On 14/02/18 18:22, Andrew Cooper wrote: > On 14/02/18 16:10, Alexandru Stefan ISAILA wrote: >> On Lu, 2018-02-12 at 15:54 +0000, Andrew Cooper wrote: >>> On 12/02/18 15:08, Alexandru Isaila wrote: >>>> @@ -2619,14 +2634,31 @@ void svm_vmexit_handler(struct >>>> cpu_user_regs *regs) >>>> break; >>>> >>>> case VMEXIT_EXCEPTION_BP: >>>> - if ( !v->domain->debugger_attached ) >>>> - goto unexpected_exit_type; >>>> - /* AMD Vol2, 15.11: INT3, INTO, BOUND intercepts do not >>>> update RIP. */ >>>> - if ( (inst_len = __get_instruction_length(v, INSTR_INT3)) >>>> == 0 ) >>>> + inst_len = __get_instruction_length(v, INSTR_INT3); >>> There are multiple ways of ending up with this vmexit, and INT3 is >>> not >>> the only way. >>> >>> The old code was somewhat broken (but only in the case that a >>> debugger >>> was attached), but now with this introspection hook active, >>> executing >>> `0xcd 0x03` will end up crashing the domain because of a length >>> mismatch >>> looking for 0xcc. >>> >>> You need to inspect EXITINTINFO to work out what went on here, and >>> distinguish INT3 from INT $3. >>> >>> Can I suggest that you run this unit test >>> http://xenbits.xen.org/docs/xtf/test-swint-emulation.html under debug >>> introspection an check that you get all expected events? Every time >>> we >>> touch this code, we seem to break it :( >>> >>> ~Andrew >>> >> I've tested on Intel and AMD and I only get events on int3. Further >> more, I don't think there is any way to use the vmcb->exitintinfo >> because all the fields are 0 on the time of VMEXIT_EXCEPTION_BP. Did I >> understand the test scenario correctly? > Quite possibly, but now I'm even more confused. I'll have a quick play.
Ok - after some investigation, executing `int $3` triggers VMEXIT_SWINT, with the vector in EXITINFO1, as opposed to triggering VMEXIT_EXCP3, except that we don't have INTERCEPT_SWINT active, so it completes internally. Therefore, in your patch, we do expect only ever to find an int3 triggering VMEXIT_EXCEPTION_BP. Sorry for the noise. However, do you mind rebasing the remainder of your series onto staging? It doesn't apply cleanly any more. ~Andrew _______________________________________________ Xen-devel mailing list Xenemail@example.com https://lists.xenproject.org/mailman/listinfo/xen-devel