pci-gart_64.c: could we get better explanation?

Add better explanation to pci-gart.

Signed-off-by: Pavel Machek <pavel@suse.cz>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Trivial patch monkey <trivial@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index f505c3890358..f20c20a7853d 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -824,10 +824,10 @@ void __init gart_iommu_init(void)
         wbinvd();
 
         /*
-         * Try to workaround a bug (thanks to BenH)
+         * 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
-         * then.
+         * then. (P2P bridge may be prefetching on DMA reads).
          */
         scratch = get_zeroed_page(GFP_KERNEL);
         if (!scratch)