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[Xen-devel] [xen-4.0-testing bisection] complete build-i386-xcpkern

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Subject: [Xen-devel] [xen-4.0-testing bisection] complete build-i386-xcpkern
From: xen.org <ian.jackson@xxxxxxxxxxxxx>
Date: Mon, 29 Nov 2010 22:41:21 +0000
Cc: ian.jackson@xxxxxxxxxxxxx, keir.fraser@xxxxxxxxxxxxx, stefano.stabellini@xxxxxxxxxxxxx
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branch xen-4.0-testing
xen branch xen-4.0-testing
job build-i386-xcpkern
test kernel-build

Tree: http://hg.uk.xensource.com/xen-4.0-testing.hg

*** Found and reproduced problem changeset ***

  Bug is in tree:  http://hg.uk.xensource.com/xen-4.0-testing.hg
  Bug introduced:  2901cbe2eccc
  Bug not present: b6d75c255bf6


  changeset:   21389:2901cbe2eccc
  user:        Keir Fraser <keir@xxxxxxx>
  date:        Mon Nov 29 14:46:01 2010 +0000
  
      x86-64: don't crash Xen upon direct pv guest access to GDT/LDT mapping 
area
      
      handle_gdt_ldt_mapping_fault() is intended to deal with indirect
      accesses (i.e. those caused by descriptor loads) to the GDT/LDT
      mapping area only. While for 32-bit segment limits indeed prevent the
      function being entered for direct accesses (i.e. a #GP fault will be
      raised even before the address translation gets done, on 64-bit even
      user mode accesses would lead to control reaching the BUG_ON() at the
      beginning of that function.
      
      Fortunately the fix is simple: Since the guest kernel runs in ring 3,
      any guest direct access will have the "user mode" bit set, whereas
      descriptor loads always do the translations to access the actual
      descriptors as kernel mode ones.
      
      Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
      
      Further, relax the BUG_ON() in handle_gdt_ldt_mapping_fault() to a
      check-and-bail. This avoids any problems in future, if we don't
      execute x86_64 guest kernels in ring 3 (e.g., because we use a
      lightweight HVM container).
      
      Signed-off-by: Keir Fraser <keir@xxxxxxx>
      xen-unstable changeset:   22448:5cd9612db2bb
      xen-unstable date:        Mon Nov 29 14:34:32 2010 +0000


For bisection revision-tuple graph see:
   
http://www.chiark.greenend.org.uk/~xensrcts/results/bisect.xen-4.0-testing.build-i386-xcpkern.kernel-build.html
Revision IDs in each graph node refer, respectively, to the Trees above.

----------------------------------------
Found failure, as expected, in flight 2860
Host specification list: host=gall-mite
Searching for basis pass: 2780.
(tree in basispass but not in latest: 
http://hg.uk.xensource.com/carbon/trunk/linux-2.6.27.hg)
(tree in basispass but not in latest: 
http://hg.uk.xensource.com/carbon/trunk/linux-2.6.27.pq.hg)
Tree: http://hg.uk.xensource.com/xen-4.0-testing.hg
Latest 465c81b07700
Basis pass b6d75c255bf6
Generating revisions with ./adhoc-revtuple-generator  
http://hg.uk.xensource.com/xen-4.0-testing.hg#b6d75c255bf6-465c81b07700
pulling from http://hg.uk.xensource.com/xen-4.0-testing.hg
searching for changes
no changes found
pulling from http://hg.uk.xensource.com/xen-4.0-testing.hg
searching for changes
no changes found
Loaded 1001 nodes in revision graph
Searching for test results:
 2868 fail 2901cbe2eccc
 2870 fail 2901cbe2eccc
 2780 pass b6d75c255bf6
 2860 fail 465c81b07700
 2865 fail 465c81b07700
 2770 pass b6d75c255bf6
Searching for interesting versions
 0 revisions at b6d75c255bf6
No revisions left to test, checking graph state.

*** Found and reproduced problem changeset ***

  Bug is in tree:  http://hg.uk.xensource.com/xen-4.0-testing.hg
  Bug introduced:  2901cbe2eccc
  Bug not present: b6d75c255bf6


  changeset:   21389:2901cbe2eccc
  user:        Keir Fraser <keir@xxxxxxx>
  date:        Mon Nov 29 14:46:01 2010 +0000
  
      x86-64: don't crash Xen upon direct pv guest access to GDT/LDT mapping 
area
      
      handle_gdt_ldt_mapping_fault() is intended to deal with indirect
      accesses (i.e. those caused by descriptor loads) to the GDT/LDT
      mapping area only. While for 32-bit segment limits indeed prevent the
      function being entered for direct accesses (i.e. a #GP fault will be
      raised even before the address translation gets done, on 64-bit even
      user mode accesses would lead to control reaching the BUG_ON() at the
      beginning of that function.
      
      Fortunately the fix is simple: Since the guest kernel runs in ring 3,
      any guest direct access will have the "user mode" bit set, whereas
      descriptor loads always do the translations to access the actual
      descriptors as kernel mode ones.
      
      Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
      
      Further, relax the BUG_ON() in handle_gdt_ldt_mapping_fault() to a
      check-and-bail. This avoids any problems in future, if we don't
      execute x86_64 guest kernels in ring 3 (e.g., because we use a
      lightweight HVM container).
      
      Signed-off-by: Keir Fraser <keir@xxxxxxx>
      xen-unstable changeset:   22448:5cd9612db2bb
      xen-unstable date:        Mon Nov 29 14:34:32 2010 +0000

Revision graph left in 
/home/xc_osstest/results/bisect.xen-4.0-testing.build-i386-xcpkern.kernel-build.{dot,ps,png,html}.
----------------------------------------
2870: ALL FAIL

flight 2870 xen-4.0-testing real-bisect [real]
http://www.chiark.greenend.org.uk/~xensrcts/logs/2870/

tests which did not succeed:
 build-i386-xcpkern            4 kernel-build                 fail

version targeted for testing:
baseline version:

jobs:
 build-i386-xcpkern           fail     

-------------------------------------------------------------------------------
build-i386-xcpkern:
 1 hosts-allocate               pass     
 2 host-install(2)              pass     
 3 host-build-prep              pass     
 4 kernel-build                 fail     
 xen             21389:2901cbe2eccc

------------------------------------------------------------
sg-report-flight on woking.cam.xci-test.com
logs: /home/xc_osstest/logs
images: /home/xc_osstest/images

Logs, config files, etc. are available at
    http://www.chiark.greenend.org.uk/~xensrcts/logs

Test harness code can be found at
    http://xenbits.xensource.com/gitweb?p=osstest.git;a=summary


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