Hi Laura,

Thanks for looking

On 23/01/15 17:42, Laura Abbott wrote:

On 1/12/2015 12:48 PM, Robin Murphy wrote:

quoted

Taking inspiration from the existing arch/arm code, break out some
generic functions to interface the DMA-API to the IOMMU-API. This will
do the bulk of the heavy lifting for IOMMU-backed dma-mapping.

Whilst the target is arm64, rather than introduce yet another private
implementation, place this in common code as the first step towards
consolidating the numerous versions spread around between architecture
code and IOMMU drivers.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
---
   include/linux/dma-iommu.h |  78 ++++++++
   lib/Kconfig               |   8 +
   lib/Makefile              |   1 +
   lib/dma-iommu.c           | 455 ++++++++++++++++++++++++++++++++++++++++++++++
   4 files changed, 542 insertions(+)
   create mode 100644 include/linux/dma-iommu.h
   create mode 100644 lib/dma-iommu.c

diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
new file mode 100644
index 0000000..4515407
--- /dev/null
+++ b/include/linux/dma-iommu.h

<snip>

quoted

+
+struct iommu_dma_mapping *iommu_dma_create_mapping(struct iommu_ops *ops,
+		dma_addr_t base, size_t size)
+{
+	struct iommu_dma_mapping *mapping;
+	struct iommu_domain *domain;
+	struct iova_domain *iovad;
+	struct iommu_domain_geometry *dg;
+	unsigned long order, base_pfn, end_pfn;
+
+	pr_debug("base=%pad\tsize=0x%zx\n", &base, size);
+	mapping = kzalloc(sizeof(*mapping), GFP_KERNEL);
+	if (!mapping)
+		return NULL;
+
+	/*
+	 * HACK: We'd like to ask the relevant IOMMU in ops for a suitable
+	 * domain, but until that happens, bypass the bus nonsense and create
+	 * one directly for this specific device/IOMMU combination...
+	 */
+	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
+
+	if (!domain)
+		goto out_free_mapping;
+	domain->ops = ops;
+
+	if (ops->domain_init(domain))
+		goto out_free_mapping;
+	/*
+	 * ...and do the bare minimum to sanity-check that the domain allows
+	 * at least some access to the device...
+	 */
+	dg = &domain->geometry;
+	if (!(base < dg->aperture_end && base + size > dg->aperture_start)) {
+		pr_warn("DMA range outside IOMMU capability; is DT correct?\n");
+		goto out_free_mapping;
+	}

This check seems to always fail with base = 0 because dg->aperture_end is
always going to be 0 as well. base <= dg->aperature_end ?

Strictly you're right, since aperture_end should be the highest mappable 
address thus you could create a valid, if a little silly, 1-byte domain 
if both were zero. However, it shouldn't really be zero.

I put this bit in since the majority of IOMMU drivers set up the 
geometry in domain_init and it seemed worth making use of. The ARM SMMU 
driver is currently one of the odd ones out that don't, however one of 
my as-yet-unpublished patches porting it to the new of_iommu_configure 
framework involves fixing domain initialisation and adds geometry setup 
as well - that's what I've been testing with. I'm hoping to get that 
series out soon, but among other things it needs a messy merge with 
Will's pagetable changes.

Robin.