On 06/25/2011 10:44 AM, Yang, Wei Y wrote:
>
>>
>>> +void set_cr4_smep(int smep)
>>> +{
>>> + unsigned long cr4 = read_cr4();
>>> +
>>> + cr4 &= ~CR4_SMEP_MASK;
>>> + if (smep)
>>> + cr4 |= CR4_SMEP_MASK;
>>> + write_cr4(cr4);
>>> +}
>>> +
>>
>> It can work if the box does not support SMEP?
>
> It will report unhandled exception 13 in access.out which
> we count as errors either. Do we need verify it before
> running the smep test case?
>
It can generate the wrong report that is not caused by the fault of KVM,
we'd better avoid it.
>>
>>> void set_efer_nx(int nx)
>>> {
>>> unsigned long long efer;
>>> @@ -176,7 +188,7 @@ void ac_test_init(ac_test_t *at, void *virt)
>>>
>>> int ac_test_bump_one(ac_test_t *at)
>>> {
>>> - for (int i = 0; i < NR_AC_FLAGS; ++i)
>>> + for (int i = 0; i < NR_AC_FLAGS-1; ++i)
>>
>> Why not test "SMEP" for all test case?
>
> It's actually the last question. :)
> The page where the current code stays is user page.
> If enabled SMEP, we must add some code to convert the current page
> into kernel page, or the page fault will occur again and again. And it seems
> no need to test SMEP for all test case. We just need fetch access which we
> do in a separate case.
>
Oh, i see, thanks for your explanation, i think we'd better test SMEP for
all kinds of access, but i don't have strong opinion :-)
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