Re: [PATCH] KVM: arm64: Forward FFA_NOTIFICATION* calls to TrustZone

[Will Deacon]

On Fri, May 08, 2026 at 01:04:27PM +0000, Sebastian Ene wrote:
> While at it I discovered that none of the FF-A calls in the proxy
> currently check for these SBZ registers. Would you be ok with a diff that
> fixes this before the patch with the notifications ?

I'd probably structure it as a separate patch per call, tbh. That way,
the commit message can talk about the specific fields that are reserved
for a given call. See below.

> Refactor the handling logic in pKVM FF-A proxy to support checking for
> SBZ/MBZ values. While at it, drop the do_ffa_mem_xfer macro and replace
> it with two functions that make it clear that we re-write the
> function-id with a 64-bit variant, to keep the same behavior as before.
> Keep each handler in an array of structures together with a mask that
> corresponds to the SBZ registers the spec expects.

Although I agree that we should be enforcing SBZ/MBZ paramaters (because
we have no idea what they might do in future versions of the spec), I
also think that doing this at the register level is too coarse.

For example, the VM ID parameter to FFA_NOTIFICATION_BITMAP_CREATE has bits
31:16 as MBZ. So I think we probably need to do the checking on a
per-function basis, like Per is doing in his series:

https://lore.kernel.org/r/20260501-host-direct-messages-v6-0-3f4af727ed85@xxxxxxxxxx

Will