linux-kernel - Re: [PATCH 1/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT

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Message-ID: <aQNsrjceYM3RvY0e@e129823.arm.com>
Date: Thu, 30 Oct 2025 13:48:30 +0000
From: Yeoreum Yun <yeoreum.yun@....com>
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>,
	Will Deacon <will@...nel.org>, Ben Horgan <ben.horgan@....com>,
	Armelle Laine <armellel@...gle.com>,
	Sebastien Ene <sebastianene@...gle.com>,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host
 handler

Hi Per and Sebasian,

>
> Allow direct messages to be forwarded from the host.
>
> Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
> 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 4e16f9b96f637599873b16148c6e40cf1210aa3e..191dcb301cca3986758fb6a49f15f1799de9f1d1 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -857,6 +857,15 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
>  	hyp_spin_unlock(&host_buffers.lock);
>  }
>
> +static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
> +			      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, res);
> +}
> +

TBH, I don't have a strong comment for this but, I'm not sure why
it is necessary.
Since it calls just "smc" with the passed argments,
I think it can be handled by default_smc_handler() without adding this
function but return the ture for DIRECT MSG2 in ffa_call_support().

Am I missing something?

>  bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
>  {
>  	struct arm_smccc_1_2_regs res;
> @@ -915,6 +924,13 @@ 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_ID_GET:
> +		ffa_to_smccc_res_prop(&res, FFA_RET_SUCCESS, HOST_FFA_ID);
> +		goto out_handled;

I think FFA_ID_GET should be a seperated patch?

> +	case FFA_MSG_SEND_DIRECT_REQ:
> +	case FFA_FN64_MSG_SEND_DIRECT_REQ:
> +		do_ffa_direct_msg(&res, host_ctxt, HOST_FFA_ID);
> +		goto out_handled;
>  	}
>
>  	if (ffa_call_supported(func_id))

Thanks.

--
Sincerely,
Yeoreum Yun