Author: emaste
Date: Tue Feb 28 19:42:40 2012
New Revision: 232267
URL: http://svn.freebsd.org/changeset/base/232267
Log:
Workaround for PCIe 4GB boundary issue
Enforce a boundary of no more than 4GB - transfers crossing a 4GB
boundary can lead to data corruption due to PCIe limitations. This
change is a less-intrusive workaround that can be quickly merged back
to older branches; a cleaner implementation will arrive in HEAD later
but may require KPI changes.
This change is based on a suggestion by jhb@.
Reviewed by: scottl, jhb
Sponsored by: Sandvine Incorporated
MFC after: 3 days
Modified:
head/sys/x86/x86/busdma_machdep.c
Modified: head/sys/x86/x86/busdma_machdep.c
==============================================================================
--- head/sys/x86/x86/busdma_machdep.c Tue Feb 28 19:39:54 2012
(r232266)
+++ head/sys/x86/x86/busdma_machdep.c Tue Feb 28 19:42:40 2012
(r232267)
@@ -227,6 +227,14 @@ bus_dma_tag_create(bus_dma_tag_t parent,
bus_dma_tag_t newtag;
int error = 0;
+ /* Always enforce at least a 4GB (2GB for PAE) boundary. */
+#if defined(__amd64__)
+ if (boundary == 0 || boundary > ((bus_addr_t)1 << 32))
+ boundary = (bus_size_t)1 << 32;
+#elif defined(PAE)
+ if (boundary == 0 || boundary > ((bus_addr_t)1 << 31))
+ boundary = (bus_size_t)1 << 31;
+#endif
/* Basic sanity checking */
if (boundary != 0 && boundary < maxsegsz)
maxsegsz = boundary;
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