On 2024/10/27 22:21, Leon Romanovsky wrote:
From: Leon Romanovsky<leonro@xxxxxxxxxx>
The existing .map_page() callback provides both allocating of IOVA
and linking DMA pages. That combination works great for most of the
callers who use it in control paths, but is less effective in fast
paths where there may be multiple calls to map_page().
These advanced callers already manage their data in some sort of
database and can perform IOVA allocation in advance, leaving range
linkage operation to be in fast path.
Provide an interface to allocate/deallocate IOVA and next patch
link/unlink DMA ranges to that specific IOVA.
The API is exported from dma-iommu as it is the only implementation
supported, the namespace is clearly different from iommu_* functions
which are not allowed to be used. This code layout allows us to save
function call per API call used in datapath as well as a lot of boilerplate
code.
Signed-off-by: Leon Romanovsky<leonro@xxxxxxxxxx>
---
drivers/iommu/dma-iommu.c | 79 +++++++++++++++++++++++++++++++++++++
include/linux/dma-mapping.h | 15 +++++++
2 files changed, 94 insertions(+)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index c422e36c0d66..0644152c5aad 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1745,6 +1745,85 @@ size_t iommu_dma_max_mapping_size(struct device *dev)
return SIZE_MAX;
}
+static bool iommu_dma_iova_alloc(struct device *dev,
+ struct dma_iova_state *state, phys_addr_t phys, size_t size)
+{
+ struct iommu_domain *domain = iommu_get_dma_domain(dev);
+ struct iommu_dma_cookie *cookie = domain->iova_cookie;
+ struct iova_domain *iovad = &cookie->iovad;
+ size_t iova_off = iova_offset(iovad, phys);
+ dma_addr_t addr;
+
+ if (WARN_ON_ONCE(!size))
+ return false;
+ if (WARN_ON_ONCE(size & DMA_IOVA_USE_SWIOTLB))
+ return false;
+
+ addr = iommu_dma_alloc_iova(domain,
+ iova_align(iovad, size + iova_off),
+ dma_get_mask(dev), dev);
+ if (!addr)
+ return false;
+
+ state->addr = addr + iova_off;
+ state->__size = size;
+ return true;
+}
+
+/**
+ * dma_iova_try_alloc - Try to allocate an IOVA space
+ * @dev: Device to allocate the IOVA space for
+ * @state: IOVA state
+ * @phys: physical address
I'm curious to know why a physical address is necessary for IOVA space
allocation. Could you please elaborate?
+ * @size: IOVA size
+ *
+ * Check if @dev supports the IOVA-based DMA API, and if yes allocate IOVA space
+ * for the given base address and size.
+ *
+ * Note: @phys is only used to calculate the IOVA alignment. Callers that always
+ * do PAGE_SIZE aligned transfers can safely pass 0 here.
+ *
+ * Returns %true if the IOVA-based DMA API can be used and IOVA space has been
+ * allocated, or %false if the regular DMA API should be used.
+ */
+bool dma_iova_try_alloc(struct device *dev, struct dma_iova_state *state,
+ phys_addr_t phys, size_t size)
+{
+ memset(state, 0, sizeof(*state));
+ if (!use_dma_iommu(dev))
+ return false;
+ if (static_branch_unlikely(&iommu_deferred_attach_enabled) &&
+ iommu_deferred_attach(dev, iommu_get_domain_for_dev(dev)))
+ return false;
+ return iommu_dma_iova_alloc(dev, state, phys, size);
+}
+EXPORT_SYMBOL_GPL(dma_iova_try_alloc);
Thanks,
baolu
