nixpkgs/pkgs/applications/virtualization/xen/0000-qemu-seabios-enable-ATA_DMA.patch

diff -uNr a/src/Kconfig b/src/Kconfig
--- a/src/Kconfig	2015-08-31 10:15:13.231134858 +0200
+++ b/src/Kconfig	2015-08-31 10:14:24.039180178 +0200
@@ -144,13 +144,13 @@
     config ATA_DMA
         depends on ATA
         bool "ATA DMA"
-        default n
+        default y
         help
             Detect and try to use ATA bus mastering DMA controllers.
     config ATA_PIO32
         depends on ATA
         bool "ATA 32bit PIO"
-        default n
+        default y
         help
             Use 32bit PIO accesses on ATA (minor optimization on PCI transfers).
     config AHCI