Re: Failed vm entry with heavy use of emulator

[Razvan Cojocaru <rcojocaru@bitdefender.com>]

On 01/05/2016 01:49 PM, Tamas K Lengyel wrote:
> Hi all,
> I've been stress-testing the built-in emulator using the vm_event
> response VM_EVENT_FLAG_EMULATE feature. In the test I've turned all
> pages non-readable by default and all trapped instructions to be
> emulated. My test code can be found at
> https://github.com/tklengyel/xen/compare/read_emul?expand=1.
> 
> The following crash is reproducible and has been verified by Razvan as well.

Indeed, but I should point out that it only occurs when all the pages
are not readable. For all other cases (restricting write or execute,
that have been heavily tested here) there seem to be no issues,
regardless of how hard we're driving the emulator.

Tamas found this strange (and I agree) since we've assumed that the
emulator doesn't care about EPT restrictions. But our use cases so far
have never blocked page reads.


Cheers,
Razvan