linux-kernel - Re: [PATCH v6 01/11] arm64: rsi: Add RSI definitions

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Message-ID: <2ed92455-b97f-40ba-b5d6-695e885be62f@redhat.com>
Date: Tue, 8 Oct 2024 09:08:18 +1000
From: Gavin Shan <gshan@...hat.com>
To: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
 kvmarm@...ts.linux.dev
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
 Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Joey Gouly <joey.gouly@....com>, Alexandru Elisei
 <alexandru.elisei@....com>, Christoffer Dall <christoffer.dall@....com>,
 Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Alper Gun
 <alpergun@...gle.com>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
 Gavin Shan <gshan@...ht.com>
Subject: Re: [PATCH v6 01/11] arm64: rsi: Add RSI definitions

On 10/5/24 12:42 AM, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@....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 1.0-rel0.
> 
> [1] https://developer.arm.com/documentation/den0137/1-0rel0/
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Acked-by: Catalin Marinas <catalin.marinas@....com>
> Reviewed-by: Gavin Shan <gshan@...ht.com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---

[...]

> +
> +static inline unsigned long rsi_set_addr_range_state(phys_addr_t start,
> +						     phys_addr_t end,
> +						     enum ripas state,
> +						     unsigned long flags,
> +						     phys_addr_t *top)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_smc(SMC_RSI_IPA_STATE_SET, start, end, state,
> +		      flags, 0, 0, 0, &res);
> +
> +	if (top)
> +		*top = res.a1;
> +
> +	if (res.a2 != RSI_ACCEPT)
> +		return -EPERM;
> +
> +	return res.a0;
> +}
> +

Similar to rsi_attestation_token_init(), the return value type needs to be 'long'
since '-EPERM' can be returned from the function.

> +/**
> + * rsi_attestation_token_init - Initialise the operation to retrieve an
> + * attestation token.
> + *
> + * @challenge:	The challenge data to be used in the attestation token
> + *		generation.
> + * @size:	Size of the challenge data in bytes.
> + *
> + * Initialises the attestation token generation and returns an upper bound
> + * on the attestation token size that can be used to allocate an adequate
> + * buffer. The caller is expected to subsequently call
> + * rsi_attestation_token_continue() to retrieve the attestation token data on
> + * the same CPU.
> + *
> + * Returns:
> + *  On success, returns the upper limit of the attestation report size.
> + *  Otherwise, -EINVAL
> + */
> +static inline long
> +rsi_attestation_token_init(const u8 *challenge, unsigned long size)
> +{
> +	struct arm_smccc_1_2_regs regs = { 0 };
> +
> +	/* The challenge must be at least 32bytes and at most 64bytes */
> +	if (!challenge || size < 32 || size > 64)
> +		return -EINVAL;
> +
> +	regs.a0 = SMC_RSI_ATTESTATION_TOKEN_INIT;
> +	memcpy(&regs.a1, challenge, size);
> +	arm_smccc_1_2_smc(&regs, &regs);
> +
> +	if (regs.a0 == RSI_SUCCESS)
> +		return regs.a1;
> +
> +	return -EINVAL;
> +}
> +
> +/**
> + * rsi_attestation_token_continue - Continue the operation to retrieve an
> + * attestation token.
> + *
> + * @granule: {I}PA of the Granule to which the token will be written.
> + * @offset:  Offset within Granule to start of buffer in bytes.
> + * @size:    The size of the buffer.
> + * @len:     The number of bytes written to the buffer.
> + *
> + * Retrieves up to a RSI_GRANULE_SIZE worth of token data per call. The caller
> + * is expected to call rsi_attestation_token_init() before calling this
> + * function to retrieve the attestation token.
> + *
> + * Return:
> + * * %RSI_SUCCESS     - Attestation token retrieved successfully.
> + * * %RSI_INCOMPLETE  - Token generation is not complete.
> + * * %RSI_ERROR_INPUT - A parameter was not valid.
> + * * %RSI_ERROR_STATE - Attestation not in progress.
> + */
> +static inline int rsi_attestation_token_continue(phys_addr_t granule,
> +						 unsigned long offset,
> +						 unsigned long size,
> +						 unsigned long *len)
> +{
> +	struct arm_smccc_res res;
> +
> +	arm_smccc_1_1_invoke(SMC_RSI_ATTESTATION_TOKEN_CONTINUE,
> +			     granule, offset, size, 0, &res);
> +
> +	if (len)
> +		*len = res.a1;
> +	return res.a0;
> +}
> +

The return value type of this function needs to be 'unsigned long' even it's
converted to 'int' in arm_cca_attestation_continue(). In this way, the wrapper
functions has consistent return value type, which is 'unsigned long' or 'long'.

Thanks,
Gavin