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. >>>
