/dma-mapping.c +1 -0
index 573b1e6..ce6019f 100644
@@ -928,6 +928,10 @@ static int __init __iommu_dma_init(void)
          ret = register_iommu_dma_ops_notifier(&platform_bus_type);
      if (!ret)
          ret = register_iommu_dma_ops_notifier(&amba_bustype);
+
Quoted 8 lines

arch/arm64/mm/dma-mapping.c static int __init __iommu_dma_init(void) · line 934

Quoted 3 lines
arch/arm64/mm/dma-mapping.c +3 -0
+    /* handle devices queued before this arch_initcall */
+    if (!ret)
+        __iommu_attach_notifier(NULL, BUS_NOTIFY_ADD_DEVICE, NULL);

Hmm, surely unless *all* the devices on the relevant buses are created before arch_initcall level, then the next one is going to kick off the notifier to walk the whole list anyway. Have you seen this being a problem in practice?

Yes, I've observed such situation, that's why I've posted this patch. I was really surprised that this code doesn't handle all cases.

Best regards

Signature · 2 lines
Marek Szyprowski, PhD
Samsung R&D Institute Poland
#3 lore raw

PATCH 1/1 ARM64: dma-mapping: fix handling of devices registered before arch_initcall

Quoted 31 lines · Marek Szyprowski

Hello,

Quoted 19 lines · Robin Murphy
Quoted 18 lines · Marek Szyprowski

This patch ensures that devices, which got registered before arch_initcall
will be handled correctly by IOMMU-based DMA-mapping code.

Signed-off-by Marek Szyprowski <[email protected]>
---
  arch/arm64/mm/dma-mapping.c | 4 ++++
  1 file changed, 4 insertions(+)
arch/arm64/mm/dma-mapping.c +1 -0
index 573b1e6..ce6019f 100644
@@ -928,6 +928,10 @@ static int __init __iommu_dma_init(void)
          ret = register_iommu_dma_ops_notifier(&platform_bus_type);
      if (!ret)
          ret = register_iommu_dma_ops_notifier(&amba_bustype);
+
Quoted 8 lines

arch/arm64/mm/dma-mapping.c static int __init __iommu_dma_init(void) · line 934

Quoted 3 lines
arch/arm64/mm/dma-mapping.c +3 -0
+    /* handle devices queued before this arch_initcall */
+    if (!ret)
+        __iommu_attach_notifier(NULL, BUS_NOTIFY_ADD_DEVICE, NULL);

Hmm, surely unless *all* the devices on the relevant buses are created before arch_initcall level, then the next one is going to kick off the notifier to walk the whole list anyway. Have you seen this being a problem in practice?

Quoted 2 lines

Yes, I've observed such situation, that's why I've posted this patch. I was really surprised that this code doesn't handle all cases.

Ok, fair enough - I guess I just didn't consider that being a likely possibility. Since I am a fan of correctness:

Acked-by Robin Murphy <[email protected]>

Thanks,
Robin.

Quoted 2 lines

Best regards