[dma] Provide dma_umalloc() for allocating large DMA-coherent buffers

Some devices (e.g. xHCI USB host controllers) may require the use of
large areas of host memory for private use by the device.  These
allocations cannot be satisfied from iPXE's limited heap space, and so
are currently allocated using umalloc() which will allocate external
system memory (and alter the system memory map as needed).

Provide dma_umalloc() to provide such allocations as part of the DMA
API, since there is otherwise no way to guarantee that the allocated
regions are usable for coherent DMA.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/interface/efi/efi_pci.c

@@ -504,6 +504,38 @@ static void efipci_dma_free ( struct dma_device *dma, struct dma_mapping *map,
 		dma->allocated--;
 }
 
+/**
+ * Allocate and map DMA-coherent buffer from external (user) memory
+ *
+ * @v dma		DMA device
+ * @v map		DMA mapping to fill in
+ * @v len		Length of buffer
+ * @v align		Physical alignment
+ * @ret addr		Buffer address, or NULL on error
+ */
+static userptr_t efipci_dma_umalloc ( struct dma_device *dma,
+				      struct dma_mapping *map,
+				      size_t len, size_t align ) {
+	void *addr;
+
+	addr = efipci_dma_alloc ( dma, map, len, align );
+	return virt_to_user ( addr );
+}
+
+/**
+ * Unmap and free DMA-coherent buffer from external (user) memory
+ *
+ * @v dma		DMA device
+ * @v map		DMA mapping
+ * @v addr		Buffer address
+ * @v len		Length of buffer
+ */
+static void efipci_dma_ufree ( struct dma_device *dma, struct dma_mapping *map,
+			       userptr_t addr, size_t len ) {
+
+	efipci_dma_free ( dma, map, user_to_virt ( addr, 0 ), len );
+}
+
 /**
  * Set addressable space mask
  *
@@ -542,6 +574,8 @@ static struct dma_operations efipci_dma_operations = {
 	.unmap = efipci_dma_unmap,
 	.alloc = efipci_dma_alloc,
 	.free = efipci_dma_free,
+	.umalloc = efipci_dma_umalloc,
+	.ufree = efipci_dma_ufree,
 	.set_mask = efipci_dma_set_mask,
 };