Re: PMP shared permissions for S and U
Manuel Offenberg <manuel.a.offenberg@...>
FYI. SPMP TG is awaiting final approval from Technical Steering Commitee.
From: tech-privileged@... <tech-privileged@...> on behalf of Jeff Scott <jeff.scott@...>
Sent: Monday, August 22, 2022 10:02 AM
To: Greg Favor <gfavor@...>
Cc: tech-privileged@... <tech-privileged@...>
Subject: Re: [RISC-V] [tech-privileged] PMP shared permissions for S and U
In our world we don’t have MMU, just PMP. The inability to supply separate permissions to S and U limits the usefulness of PMP in our environment.
I subscribed to SPMP now. I’ll send my question to that email list as well.
From: Greg Favor <gfavor@...>
Caution: EXT Email
PMP was architected to be a mechanism to protect M-mode software and resources from non-M-mode software and devices. This complements the MMU which serves to protect and isolate between S-mode and U-mode (and between U-mode processes). They are intended to be orthogonal and composable architectural components.
If you are looking for something that combines those two functions into one mechanism, then take a look at the new SPMP TG that is in the process of being formed as we speak. I'm not certain, but I think that might be what you are looking for. (Start of group meetings, etc. will be announced on relevant RVI email lists - including the Security HC's list since I believe this TG is being sponsored by that HC.)
On Mon, Aug 22, 2022 at 9:44 AM Jeff Scott <jeff.scott@...> wrote: