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Re: [PATCH v2 5/5] xen/arm: Rewrite arm_smccc_*() to return by value
- To: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Date: Fri, 4 Sep 2026 19:20:08 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Jan Setje-Eilers <Jan.SetjeEilers@xxxxxxxxxx>
- Delivery-date: Fri, 04 Sep 2026 18:20:36 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04/09/2026 1:13 pm, Bertrand Marquis wrote:
> Hi Andrew,
>
>> On 4 Sep 2026, at 13:12, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
>>
>> diff --git a/xen/arch/arm/include/asm/smccc.h
>> b/xen/arch/arm/include/asm/smccc.h
>> index 4ed2a40ed0ac..2d0f2db0b256 100644
>> --- a/xen/arch/arm/include/asm/smccc.h
>> +++ b/xen/arch/arm/include/asm/smccc.h
>> @@ -181,21 +174,20 @@ struct arm_smccc_res {
>> * makes it stick.
>> */
>> #define arm_smccc_1_1_smc(...) \
> The comment would need fixing on top of this as current
> one still describes the optional @res argument while now
> we only take a0 to a7 as arguments and return the structure
> instead.
Are you happy with this delta?
diff --git a/xen/arch/arm/include/asm/smccc.h
b/xen/arch/arm/include/asm/smccc.h
index 2d0f2db0b256..c7763acd7f7d 100644
--- a/xen/arch/arm/include/asm/smccc.h
+++ b/xen/arch/arm/include/asm/smccc.h
@@ -159,15 +159,14 @@ struct arm_smccc_res {
* arm_smccc_1_1_smc() - make an SMCCC v1.1 compliant SMC call
*
* This is a variadic macro taking one to eight source arguments, and
- * an optional return structure.
+ * returns four values.
*
* @a0-a7: arguments passed in registers 0 to 7
* @res: result values from registers 0 to 3
*
* This macro is used to make SMC calls following SMC Calling
Convention v1.1.
* The content of the supplied param are copied to registers 0 to 7 prior
- * to the SMC instruction. The return values are updated with the content
- * from register 0 to 3 on return from the SMC instruction if not NULL.
+ * to the SMC instruction.
*
* We have an output list that is not necessarily used, and GCC feels
* entitled to optimise the whole sequence away. "volatile" is what
The overall comment now reads:
/*
* arm_smccc_1_1_smc() - make an SMCCC v1.1 compliant SMC call
*
* This is a variadic macro taking one to eight source arguments, and
* returns four values.
*
* @a0-a7: arguments passed in registers 0 to 7
* @res: result values from registers 0 to 3
*
* This macro is used to make SMC calls following SMC Calling Convention
v1.1.
* The content of the supplied param are copied to registers 0 to 7 prior
* to the SMC instruction.
*
* We have an output list that is not necessarily used, and GCC feels
* entitled to optimise the whole sequence away. "volatile" is what
* makes it stick.
*/
~Andrew
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