On Fri, 17 Jul 2026 at 11:08, Alex Bennée <[email protected]> wrote: > > Philippe Mathieu-Daudé <[email protected]> writes: > > > On 18/3/26 05:40, Jim Shu wrote: > >> On Tue, Feb 10, 2026 at 8:25 AM Richard Henderson > >> <[email protected]> wrote: > >> ... > >>> Hmm. This really overlaps the secure and space fields from arm, and > >>> possibly some of the > >>> others as well (e.g. user, requester_id, pid). > >>> > >>> I don't really have a good suggestion for that right now, but it would be > >>> nice to not keep > >>> expanding the count of these sorts of fields that somehow specify the > >>> originator, but > >>> clearly cannot overlap. > >>> > >>> I'm reasonably sure we've had this discussion before, but nothing has > >>> come of it. > >>> > >>> Time to paint the bikeshed again? > > > > Last discussion IIRC: > > https://lore.kernel.org/qemu-devel/CAFEAcA8vKNkfKgp_Yymo9NA1=e2xjyxamtgo3z6q6dhgqka...@mail.gmail.com/ > > > > (see also a suggestion in > > https://lore.kernel.org/qemu-devel/[email protected]/) > > Also somewhat related: > > Message-Id: <[email protected]> > Date: Fri, 11 Nov 2022 18:25:15 +0000 > Subject: [PATCH for 8.0 v5 00/20] use MemTxAttrs to avoid current_cpu in hw/ > > Another case that was mentioned in a Core Collective meeting was > handling MMIO devices with IOMMUs (currently requester_id is tied to > PCI). I guess the WorldGuard WID field is a similar thing.
The worldguard ID is more like the Arm security space field, as I understand it -- it encodes what the request should or should not be able to access, and multiple different transaction masters might be able to send with the same worldguard ID. A requester_id on the other hand is intended to identify a unique sender. (In AXI these things turn up in different signals.) I think the trick with requester_id is that we need to identify what we need to encode here and make sure we don't confuse things. (e.g. a CPU needs to not be able to emit something that looks like a PCI request by accident, because some devices need to be able to tell "this really did come from a PCI device" from "this is a CPU doing a normal load/store insn"). So we probably want some kind of "this is what the requester_id is" enum rather than just a convention. thanks -- PMM
