[PATCH v14 10/44] arm64: RMI: Add support for SRO

[Steven Price]

On 14/05/2026 09:01, Aneesh Kumar K.V wrote:
> Steven Price <steven.price at arm.com> writes:
> 
>> +unsigned long rmi_sro_execute(struct rmi_sro_state *sro, gfp_t gfp)
>> +{
>> +	unsigned long sro_handle;
>> +	struct arm_smccc_1_2_regs regs;
>> +	struct arm_smccc_1_2_regs *regs_in = &sro->regs;
>> +
>> +	rmi_smccc_invoke(regs_in, &regs);
>> +
>> +	sro_handle = regs.a1;
>> +
>> +	while (RMI_RETURN_STATUS(regs.a0) == RMI_INCOMPLETE) {
>> +		bool can_cancel = RMI_RETURN_CAN_CANCEL(regs.a0);
>> +		int ret;
>> +
>> +		switch (RMI_RETURN_MEMREQ(regs.a0)) {
>> +		case RMI_OP_MEM_REQ_NONE:
>> +			regs = (struct arm_smccc_1_2_regs){
>> +				SMC_RMI_OP_CONTINUE, sro_handle, 0
>> +			};
>> +			rmi_smccc_invoke(&regs, &regs);
>> +			break;
>> +		case RMI_OP_MEM_REQ_DONATE:
>> +			ret = rmi_sro_donate(sro, sro_handle, regs.a2, &regs,
>> +					     gfp);
>> +			break;
>> +		case RMI_OP_MEM_REQ_RECLAIM:
>> +			ret = rmi_sro_reclaim(sro, sro_handle, &regs);
>> +			break;
>> +		default:
>> +			ret = WARN_ON(1);
>> +			break;
>> +		}
>> +
>> +		if (ret) {
>> +			if (can_cancel) {
>> +				/*
>> +				 * FIXME: Handle cancelling properly!
>> +				 *
>> +				 * If the operation has failed due to memory
>> +				 * allocation failure then the information on
>> +				 * the memory allocation should be saved, so
>> +				 * that the allocation can be repeated outside
>> +				 * of any context which prevented the
>> +				 * allocation.
>> +				 */
>> +			}
>> +			if (WARN_ON(ret))
>> +				return ret;
>> +		}
>> +	}
>> +
>> +	return regs.a0;
>> +}
> 
> Can you also add support to return x1,x2 etc

Indeed that's going to be needed. Looking at this function again I don't 
think we actually need the on-stack 'regs' any more. So the below (very 
lightly tested) diff would use the regs from sro which also means they 
will be there for the caller if it needs them.

Thanks,
Steve

---8<---
diff --git a/arch/arm64/kernel/rmi.c b/arch/arm64/kernel/rmi.c
index a8107ca9bb6d..58a0216be409 100644
--- a/arch/arm64/kernel/rmi.c
+++ b/arch/arm64/kernel/rmi.c
@@ -356,30 +356,29 @@ void rmi_sro_free(struct rmi_sro_state *sro)
 unsigned long rmi_sro_execute(struct rmi_sro_state *sro, gfp_t gfp)
 {
 	unsigned long sro_handle;
-	struct arm_smccc_1_2_regs regs;
-	struct arm_smccc_1_2_regs *regs_in = &sro->regs;
+	struct arm_smccc_1_2_regs *regs = &sro->regs;
 
-	rmi_smccc_invoke(regs_in, &regs);
+	rmi_smccc_invoke(regs, regs);
 
-	sro_handle = regs.a1;
+	sro_handle = regs->a1;
 
-	while (RMI_RETURN_STATUS(regs.a0) == RMI_INCOMPLETE) {
-		bool can_cancel = RMI_RETURN_CAN_CANCEL(regs.a0);
+	while (RMI_RETURN_STATUS(regs->a0) == RMI_INCOMPLETE) {
+		bool can_cancel = RMI_RETURN_CAN_CANCEL(regs->a0);
 		int ret;
 
-		switch (RMI_RETURN_MEMREQ(regs.a0)) {
+		switch (RMI_RETURN_MEMREQ(regs->a0)) {
 		case RMI_OP_MEM_REQ_NONE:
-			regs = (struct arm_smccc_1_2_regs){
+			*regs = (struct arm_smccc_1_2_regs){
 				SMC_RMI_OP_CONTINUE, sro_handle, 0
 			};
-			rmi_smccc_invoke(&regs, &regs);
+			rmi_smccc_invoke(regs, regs);
 			break;
 		case RMI_OP_MEM_REQ_DONATE:
-			ret = rmi_sro_donate(sro, sro_handle, regs.a2, &regs,
+			ret = rmi_sro_donate(sro, sro_handle, regs->a2, regs,
 					     gfp);
 			break;
 		case RMI_OP_MEM_REQ_RECLAIM:
-			ret = rmi_sro_reclaim(sro, sro_handle, &regs);
+			ret = rmi_sro_reclaim(sro, sro_handle, regs);
 			break;
 		default:
 			ret = WARN_ON(1);
@@ -404,7 +403,7 @@ unsigned long rmi_sro_execute(struct rmi_sro_state *sro, gfp_t gfp)
 		}
 	}
 
-	return regs.a0;
+	return regs->a0;
 }
 
 static int rmi_check_version(void)