Question regarding nested_svm_inject_npf_exit()

[Nadav Amit <nadav.amit@xxxxxxxxx>]

Hello Paolo,

I encountered an issue while running some svm tests. Apparently, the tests
“npt_rw_pfwalk” and “npt_rsv_pfwalk” expect the present bit to be clear.

KVM indeed clears this bit in nested_svm_inject_npf_exit():

       /*
        * The present bit is always zero for page structure faults on real
        * hardware.
        */
       if (svm->vmcb->control.exit_info_1 & (2ULL << 32))
               svm->vmcb->control.exit_info_1 &= ~1;


I could not find documentation of this behavior. Unfortunately, I do not
have a bare-metal AMD machine to test the behavior (and some enabling of
kvm-unit-tests/svm is required, e.g. this test does not run with more than
4GB of memory).

Are you sure that this is the way AMD machines behave?

Thanks,
Nadav