Xen devel - Nov 2010 - [PATCH] agp: use DMA API when compiled for Xen as well

Xen guests need translation between pseudo-physical and real machine
physical addresses when accessing graphics devices, so use the DMA API
in that case too.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

diff --git a/drivers/char/agp/intel-gtt.c b/drivers/char/agp/intel-gtt.c
index 75e0a34..ce63e5c 100644
--- a/drivers/char/agp/intel-gtt.c
+++ b/drivers/char/agp/intel-gtt.c
@@ -20,8 +20,12 @@
  * an Intel IOMMU. So make the correct use of the PCI DMA API contingent
  * on the Intel IOMMU support (CONFIG_DMAR).
  * Only newer chipsets need to bother with this, of course.
+ *
+ * Xen guests accessing graphics hardware also need proper translation
+ * between pseudo-physical addresses and real machine addresses, which
+ * is also achieved by using the DMA API.
  */
-#ifdef CONFIG_DMAR
+#if defined(CONFIG_DMAR) || defined(CONFIG_XEN)
 #define USE_PCI_DMA_API 1
 #endif
 



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