[XEN PATCH] xen/arm: ffa: return FFA_RET_NOT_SUPPORTED on unhandled calls

[Jens Wiklander <jens.wiklander@xxxxxxxxxx>]

Until now has an unsupported FF-A request been reported back with
ARM_SMCCC_ERR_UNKNOWN_FUNCTION in register x0. A FF-A caller would
rather expect FFA_ERROR in x0 and FFA_RET_NOT_SUPPORTED in x2 so update
ffa_handle_call() to return true and with the cpu_user_regs updated.

Fixes: 38846de2176b ("xen/arm: tee: add a primitive FF-A mediator")
Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
---
 xen/arch/arm/tee/ffa.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
index 183528d13388..98905fec7967 100644
--- a/xen/arch/arm/tee/ffa.c
+++ b/xen/arch/arm/tee/ffa.c
@@ -1477,7 +1477,8 @@ static bool ffa_handle_call(struct cpu_user_regs *regs)
 
     default:
         gprintk(XENLOG_ERR, "ffa: unhandled fid 0x%x\n", fid);
-        return false;
+        set_regs_error(regs, FFA_RET_NOT_SUPPORTED);
+        return true;
     }
 }
 
-- 
2.34.1