From fe2245c905631a3a353504fc04388ce3dfaf9d9e Mon Sep 17 00:00:00 2001 From: Mark Langsdorf Date: Sun, 5 Jul 2009 15:50:52 -0500 Subject: [PATCH] x86: enable GART-IOMMU only after setting up protection methods The current code to set up the GART as an IOMMU enables GART translations before it removes the aperture from the kernel memory map, sets the GART PTEs to UC, sets up the guard and scratch pages, or does a wbinvd(). This leaves the possibility of cache aliasing open and can cause system crashes. Re-order the code so as to enable the GART translations only after all safeguards are in place and the tlb has been flushed. AMD has tested this patch on both Istanbul systems and 1st generation Opteron systems with APG enabled and seen no adverse effects. Istanbul systems with HT Assist enabled sometimes see MCE errors due to cache artifacts with the unmodified code. Signed-off-by: Mark Langsdorf Cc: Cc: Joerg Roedel Cc: akpm@linux-foundation.org Cc: jbarnes@virtuousgeek.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/pci-gart_64.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c index 1e8920d98f7c..cfd9f9063896 100644 --- a/arch/x86/kernel/pci-gart_64.c +++ b/arch/x86/kernel/pci-gart_64.c @@ -658,8 +658,6 @@ static __init int init_k8_gatt(struct agp_kern_info *info) agp_gatt_table = gatt; - enable_gart_translations(); - error = sysdev_class_register(&gart_sysdev_class); if (!error) error = sysdev_register(&device_gart); @@ -816,6 +814,14 @@ void __init gart_iommu_init(void) * the pages as Not-Present: */ wbinvd(); + + /* + * Now all caches are flushed and we can safely enable + * GART hardware. Doing it early leaves the possibility + * of stale cache entries that can lead to GART PTE + * errors. + */ + enable_gart_translations(); /* * Try to workaround a bug (thanks to BenH):