Re: [PATCH 1/6] firmware: arm_rmm: Add SMC definitions for calling the RMM

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] `struct rec_exit` contains 4 bytes of implicit compiler padding between `padding9` and `plane`.
- [Low] Discrepancy between the `PROT_MAP` macro prefix and the `DATA_MAP` comment and SMC command name.
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--- Patch [1]: [PATCH 1/6] firmware: arm_rmm: Add SMC definitions for calling the RMM ---
commit c161f24da1669945cb4dc961f3a3c4ef452450b6
Author: Steven Price <steven.price@arm.com>
firmware: arm_rmm: Add SMC definitions for calling the RMM

The RMM (Realm Management Monitor) provides functionality that can be
accessed by SMC calls from the host.

> diff --git a/include/linux/arm-smccc-rmi.h b/include/linux/arm-smccc-rmi.h
> new file mode 100644
> index 0000000000000..c965e8867518f
> --- /dev/null
> +++ b/include/linux/arm-smccc-rmi.h

[ ... ]

> +	union { /* 0x600 */
> +		struct {
> +			u16 imm;
> +			u16 padding9;
> +			u64 plane;

[Severity: Low]
Does this struct layout contain implicit padding? The sequence of two u16
fields followed by a u64 field forces the compiler to inject 4 bytes of
padding to align the plane field to an 8-byte boundary. While deterministic
on ARM64, implicit padding in ABI structures shared with firmware is usually
avoided. Should an explicit 32-bit padding field be added here?

> +		};
> +		u8 padding6[0x100];
> +	};

[ ... ]

> +/* RMI_RTT_DATA_MAP_FLAGS definitions */
> +#define RMI_RTT_PROT_MAP_FLAGS_OADDR_TYPE	GENMASK(1, 0)
> +#define RMI_RTT_PROT_MAP_FLAGS_LIST_COUNT	GENMASK(15, 2)

[Severity: Low]
This isn't a bug, but there seems to be a naming discrepancy. The comment
mentions RMI_RTT_DATA_MAP_FLAGS, which corresponds to the
SMC_RMI_RTT_DATA_MAP command, but the macros are prefixed with
RMI_RTT_PROT_MAP_FLAGS. Should these macros use the DATA_MAP prefix instead?

> +
> +/* S2AP Direct Encodings, used in RMI_RTT_UNPROT_MAP_FLAGS_S2AP */
> +#define RMI_S2AP_DIRECT_WRITE			BIT(0)
> +#define RMI_S2AP_DIRECT_READ			BIT(1)
> +
> +#endif /* __LINUX_ARM_SMCCC_RMI_H_ */

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Sashiko AI review · https://sashiko.dev/#/patchset/20260715142739.80398-1-steven.price@arm.com?part=1