Re: [Xen-devel] Xen 4.6.1 crash with altp2m enabled by default

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.08.16 at 17:08, <Kevin.Mayer@xxxxxxxx> wrote:
> crash> x /130x 0xffff830bd0da1000
> 0xffff830bd0da1000:     0x000000000000000e      0x0000000000000000
> 0xffff830bd0da1010:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1020:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1030:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1040:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1050:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1060:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1070:     0x0000000000000000      0x0000000bd0da3000
> 0xffff830bd0da1080:     0x0000000c17e36000      0x0000000000000000
> 0xffff830bd0da1090:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da10a0:     0x00000000e7512000      0x00000000e7513000
> 0xffff830bd0da10b0:     0x0000000bd0da0000      0x0000000000000000
> 0xffff830bd0da10c0:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da10d0:     0x0000000000000000      0x0000006fedea809b
> 0xffff830bd0da10e0:     0x00000001a379e000      0x0000000610f9101e
> 0xffff830bd0da10f0:     0x0000000000000000      0xffffffffffffffff
> 0xffff830bd0da1100:     0x0000000000000000      0x0007010600070106
> 0xffff830bd0da1110:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1120:     0x0000006bb6a075fa      0x000600420000003f
> 0xffff830bd0da1130:     0x0000000000000000      0x000fefff00000000
> 0xffff830bd0da1140:     0x0000000000000000      0x00000000000051ff
> 0xffff830bd0da1150:     0x0000000000000041      0x0000000000000000
> 0xffff830bd0da1160:     0x0000000000000000      0x0000000c00000000
> 0xffff830bd0da1170:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1180:     0x0000000000000001      0x0000000000000000
> 0xffff830bd0da1190:     0x0000000800000000      0x0000000000000000
> 0xffff830bd0da11a0:     0x0000000000000001      0x0000000000000096
> 0xffff830bd0da11b0:     0xffff82d0802bc208      0x00000000806f6dbc
> 0xffff830bd0da11c0:     0x0000000000000000      0x0000000000000400
> 0xffff830bd0da11d0:     0x0000000080550f34      0x00000000f0e48161
> 0xffff830bd0da11e0:     0x0000000000000246      0x0000000000000000
> 0xffff830bd0da11f0:     0x00000000f79c3000      0x00000000804de6f0
> 0xffff830bd0da1200:     0x0000000000000023      0x0000000000000000
> 0xffff830bd0da1210:     0x00c0f300ffffffff      0x0000000000000008
> 0xffff830bd0da1220:     0x0000000000000000      0x00c09b00ffffffff
> 0xffff830bd0da1230:     0x0000000000000010      0x0000000000000000
> 0xffff830bd0da1240:     0x00c09300ffffffff      0x0000000000000023
> 0xffff830bd0da1250:     0x0000000000000000      0x00c0f300ffffffff
> 0xffff830bd0da1260:     0x0000000000000030      0x00000000ffdff000
> 0xffff830bd0da1270:     0x00c0930000001fff      0x0000000000000000
> 0xffff830bd0da1280:     0x0000000000000000      0x01c00000ffffffff
> 0xffff830bd0da1290:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da12a0:     0x01c00000ffffffff      0x0000000000000028
> 0xffff830bd0da12b0:     0x0000000080042000      0x00008b00000020ab
> 0xffff830bd0da12c0:     0x000000008003f000      0x000000008003f400
> 0xffff830bd0da12d0:     0x000007ff000003ff      0x000000008001003b
> 0xffff830bd0da12e0:     0x0000000000039000      0x00000000000026d9
> 0xffff830bd0da12f0:     0x000000000000dc3c      0x0000000000000000
> 0xffff830bd0da1300:     0x0000e00800000000      0x0000000000000000
> 0xffff830bd0da1310:     0x0000000000000000      0x000000000000e040
> 0xffff830bd0da1320:     0x0000050100070406      0x0000000000000000
> 0xffff830bd0da1330:     0x0000000000000000      0x0000000080050033
> 0xffff830bd0da1340:     0x00000001bd665000      0x00000000000026e0
> 0xffff830bd0da1350:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1360:     0xffff830c17e38c80      0xffff830617fd3000
> 0xffff830bd0da1370:     0xffff830617fcf000      0xffff830617fd7fc0
> 0xffff830bd0da1380:     0xffff82d08024e150      0xffff830617fd7f90
> 0xffff830bd0da1390:     0xffff82d080201bb0      0x000000000000e008
> 0xffff830bd0da13a0:     0x0000006000000000      0x0000000000000000
> 0xffff830bd0da13b0:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da13c0:     0xffffffffffffffff      0xffffffffffffffff
> 0xffff830bd0da13d0:     0x000000008001003b      0x00000000000006d9
> 0xffff830bd0da13e0:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da13f0:     0x0000000000000000      0x0000000000000000
> 0xffff830bd0da1400:     0x0000000000000000      0x0000000000000000
> 
> I don't quite understand the Intel developer manual at this point. How do I 
> have to read this data?

I don't think this is formally specified anywhere (publicly). After all that's
why one has to use vmread/vmwrite. 

> Since if ( !(v->arch.hvm_vmx.host_cr0 & X86_CR0_TS) ) must be true I assume 
> the 
> __vmwrite tries to | 0x8 into the host_cr0 leading to the 0x0000000080050033 
> for the current host_cr0 ( or better the 0x80050033 ).

Well, together with the disassembly it should be possible without
consulting the crash dump to tell what value it was that was
attempted to be written (the disassembly tells you which register
and the state dumped to the log tells you the value). If it is (as
you indicated earlier up) indeed zero that gets written, then
you'd want to try to find out where that zero is coming from.

Jan

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