Allow loading the same DMA address multiple times without any prior

unload for the LinuxKPI.

Reviewed by:	kib, zeising
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D20181

1 files changed, 27 insertions, 0 deletions

diff --git a/sys/compat/linuxkpi/common/src/linux_pci.c b/sys/compat/linuxkpi/common/src/linux_pci.c
index ff559b0eb0fc..8de6968a7de0 100644
--- a/sys/compat/linuxkpi/common/src/linux_pci.c
+++ b/sys/compat/linuxkpi/common/src/linux_pci.c
@@ -520,6 +520,7 @@ linux_dma_alloc_coherent(struct device *dev, size_t size,
 	return (mem);
 }
 
+#if defined(__i386__) || defined(__amd64__) || defined(__aarch64__)
 dma_addr_t
 linux_dma_map_phys(struct device *dev, vm_paddr_t phys, size_t len)
 {
@@ -530,6 +531,15 @@ linux_dma_map_phys(struct device *dev, vm_paddr_t phys, size_t len)
 
 	priv = dev->dma_priv;
 
+	/*
+	 * If the resultant mapping will be entirely 1:1 with the
+	 * physical address, short-circuit the remainder of the
+	 * bus_dma API.  This avoids tracking collisions in the pctrie
+	 * with the additional benefit of reducing overhead.
+	 */
+	if (bus_dma_id_mapped(priv->dmat, phys, len))
+		return (phys);
+
 	obj = uma_zalloc(linux_dma_obj_zone, 0);
 
 	DMA_PRIV_LOCK(priv);
@@ -562,7 +572,15 @@ linux_dma_map_phys(struct device *dev, vm_paddr_t phys, size_t len)
 	DMA_PRIV_UNLOCK(priv);
 	return (obj->dma_addr);
 }
+#else
+dma_addr_t
+linux_dma_map_phys(struct device *dev, vm_paddr_t phys, size_t len)
+{
+	return (phys);
+}
+#endif
 
+#if defined(__i386__) || defined(__amd64__) || defined(__aarch64__)
 void
 linux_dma_unmap(struct device *dev, dma_addr_t dma_addr, size_t len)
 {
@@ -571,6 +589,9 @@ linux_dma_unmap(struct device *dev, dma_addr_t dma_addr, size_t len)
 
 	priv = dev->dma_priv;
 
+	if (pctrie_is_empty(&priv->ptree))
+		return;
+
 	DMA_PRIV_LOCK(priv);
 	obj = LINUX_DMA_PCTRIE_LOOKUP(&priv->ptree, dma_addr);
 	if (obj == NULL) {
@@ -584,6 +605,12 @@ linux_dma_unmap(struct device *dev, dma_addr_t dma_addr, size_t len)
 
 	uma_zfree(linux_dma_obj_zone, obj);
 }
+#else
+void
+linux_dma_unmap(struct device *dev, dma_addr_t dma_addr, size_t len)
+{
+}
+#endif
 
 int
 linux_dma_map_sg_attrs(struct device *dev, struct scatterlist *sgl, int nents,