[PATCH v6 1/6] arm64: smccc: Add support for SMCCCv1.2 extended input/output registers

[Mark Rutland]

Hi Sudeep,

On Wed, May 05, 2021 at 10:38:38AM +0100, Sudeep Holla wrote:
> SMCCC v1.2 allows x8-x17 to be used as parameter registers and x4—x17
> to be used as result registers in SMC64/HVC64. Arm Firmware Framework
> for Armv8-A specification makes use of x0-x7 as parameter and result
> registers. There are other users like Hyper-V who intend to use beyond
> x0-x7 as well.
> 
> Current SMCCC interface in the kernel just use x0-x7 as parameter and
> x0-x3 as result registers as required by SMCCCv1.0. Let us add new
> interface to support this extended set of input/output registers namely
> x0-x17 as both parameter and result registers.
> 
> Cc: Michael Kelley <mikelley at microsoft.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc:Catalin Marinas <catalin.marinas at arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>

I have one minor comment below, otherwise this looks good to me, and
regardless:

Acked-by: Mark Rutland <mark.rutland at arm.com>

[...]

> +/**
> + * arm_smccc_1_2_hvc() - make HVC calls
> + * @args: arguments passed via struct arm_smccc_1_2_regs
> + * @res: result values via struct arm_smccc_1_2_regs
> + *
> + * This function is used to make HVC calls following SMC Calling Convention
> + * v1.2 or above. The content of the supplied param are copied from the
> + * structure to registers prior to the HVC instruction. The return values
> + * are updated with the content from registers on return from the HVC
> + * instruction.
> + */
> +asmlinkage void arm_smccc_1_2_hvc(struct arm_smccc_1_2_regs *args,
> +				  struct arm_smccc_1_2_regs *res);
> +
> +/**
> + * arm_smccc_1_2_smc() - make SMC calls
> + * @args: arguments passed via struct arm_smccc_1_2_regs
> + * @res: result values via struct arm_smccc_1_2_regs
> + *
> + * This function is used to make SMC calls following SMC Calling Convention
> + * v1.2 or above. The content of the supplied param are copied from the
> + * structure to registers prior to the SMC instruction. The return values
> + * are updated with the content from registers on return from the SMC
> + * instruction.
> + */
> +asmlinkage void arm_smccc_1_2_smc(struct arm_smccc_1_2_regs *args,
> +				  struct arm_smccc_1_2_regs *res);
> +#endif

It might be worth making the args parameter to these const, since we
never write to it in the asm.

Thanks,
Mark.