Re: [PATCH v4 01/15] arm64: rsi: Add RSI definitions

Gavin Shan
2024-07-23T06:22:57Z

On 7/1/24 7:54 PM, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.com>
>
> The RMM (Realm Management Monitor) provides functionality that can be
> accessed by a realm guest through SMC (Realm Services Interface) calls.
>
> The SMC definitions are based on DEN0137[1] version A-eac5.
>
> [1] https://developer.arm.com/documentation/den0137/latest
>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> Changes since v3:
> * Drop invoke_rsi_fn_smc_with_res() function and call arm_smccc_smc()
> directly instead.
> * Rename header guard in rsi_smc.h to be consistent.
> Changes since v2:
> * Rename rsi_get_version() to rsi_request_version()
> * Fix size/alignment of struct realm_config
> ---
> arch/arm64/include/asm/rsi_cmds.h | 38 ++++++++
> arch/arm64/include/asm/rsi_smc.h | 142 ++++++++++++++++++++++++++++++
> 2 files changed, 180 insertions(+)
> create mode 100644 arch/arm64/include/asm/rsi_cmds.h
> create mode 100644 arch/arm64/include/asm/rsi_smc.h
>

Some nits and questions like below.

> diff --git a/arch/arm64/include/asm/rsi_cmds.h b/arch/arm64/include/asm/rsi_cmds.h
> new file mode 100644
> index 000000000000..89e907f3af0c
> --- /dev/null
> +++ b/arch/arm64/include/asm/rsi_cmds.h
> @@ -0,0 +1,38 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2023 ARM Ltd.
> + */
> +
> +#ifndef __ASM_RSI_CMDS_H
> +#define __ASM_RSI_CMDS_H
> +
> +#include <linux/arm-smccc.h>
> +
> +#include <asm/rsi_smc.h>
> +
> +static inline unsigned long rsi_request_version(unsigned long req,
> + unsigned long *out_lower,
> + unsigned long *out_higher)
> +{
> + struct arm_smccc_res res;
> +
> + arm_smccc_smc(SMC_RSI_ABI_VERSION, req, 0, 0, 0, 0, 0, 0, &res);
> +
> + if (out_lower)
> + *out_lower = res.a1;
> + if (out_higher)
> + *out_higher = res.a2;
> +
> + return res.a0;
> +}
> +
> +static inline unsigned long rsi_get_realm_config(struct realm_config *cfg)
> +{
> + struct arm_smccc_res res;
> +
> + arm_smccc_smc(SMC_RSI_REALM_CONFIG, virt_to_phys(cfg),
> + 0, 0, 0, 0, 0, 0, &res);
> + return res.a0;
> +}
> +
> +#endif

#endif /* __ASM_RSI_CMDS_H */

> diff --git a/arch/arm64/include/asm/rsi_smc.h b/arch/arm64/include/asm/rsi_smc.h
> new file mode 100644
> index 000000000000..b3b3aff88f71
> --- /dev/null
> +++ b/arch/arm64/include/asm/rsi_smc.h
> @@ -0,0 +1,142 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2023 ARM Ltd.
> + */
> +
> +#ifndef __ASM_RSI_SMC_H_
> +#define __ASM_RSI_SMC_H_
> +
> +/*
> + * This file describes the Realm Services Interface (RSI) Application Binary
> + * Interface (ABI) for SMC calls made from within the Realm to the RMM and
> + * serviced by the RMM.
> + */
> +
> +#define SMC_RSI_CALL_BASE 0xC4000000
> +
> +/*
> + * The major version number of the RSI implementation. Increase this whenever
> + * the binary format or semantics of the SMC calls change.
> + */
> +#define RSI_ABI_VERSION_MAJOR 1
> +
> +/*
> + * The minor version number of the RSI implementation. Increase this when
> + * a bug is fixed, or a feature is added without breaking binary compatibility.
> + */
> +#define RSI_ABI_VERSION_MINOR 0
> +
> +#define RSI_ABI_VERSION ((RSI_ABI_VERSION_MAJOR << 16) | \
> + RSI_ABI_VERSION_MINOR)
> +
> +#define RSI_ABI_VERSION_GET_MAJOR(_version) ((_version) >> 16)
> +#define RSI_ABI_VERSION_GET_MINOR(_version) ((_version) & 0xFFFF)
> +
> +#define RSI_SUCCESS 0
> +#define RSI_ERROR_INPUT 1
> +#define RSI_ERROR_STATE 2
> +#define RSI_INCOMPLETE 3
> +

I think these return values are copied from tf-rmm/lib/smc/include/smc-rsi.h, but
UL() prefix has been missed. It's still probably worthy to have it to indicate the
width of the return values. Besides, it seems that RSI_ERROR_COUNT is also missed
here.

