linux-kernel - Re: [PATCH v7 5/5] KVM: arm64: Support FFA_MSG_SEND_DIRECT

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Message-ID: <aHpRvBO864x1vvqP@willie-the-truck>
Date: Fri, 18 Jul 2025 14:53:00 +0100
From: Will Deacon <will@...nel.org>
To: perlarsen@...gle.com
Cc: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
	Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, ahomescu@...gle.com,
	armellel@...gle.com, arve@...roid.com, ayrton@...gle.com,
	qperret@...gle.com, sebastianene@...gle.com, qwandor@...gle.com
Subject: Re: [PATCH v7 5/5] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in
 host handler

On Tue, Jul 01, 2025 at 10:06:38PM +0000, Per Larsen via B4 Relay wrote:
> From: Per Larsen <perlarsen@...gle.com>
> 
> FF-A 1.2 adds the DIRECT_REQ2 messaging interface which is similar to
> the existing FFA_MSG_SEND_DIRECT_{REQ,RESP} functions except that it
> uses the SMC calling convention v1.2 which allows calls to use x4-x17 as
> argument and return registers. Add support for FFA_MSG_SEND_DIRECT_REQ2
> in the host ffa handler.
> 
> Signed-off-by: Per Larsen <perlarsen@...gle.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 24 +++++++++++++++++++++++-
>  include/linux/arm_ffa.h       |  2 ++
>  2 files changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 79d834120a3f3d26e17e9170c60012b60c6f5a5e..21225988a9365219ccfd69e8e599d7403b5cdf05 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -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 */

I think that's the only change needed. In fact, maybe just don't add it
in the earlier patch?

>  	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 */
> @@ -862,6 +861,22 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
>  	hyp_spin_unlock(&host_buffers.lock);
>  }
>  
> +static void do_ffa_direct_msg2(struct arm_smccc_1_2_regs *regs,
> +			       struct kvm_cpu_context *ctxt,
> +			       u64 vm_handle)
> +{
> +	DECLARE_REG(u32, endp, ctxt, 1);
> +
> +	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
> +
> +	if (FIELD_GET(FFA_SRC_ENDPOINT_MASK, endp) != vm_handle) {
> +		ffa_to_smccc_error(regs, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}

Why do we care about checking the src id? We don't check that for
FFA_MSG_SEND_DIRECT_REQ and I don't think we need to care about it here
either.

Will