--- arch/x86/kernel/aperture_64.c

+++ arch/x86/kernel/aperture_64.c

@@ -389,6 +389,7 @@ void __init gart_iommu_hole_init(void)

for (i = 0; i < ARRAY_SIZE(bus_dev_ranges); i++) {

int bus;

int dev_base, dev_limit;

+ u32 ctl;

bus = bus_dev_ranges[i].bus;

dev_base = bus_dev_ranges[i].dev_base;

@@ -401,7 +402,19 @@ void __init gart_iommu_hole_init(void)

iommu_detected = 1;

gart_iommu_aperture = 1;

- aper_order = (read_pci_config(bus, slot, 3, AMD64_GARTAPERTURECTL) >> 1) & 7;

+ ctl = read_pci_config(bus, slot, 3,

+ AMD64_GARTAPERTURECTL);

+

+ /*

+ * Before we do anything else disable the GART. It may

+ * still be enabled if we boot into a crash-kernel here.

+ * Reconfiguring the GART while it is enabled could have

+ * unknown side-effects.

+ */

+ ctl &= ~GARTEN;

+ write_pci_config(bus, slot, 3, AMD64_GARTAPERTURECTL, ctl);

+

+ aper_order = (ctl >> 1) & 7;

aper_size = (32 * 1024 * 1024) << aper_order;

aper_base = read_pci_config(bus, slot, 3, AMD64_GARTAPERTUREBASE) & 0x7fff;

aper_base <<= 25;