Re: [PATCH] exec: Add RISC-V WorldGuard WID field to MemTxAttrs

On Fri, Jul 17, 2026 at 4:59 PM Peter Maydell <[email protected]> wrote:
>
> On Thu, 16 Jul 2026 at 04:12, Jim Shu <[email protected]> wrote:
> >

> >
> > Thanks for mentioning it! I think re-use requester_id is better.
> > Then, I think we only need a boolean flag `src_is_cpu` and we can
> > rename it to `requester_is_cpu` to match the naming of `requester_id`.
>
> But, what do you now want it for? If we put the world ID in the
> MemTxAttrs, do you still need a CPU ID? (There are some situations
> where it might be useful, but if we don't need it right now we
> shouldn't put doing that rework in the path of implementing
> the worldguard work you want to do.)

Yes, Adding the world ID to MemTxAttrs is totally enough for me and
the worldguard patch series.
I just explain the idea if someone still wants to use CPU ID.
Sorry for the confusion.
I will try to add a field that combines ARM secure/space and RISC-V
World ID bits in the next series.

> > > > > The whole plan is to add the following 2 fields
> > > > > ::
> > > > >     unsigned int src_is_cpu:1;
> > > > >     uint16_t src_cpu_id;
> > > > >
> > > > > src_cpu_id is the CPU ID from 'CPUState->cpu_index'. src_is_cpu is a boolean flag to check if the transaction is from CPU.
> > > > >
> > > > > Moreover, I think this idea is extensible. DMA device transactions can also have security attributes like world_id. We can also add src_device field to 'MemTxAttr' to store the 'DeviceState *', so we can get the DeviceState from MemTxAttr to get security attributes. If 'DeviceState *' is too large to add to 'MemTxAttr', re-use requester_id as DMA device ID is another possible method to support this.
> > > >
> > > > I don't think that having the thing that receives the memory
> > > > transaction get or get hold of a pointer to the source of the
> > > > transaction that it then uses to get the world ID is a good idea.
> > > > (Especially not putting a DeviceState* into MemTxAttrs: the
> > > > size of the type needs to be kept small so we can conveniently
> > > > pass it around by value: we currently assert that it is 8 bytes.)
> >
> > OK, I think store the DMA device ID in the `requester_id` is another
> > way to keep the small size.
> > However, IIUC, the current SysbusDevice doesn't have the concept of a
> > device ID. We need to add an additional device ID to the device to
> > support this idea.
>
> What exactly is it that you need a device ID for? Earlier you
> suggest that you would want it to get the world ID -- but we
> should just put the world ID directly in the MemTxAttrs.

Same as previous responce. Adding the world ID is enough for me.
Sorry for the confusion.


Thanks,
Jim