Re: [Xen-devel] Vmx_vmenter_helper() and hvm_inject_page_fault()

[Razvan Cojocaru <rzvncj@xxxxxxxxx>]

>> OK, let's assume that I need it for debugging purposes. Should the
>> call, assuming that I check for usermode as explained above before
>> calling hvm_inject_page_fault(ec | PFEC_user_mode, address), work as
>> advertised?
>
> I'm not sure, which is why I'd recommend against it. As said, I
> could see you use the usermode check for debugging purposes,
> but I can't see what use injection of a #PF there would have.
>
>> If not, what would be a better place to put this page
>> fault injection assuming I'd like to trigger it at VMENTER time?
>
> You ought to do all this in the context of handling the
> corresponding VMEXIT.

Well, the scenario would be this (bear with me here): there'd be a
hypercall setting up pagefault injection in the HV. This hypercall
would be called from dom0 userspace as part as handing a mem_event.
Now, when the guest gets control again, it would inject a page fault
based on the information previously sent to the HV. The only obvious
place (to me) where this could happen correctly would be somewhere in
the VMENTRY code - it might be too late by the time the next VMEXIT is
reached. So I'm looking for a safe and robust way to do that.

Thanks.

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