linux-kernel - Re: [PATCH v8 7/7] KVM: arm64: Support FFA_MSG_SEND_DIRECT

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Message-ID: <aIjuuTf2az25A7jW@willie-the-truck>
Date: Tue, 29 Jul 2025 16:54:33 +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 v8 7/7] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in
 host handler

On Sat, Jul 19, 2025 at 02:11:29AM +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 | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index f6d964df53c3e21ba85984f35cc7b6859012d1b0..363374408b354a5d65861b9cf140974d8914ff40 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -851,6 +851,15 @@ 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)
> +{
> +	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
> +
> +	arm_smccc_1_2_smc(args, regs);
> +}
> +
>  bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
>  {
>  	struct arm_smccc_1_2_regs res;
> @@ -909,11 +918,18 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
>  	case FFA_PARTITION_INFO_GET:
>  		do_ffa_part_get(&res, host_ctxt);
>  		goto out_handled;
> +	case FFA_MSG_SEND_DIRECT_REQ2:
> +		if (hyp_ffa_version >= FFA_VERSION_1_2) {
> +			do_ffa_direct_msg2(&res, host_ctxt, HOST_FFA_ID);
> +			goto out_handled;

I think it would be cleaner if ffa_call_supported() returned false for
this when the FFA version is < 1.2

Will