1 files changed, 14 insertions, 2 deletions

diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
index f147a95fd84a..b5d8b0bcf235 100644
--- a/arch/x86/kernel/aperture_64.c
+++ b/arch/x86/kernel/aperture_64.c
@@ -31,7 +31,6 @@
 #include <asm/x86_init.h>
 
 int gart_iommu_aperture;
-EXPORT_SYMBOL_GPL(gart_iommu_aperture);
 int gart_iommu_aperture_disabled __initdata;
 int gart_iommu_aperture_allowed __initdata;
 
@@ -394,6 +393,7 @@ 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;
@@ -407,7 +407,19 @@ void __init gart_iommu_hole_init(void)
                         gart_iommu_aperture = 1;
                         x86_init.iommu.iommu_init = gart_iommu_init;
 
-                        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;