> +#define SMC_RSI_FID(_x) (SMC_RSI_CALL_BASE + (_x))
> +
> +#define SMC_RSI_ABI_VERSION SMC_RSI_FID(0x190)
> +
> +/*
> + * arg1 == Challenge value, bytes: 0 - 7
> + * arg2 == Challenge value, bytes: 7 - 15
> + * arg3 == Challenge value, bytes: 16 - 23
> + * arg4 == Challenge value, bytes: 24 - 31
> + * arg5 == Challenge value, bytes: 32 - 39
> + * arg6 == Challenge value, bytes: 40 - 47
> + * arg7 == Challenge value, bytes: 48 - 55
> + * arg8 == Challenge value, bytes: 56 - 63
> + * ret0 == Status / error
> + * ret1 == Upper bound of token size in bytes
> + */
> +#define SMC_RSI_ATTESTATION_TOKEN_INIT SMC_RSI_FID(0x194)
> +

In tf-rmm/lib/smc/include/smc-rsi.h, it is SMC_RSI_ATTEST_TOKEN_INIT instead
of SMC_RSI_ATTESTATION_TOKEN_INIT. The short description for all SMC calls have
been dropped and I think they're worthy to be kept. At least, it helps readers
to understand what the SMC call does. For this particular SMC call, the short
description is something like below:

/*
* Initialize the operation to retrieve an attestation token.
* :
*/

> +/*
> + * arg1 == The IPA of token buffer
> + * arg2 == Offset within the granule of the token buffer
> + * arg3 == Size of the granule buffer
> + * ret0 == Status / error
> + * ret1 == Length of token bytes copied to the granule buffer
> + */
> +#define SMC_RSI_ATTESTATION_TOKEN_CONTINUE SMC_RSI_FID(0x195)
> +

SMC_RSI_ATTEST_TOKEN_CONTINUE as defined in tf-rmm.

> +/*
> + * arg1 == Index, which measurements slot to extend
> + * arg2 == Size of realm measurement in bytes, max 64 bytes
> + * arg3 == Measurement value, bytes: 0 - 7
> + * arg4 == Measurement value, bytes: 7 - 15
> + * arg5 == Measurement value, bytes: 16 - 23
> + * arg6 == Measurement value, bytes: 24 - 31
> + * arg7 == Measurement value, bytes: 32 - 39
> + * arg8 == Measurement value, bytes: 40 - 47
> + * arg9 == Measurement value, bytes: 48 - 55
> + * arg10 == Measurement value, bytes: 56 - 63
> + * ret0 == Status / error
> + */
> +#define SMC_RSI_MEASUREMENT_EXTEND SMC_RSI_FID(0x193)
> +
> +/*
> + * arg1 == Index, which measurements slot to read
> + * ret0 == Status / error
> + * ret1 == Measurement value, bytes: 0 - 7
> + * ret2 == Measurement value, bytes: 7 - 15
> + * ret3 == Measurement value, bytes: 16 - 23
> + * ret4 == Measurement value, bytes: 24 - 31
> + * ret5 == Measurement value, bytes: 32 - 39
> + * ret6 == Measurement value, bytes: 40 - 47
> + * ret7 == Measurement value, bytes: 48 - 55
> + * ret8 == Measurement value, bytes: 56 - 63
> + */
> +#define SMC_RSI_MEASUREMENT_READ SMC_RSI_FID(0x192)
> +

The order of these SMC call definitions are sorted based on their corresponding
function IDs. For example, SMC_RSI_MEASUREMENT_READ would be appearing prior to
SMC_RSI_MEASUREMENT_EXTEND.

> +#ifndef __ASSEMBLY__
> +
> +struct realm_config {
> + union {
> + struct {
> + unsigned long ipa_bits; /* Width of IPA in bits */
> + unsigned long hash_algo; /* Hash algorithm */
> + };
> + u8 pad[0x1000];
> + };
> +} __aligned(0x1000);
> +

This describes the argument to SMC call RSI_REALM_CONFIG and its address needs to
be aligned to 0x1000. Otherwise, RSI_ERROR_INPUT is returned. This maybe worthy
a comment to explain it why we need 0x1000 alignment here.

It seems the only 4KB page size (GRANULE_SIZE) is supported by tf-rmm at present.
The fixed alignment (0x1000) becomes broken if tf-rmm is extended to support
64KB in future. Maybe tf-rmm was designed to work with the minimal page size (4KB).

> +#endif /* __ASSEMBLY__ */
> +
> +/*
> + * arg1 == struct realm_config addr
> + * ret0 == Status / error
> + */
> +#define SMC_RSI_REALM_CONFIG SMC_RSI_FID(0x196)
> +
> +/*
> + * arg1 == Base IPA address of target region
> + * arg2 == Top of the region
> + * arg3 == RIPAS value
> + * arg4 == flags
> + * ret0 == Status / error
> + * ret1 == Top of modified IPA range
> + */
> +#define SMC_RSI_IPA_STATE_SET SMC_RSI_FID(0x197)
> +
> +#define RSI_NO_CHANGE_DESTROYED 0
> +#define RSI_CHANGE_DESTROYED 1
> +
> +/*
> + * arg1 == IPA of target page
> + * ret0 == Status / error
> + * ret1 == RIPAS value
> + */
> +#define SMC_RSI_IPA_STATE_GET SMC_RSI_FID(0x198)
> +
> +/*
> + * arg1 == IPA of host call structure
> + * ret0 == Status / error
> + */
> +#define SMC_RSI_HOST_CALL SMC_RSI_FID(0x199)
> +
> +#endif /* __ASM_RSI_SMC_H_ */

Thanks,
Gavin