xen-swiotlb: Fix wrong panic.

Propagate the baremetal git commit "swiotlb: fix wrong panic"
(fba99fa38b023224680308a482e12a0eca87e4e1) in the Xen-SWIOTLB version.
wherein swiotlb's map_page wrongly calls panic() when it can't find
a buffer fit for device's dma mask.  It should return an error instead.

Devices with an odd dma mask (i.e.  under 4G) like b44 network card hit
this bug (the system crashes):

http://marc.info/?l=linux-kernel&m=129648943830106&w=2

If xen-swiotlb returns an error, b44 driver can use the own bouncing
mechanism.

CC: stable@kernel.org
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
(cherry picked from commit ab2a47bd242d6cdcf6b2b64797f271c6f0a6d338)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 89f7c972286562fb2078718a0853a685f3dd8e31..389298ab831ada4be336ded0f7134696c26fc2d7 100644 (file)
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -293,9 +293,10 @@ dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
        /*
         * Ensure that the address returned is DMA'ble
         */
-       if (!dma_capable(dev, dev_addr, size))
-               panic("map_single: bounce buffer is not DMA'ble");
-
+       if (!dma_capable(dev, dev_addr, size)) {
+               swiotlb_tbl_unmap_single(dev, map, size, dir);
+               dev_addr = 0;
+       }
        return dev_addr;
 }
 EXPORT_SYMBOL_GPL(xen_swiotlb_map_page);