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From: Ed Maste <emaste@FreeBSD.org>
Date: Fri, 2 Mar 2012 00:21:08 +0000 (UTC)
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Subject: svn commit: r232372 - stable/9/sys/x86/x86
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Author: emaste
Date: Fri Mar  2 00:21:07 2012
New Revision: 232372
URL: http://svn.freebsd.org/changeset/base/232372

Log:
  MFC r232267:
    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@.
  
  Sponsored by:   Sandvine Incorporated

Modified:
  stable/9/sys/x86/x86/busdma_machdep.c
Directory Properties:
  stable/9/sys/   (props changed)

Modified: stable/9/sys/x86/x86/busdma_machdep.c
==============================================================================
--- stable/9/sys/x86/x86/busdma_machdep.c	Fri Mar  2 00:15:52 2012	(r232371)
+++ stable/9/sys/x86/x86/busdma_machdep.c	Fri Mar  2 00:21:07 2012	(r232372)
@@ -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;