[Xen-devel] [PATCH 07 of 14] swiotlb: add arch hook to force mapping

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

From: Ian Campbell <ian.campbell@xxxxxxxxxx>

Some architectures require special rules to determine whether a range
needs mapping or not.  This adds a weak function for architectures to
override.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
 include/linux/swiotlb.h |    2 ++
 lib/swiotlb.c           |   15 +++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -30,6 +30,8 @@
 extern dma_addr_t swiotlb_phys_to_bus(phys_addr_t address);
 extern phys_addr_t swiotlb_bus_to_phys(dma_addr_t address);
 
+extern int swiotlb_arch_range_needs_mapping(void *ptr, size_t size);
+
 extern void
 *swiotlb_alloc_coherent(struct device *hwdev, size_t size,
                        dma_addr_t *dma_handle, gfp_t flags);
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -145,6 +145,11 @@
        return phys_to_virt(swiotlb_bus_to_phys(address));
 }
 
+int __weak swiotlb_arch_range_needs_mapping(void *ptr, size_t size)
+{
+       return 0;
+}
+
 /*
  * Statically reserve bounce buffer space and initialize bounce buffer data
  * structures for the software IO TLB used to implement the DMA API.
@@ -297,6 +302,11 @@
        return !is_buffer_dma_capable(dma_get_mask(hwdev), addr, size);
 }
 
+static inline int range_needs_mapping(void *ptr, size_t size)
+{
+       return swiotlb_force || swiotlb_arch_range_needs_mapping(ptr, size);
+}
+
 static int is_swiotlb_buffer(char *addr)
 {
        return addr >= io_tlb_start && addr < io_tlb_end;
@@ -581,7 +591,8 @@
         * we can safely return the device addr and not worry about bounce
         * buffering it.
         */
-       if (!address_needs_mapping(hwdev, dev_addr, size) && !swiotlb_force)
+       if (!address_needs_mapping(hwdev, dev_addr, size) &&
+           !range_needs_mapping(ptr, size))
                return dev_addr;
 
        /*
@@ -741,7 +752,7 @@
        for_each_sg(sgl, sg, nelems, i) {
                addr = SG_ENT_VIRT_ADDRESS(sg);
                dev_addr = swiotlb_virt_to_bus(addr);
-               if (swiotlb_force ||
+               if (range_needs_mapping(sg_virt(sg), sg->length) ||
                    address_needs_mapping(hwdev, dev_addr, sg->length)) {
                        void *map = map_single(hwdev, addr, sg->length, dir);
                        if (!map) {



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