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Re: [Xen-devel] [xen-unstable bisection] complete build-i386-xcpkern



>>> On 30.11.10 at 08:12, Keir Fraser <keir@xxxxxxx> wrote:
> Looks like cause of failure was in the kernel build. So this bisection
> result doesn't look very likely?

If it failed in a guest running on the new hypervisor, this might still
indicate a problem with the change, but the log doesn't provide
any helpful detail (it's the "hg clone" of a 2.6.27 tree that causes
a Python exception, but that can't be connected to the c/s in
question without further information).

Jan

> On 29/11/2010 23:25, "xen.org" <ian.jackson@xxxxxxxxxxxxx> wrote:
> 
>> branch xen-unstable
>> xen branch xen-unstable
>> job build-i386-xcpkern
>> test kernel-build
>> 
>> Tree: http://hg.uk.xensource.com/xen-unstable.hg 
>> 
>> *** Found and reproduced problem changeset ***
>> 
>>   Bug is in tree:  http://hg.uk.xensource.com/xen-unstable.hg 
>>   Bug introduced:  5cd9612db2bb
>>   Bug not present: aba70e59a90d
>> 
>> 
>>   changeset:   22448:5cd9612db2bb
>>   user:        Keir Fraser <keir@xxxxxxx>
>>   date:        Mon Nov 29 14:34:32 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>
>> 
>> 
>> For bisection revision-tuple graph see:
>>    
>> http://www.chiark.greenend.org.uk/~xensrcts/results/bisect.xen-unstable.build-
>>  
>> i386-xcpkern.kernel-build.html
>> Revision IDs in each graph node refer, respectively, to the Trees above.
>> 
>> ----------------------------------------
>> Found failure, as expected, in flight 2861
>> Host specification list: host=gall-mite
>> Searching for basis pass: 2856.
>> (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-unstable.hg 
>> Latest 3afb5ecbf69f
>> Basis pass aba70e59a90d
>> Generating revisions with ./adhoc-revtuple-generator
>> http://hg.uk.xensource.com/xen-unstable.hg#aba70e59a90d-3afb5ecbf69f 
>> pulling from http://hg.uk.xensource.com/xen-unstable.hg 
>> searching for changes
>> no changes found
>> pulling from http://hg.uk.xensource.com/xen-unstable.hg 
>> searching for changes
>> no changes found
>> Loaded 1000 nodes in revision graph
>> Searching for test results:
>>  2853 pass aba70e59a90d
>>  2854 pass aba70e59a90d
>>  2871 fail 3afb5ecbf69f
>>  2872 fail 5cd9612db2bb
>>  2873 fail 5cd9612db2bb
>>  2855 pass aba70e59a90d
>>  2849 pass aba70e59a90d
>>  2861 fail 3afb5ecbf69f
>>  2850 pass irrelevant
>>  2856 pass aba70e59a90d
>> Searching for interesting versions
>>  0 revisions at aba70e59a90d
>> No revisions left to test, checking graph state.
>> 
>> *** Found and reproduced problem changeset ***
>> 
>>   Bug is in tree:  http://hg.uk.xensource.com/xen-unstable.hg 
>>   Bug introduced:  5cd9612db2bb
>>   Bug not present: aba70e59a90d
>> 
>> 
>>   changeset:   22448:5cd9612db2bb
>>   user:        Keir Fraser <keir@xxxxxxx>
>>   date:        Mon Nov 29 14:34:32 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>
>> 
>> Revision graph left in
>> /home/xc_osstest/results/bisect.xen-unstable.build-i386-xcpkern.kernel-build.{
>> dot,ps,png,html}.
>> ----------------------------------------
>> 2873: ALL FAIL
>> 
>> flight 2873 xen-unstable real-bisect [real]
>> http://www.chiark.greenend.org.uk/~xensrcts/logs/2873/ 
>> 
>> 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             22448:5cd9612db2bb
>> 
>> ------------------------------------------------------------
>> 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 
>> 
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx 
>> http://lists.xensource.com/xen-devel 
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx 
> http://lists.xensource.com/xen-devel 



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