2.6.27-stable review patch. If anyone has any objections, please let us know. ------------------ From: Mark Langsdorf commit fe2245c905631a3a353504fc04388ce3dfaf9d9e upstream. 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: 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(-) --- 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 ag memset(gatt, 0, gatt_size); agp_gatt_table = gatt; - enable_gart_translations(); - error = sysdev_class_register(&gart_sysdev_class); if (!error) error = sysdev_register(&device_gart); @@ -828,6 +826,14 @@ void __init gart_iommu_init(void) 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): * Set unmapped entries to a scratch page instead of 0. * Any prefetches that hit unmapped entries won't get an bus abort -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/