"enable /disable the CPUs so that only one runs at a time"
Hi Steve,
could you explain if there is already a way to do this in SE mode, or
is it something that we have to hack in?
Thanks.
----- Original Message -----
From: "Steve Reinhardt" <[email protected]>
To: "M5 users mailing list" <[email protected]>
Sent: Tuesday, July 20, 2010 11:33 AM
Subject: Re: [m5-users] changing workloads
On Mon, Jul 19, 2010 at 10:24 PM, nathan binkert <[email protected]> wrote:
I am working on some timing attack problems. I was wondering whether it
is
possible to use m5 in SE mode to do a pseudo switch of contexts: to
execute
a workload, then (using the current processor state including caches,
bpreds
etc) switch to another one - to simulate a regular and an attacker
process.
One possible solution would be switching the same CPU class but with a
different workload parameter. Will it preserve the processor state?
Essentially all that is required is two different address spaces, one for
each workload and the workloads executed sequentially (being able to
schedule between them would be great too!). Perhaps using SMT mode but
suspending / resuming the threads will work for that?
SE mode isn't designed to do this stuff, but that said, I'd imagine
that it could be made to work without too much work. You can't just
switch the workload parameter because the workload is really only used
when the application is starting up. You'd need to have two workloads
loaded into two contexts and write some code to swap contexts.
I can think of a few ways to do it:
- use the SMT support in O3 and enable/disable threads so that only
one runs at a time
- hook up two CPUs to the same caches and enable/disable the CPUs so
that only one runs at a time
- write code to explicitly save/restore the CPU state
The last one is the closest to what happens in real life but also the most
work.
Steve
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