svn commit: r260666 - head/sys/ia64/ia64

[Marcel Moolenaar]

Author: marcel
Date: Wed Jan 15 03:57:41 2014
New Revision: 260666
URL: http://svnweb.freebsd.org/changeset/base/260666

Log:
  In the nested TLB fault handler, for a direct-mapped address, make
  sure to clear the lower 12 bits. We're adding the translation
  attributes to the physical address and non-zero bits in the first
  12 bits would give us something unexpected, including invalid bit
  values. Those trigger nested general protection faults.
  We do not have to clear the region bits, because they are ignored
  anyway, so we can replace an existing dep instruction with the one
  we need.
  
  This fixes GP faults for the swapper thread, as it's the only thread
  that has a direct-mapped stack. Since the bug is in the nested TLB
  fault handler, the frequency of hitting the GP is in the order of
  hours/days under load.

Modified:
  head/sys/ia64/ia64/exception.S

Modified: head/sys/ia64/ia64/exception.S
==============================================================================
--- head/sys/ia64/ia64/exception.S	Wed Jan 15 01:27:01 2014	(r260665)
+++ head/sys/ia64/ia64/exception.S	Wed Jan 15 03:57:41 2014	(r260666)
@@ -1026,7 +1026,7 @@ IVT_ENTRY(Data_Nested_TLB, 0x1400)
 }
 {	.mii
 	mov		cr.itir=r26
-(p12)	dep		r28=0,r30,61,3
+(p12)	dep		r28=0,r30,0,12
 (p13)	extr.u		r28=r30,3*PAGE_SHIFT-8, PAGE_SHIFT-3	// dir L0 index
 	;;
 }