x86/gart: Disable GART explicitly before initialization

commit 4b83873d3da0704987cb116833818ed96214ee29 upstream.

If we boot into a crash-kernel the gart might still be
enabled and its caches might be dirty. This can result in
undefined behavior later. Fix it by explicitly disabling the
gart hardware before initialization and flushing the caches
after enablement.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 17 insertions, 1 deletions

diff --git a/arch/x86/kernel/aperture_64.c b/arch/x86/kernel/aperture_64.c
index f147a95fd84a..19f2c703638e 100644
--- a/arch/x86/kernel/aperture_64.c
+++ b/arch/x86/kernel/aperture_64.c
@@ -394,6 +394,7 @@ 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 +408,19 @@ 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;
diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index 34de53b46f87..4f41b29fde98 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -564,6 +564,9 @@ static void enable_gart_translations(void)
 
                 enable_gart_translation(dev, __pa(agp_gatt_table));
         }
+
+        /* Flush the GART-TLB to remove stale entries */
+        k8_flush_garts();
 }
 
 /*