Re: [RFC PATCH 0/4] Add support for EPT execute only for nested hypervisors

[Bandan Das <bsd@redhat.com>]

Xiao Guangrong <guangrong.xiao@linux.intel.com> writes:

> On 06/21/2016 11:12 AM, Bandan Das wrote:
>> I spoke to Paolo about this a while back and thought to post this as
>> RFC while I am thinking of adding some unit tests.
>>
>> Background: ESX refuses to run as L1 if support for EPT execute only isn't
>> found. I am not really sure if it uses it for anything since just advertising
>> the bits seems to work but adding the necessary plumbing seemed like a good idea.
>>
>> Xiao, I took the liberty of adding you based on "git blame" :)
>
> Thank you, Bandan! I really hope all mmu related patches can be CCed to me
> in case if i am too busy to watch patches in kvm mail list. :)

We all try but it's easy to miss interested people in the cc list :)

> Some points are missed in this patchset:
> 1) You also need to tech is_present_gpte() about this fact.

If I understood right, this isn't needed anymore since a check
for rsvd bits follows and is_present_gpte already does pte & 7.

> 2) update_permission_bitmask() need to be fixed as it always expects
>    that read-access is available (actually, read-access is equal with
>    user-access if ept is shadowed).
Do you mean this part of update_permission_bitmask() ?
...
} else
  	/* Not really needed: no U/S accesses on ept  */
	u = 1;