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>
diff --git a/arch/x86/kernel/pci-gart_64.c b/arch/x86/kernel/pci-gart_64.c
index f505c38..f20c20a 100644
--- a/arch/x86/kernel/pci-gart_64.c
+++ b/arch/x86/kernel/pci-gart_64.c
@@ -824,10 +824,10 @@
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)