Re: [PATCH v6 08/10] arm/arm64: Provide a wrapper for SMCCC 1.1 calls

Marc Zyngier
2019-10-21T11:43:10Z

On 2019-10-11 13:59, Steven Price wrote:
> SMCCC 1.1 calls may use either HVC or SMC depending on the PSCI
> conduit. Rather than coding this in every call site provide a macro
> which uses the correct instruction. The macro also handles the case
> where no PSCI conduit is configured returning a not supported error
> in res, along with returning the conduit used for the call.
>
> This allow us to remove some duplicated code and will be useful later
> when adding paravirtualized time hypervisor calls.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> Acked-by: Will Deacon <will@kernel.org>
> ---
> include/linux/arm-smccc.h | 44
> +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 44 insertions(+)
>
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 5daf0e2adf47..fd84a9bfb455 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -303,6 +303,50 @@ asmlinkage void __arm_smccc_hvc(unsigned long
> a0, unsigned long a1,
> #define SMCCC_RET_NOT_SUPPORTED -1
> #define SMCCC_RET_NOT_REQUIRED -2
>
> +/* Like arm_smccc_1_1* but always returns SMCCC_RET_NOT_SUPPORTED.
> + * Used when the PSCI conduit is not defined. The empty asm
> statement
> + * avoids compiler warnings about unused variables.

nit: comment style.

> + */
> +#define __fail_smccc_1_1(...) \
> + do { \
> + __declare_args(__count_args(__VA_ARGS__), __VA_ARGS__); \
> + asm ("" __constraints(__count_args(__VA_ARGS__))); \
> + if (___res) \
> + ___res->a0 = SMCCC_RET_NOT_SUPPORTED; \
> + } while (0)
> +
> +/*
> + * arm_smccc_1_1_invoke() - make an SMCCC v1.1 compliant call
> + *
> + * This is a variadic macro taking one to eight source arguments,
> and
> + * an optional return structure.
> + *
> + * @a0-a7: arguments passed in registers 0 to 7
> + * @res: result values from registers 0 to 3
> + *
> + * This macro will make either an HVC call or an SMC call depending
> on the
> + * current PSCI conduit. If no valid conduit is available then -1
> + * (SMCCC_RET_NOT_SUPPORTED) is returned in @res.a0 (if supplied).
> + *
> + * The return value also provides the conduit that was used.
> + */
> +#define arm_smccc_1_1_invoke(...) ({ \
> + int method = psci_ops.conduit; \
> + switch (method) { \
> + case PSCI_CONDUIT_HVC: \
> + arm_smccc_1_1_hvc(__VA_ARGS__); \
> + break; \
> + case PSCI_CONDUIT_SMC: \
> + arm_smccc_1_1_smc(__VA_ARGS__); \
> + break; \
> + default: \
> + __fail_smccc_1_1(__VA_ARGS__); \
> + method = PSCI_CONDUIT_NONE; \
> + break; \
> + } \
> + method; \
> + })
> +
> /* Paravirtualised time calls (defined by ARM DEN0057A) */
> #define ARM_SMCCC_HV_PV_TIME_FEATURES \
> ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \

All this should most probably go on top of the SMCCC conduit cleanup
that
has already been already queued in the arm64 tree (see
arm64/for-next/smccc-conduit-cleanup).

Thanks,

M.
--
Jazz is not dead. It just smells funny...