I think the ancillary data for #DB and #PF should be added to kvm_queued_exception and plumbed through to where it's needed. Vector number and error code are not sufficient to describe a #DB or #PF. On Sat, Jul 22, 2017 at 5:29 PM, Wanpeng Li <kernellwp@xxxxxxxxx> wrote: > 2017-07-22 22:25 GMT+08:00 Jim Mattson <jmattson@xxxxxxxxxx>: >> On Fri, Jul 21, 2017 at 1:39 AM, Wanpeng Li <kernellwp@xxxxxxxxx> wrote: >>> Hi Jim, >>> 2017-07-21 3:16 GMT+08:00 Jim Mattson <jmattson@xxxxxxxxxx>: >>>> On Wed, Jul 19, 2017 at 7:31 PM, Wanpeng Li <kernellwp@xxxxxxxxx> wrote: >>>>> Hi Jim, >>>>> 2017-07-19 2:47 GMT+08:00 Jim Mattson <jmattson@xxxxxxxxxx>: >>>>>> Why do we expect the VM_EXIT_INTR_INFO and EXIT_QUALIFICATION fields >>>>>> of the VMCS to have the correct values for the injected exception? >>>>> >>>>> Good point, I think we should synthesize VM_EXIT_INTR_INFO and >>>>> EXIT_QUALIFICATION manually, I will post a patch for it. Btw, how >>>>> about setting EXIT_QULIFICATION to vcpu->arch.cr2 for the page fault >>>>> exception and 0 for other exceptions? >>>> >>>> From the SDM, section 27.1: >>>> >>>> If an event causes a VM exit directly, it does not update >>> >>> I mentioned this in the patch description: >>> >>>> However, there is no guarantee the exit reason is exception currently, when there is an external interrupt occurred on host, maybe a time interrupt for host which should not be injected to guest, and somewhere queues an exception, then the function nested_vmx_check_exception() will be called and the vmexit emulation codes will try to emulate the "Acknowledge interrupt on exit" behavior, the warning is triggered. >>> >>> If you think the scenario is correct, then it should be an event >>> causes a VM exit indirectly. So if both the scenario which I mentioned >>> and "This function >>> assumes it is called with the exit reason in vmcs02 being a #PF >>> exception" can happen, then maybe we should figure out how to fix both >>> scenarios suitable. >> >> In the situation you describe, the #PF causes a synthesized VM-exit >> from L2 to L1 directly, not indirectly. From the SDM: >> >> An exception causes a VM exit directly if the bit corresponding to >> that exception is set in the exception bitmap. >> >> Hence, CR2 should not be set yet. > > Any idea how to synthesize exit qualification for page fault and debug > exception? > > Regards, > Wanpeng Li > >> >>> >>>> architectural state as it would have if it had it not caused the VM >>>> exit: >>>> - A debug exception does not update DR6, DR7.GD, or >>>> IA32_DEBUGCTL.LBR. (Information about the nature of the debug >>>> exception is saved in the exit qualification field.) >>>> - A page fault does not update CR2. (The linear address causing >>>> the page fault is saved in the exit-qualification field.) >>>> >>>> This means that vcpu->arch.cr2 should not be set at this point for a >>>> #PF injection (and vcpu->arch.dr6 should not be set at this point for >>>> a #DB injection). For all other exceptions, yes, the exit >>>> qualification should be cleared. >>>>
