linux-kernel - Re: [PATCH 2/2] KVM: arm64: support optional calls of FF-A v1.2

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Message-ID: <f5aa3c19-fdea-4f62-9541-530e59b20a87@arm.com>
Date: Tue, 28 Oct 2025 10:26:05 +0000
From: Ben Horgan <ben.horgan@....com>
To: Yeoreum Yun <yeoreum.yun@....com>, maz@...nel.org,
 oliver.upton@...ux.dev, joey.gouly@....com, suzuki.poulose@....com,
 yuzenghui@...wei.com, catalin.marinas@....com, will@...nel.org,
 perlarsen@...gle.com, ayrton@...gle.com
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] KVM: arm64: support optional calls of FF-A v1.2

Hi Levi,

On 10/27/25 19:17, Yeoreum Yun wrote:
> To use TPM drvier which uses CRB over FF-A with FFA_DIRECT_REQ2,
> support the FF-A v1.2's optinal calls by querying whether
> SPMC supports those.
> 
> Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 19 ++++++++++++++++++-
>  1 file changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 0ae87ff61758..9ded1c6369b9 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -646,6 +646,22 @@ static void do_ffa_mem_reclaim(struct arm_smccc_1_2_regs *res,
>  		ffa_to_smccc_res(res, ret);
>  }
>  
> +static bool ffa_1_2_optional_calls_supported(u64 func_id)
> +{
> +	struct arm_smccc_1_2_regs res;
> +
> +	if (!smp_load_acquire(&has_version_negotiated) ||
> +		(FFA_MINOR_VERSION(FFA_VERSION_1_2) < 2))
> +		return false;
> +
> +	arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> +		.a0 = FFA_FEATURES,
> +		.a1 = func_id,
> +	}, &res);
> +
> +	return res.a0 == FFA_SUCCESS;
> +}
> +
>  /*
>   * Is a given FFA function supported, either by forwarding on directly
>   * or by handling at EL2?
> @@ -678,12 +694,13 @@ static bool ffa_call_supported(u64 func_id)
>  	case FFA_NOTIFICATION_SET:
>  	case FFA_NOTIFICATION_GET:
>  	case FFA_NOTIFICATION_INFO_GET:
> +		return false;
>  	/* Optional interfaces added in FF-A 1.2 */
>  	case FFA_MSG_SEND_DIRECT_REQ2:		/* Optional per 7.5.1 */
>  	case FFA_MSG_SEND_DIRECT_RESP2:		/* Optional per 7.5.1 */
>  	case FFA_CONSOLE_LOG:			/* Optional per 13.1: not in Table 13.1 */

Looking at table 13.54 in the FF-A 1.2 spec FFA_CONSOLE_LOG is only supported in secure FF-A
instances and not from the normal world.

>  	case FFA_PARTITION_INFO_GET_REGS:	/* Optional for virtual instances per 13.1 */
> -		return false;
> +		return ffa_1_2_optional_calls_supported(func_id);
>  	}

I don't think that an smc call here is the right thing to do. This changes this from a light 
weight deny list to an extra smc call for each ffa_msg_send_direct_req2 from the driver.

Instead, I would expect this patch just to remove FFA_MSG_SEND_DIRECT_REQ2 from the deny list
and rely on the TPM driver to use FFA_FEATURES to check whether it's supported.

So, just this change:

@@ -679,7 +679,6 @@ static bool ffa_call_supported(u64 func_id)
        case FFA_NOTIFICATION_GET:
        case FFA_NOTIFICATION_INFO_GET:
        /* Optional interfaces added in FF-A 1.2 */
-       case FFA_MSG_SEND_DIRECT_REQ2:          /* Optional per 7.5.1 */
        case FFA_MSG_SEND_DIRECT_RESP2:         /* Optional per 7.5.1 */
        case FFA_CONSOLE_LOG:                   /* Optional per 13.1: not in Table 13.1 */
        case FFA_PARTITION_INFO_GET_REGS:       /* Optional for virtual instances per 13.1 */

Am I missing something?

>  
>  	return true; 
Thanks,

Ben