linux-kernel - Re: [PATCH v3 2/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT

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Message-ID: <aV_Ngc2KKKZYLH1m@willie-the-truck>
Date: Thu, 8 Jan 2026 15:30:09 +0000
From: Will Deacon <will@...nel.org>
To: perlarsen@...gle.com
Cc: Marc Zyngier <maz@...nel.org>, Joey Gouly <joey.gouly@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Zenghui Yu <yuzenghui@...wei.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Yeoreum Yun <yeoreum.yun@....com>, Ben Horgan <ben.horgan@....com>,
	Oliver Upton <oupton@...nel.org>,
	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 v3 2/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ2 in
 host handler

On Wed, Nov 19, 2025 at 02:07:54AM +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 and can use the
> existing handler function. Add support for FFA_MSG_SEND_DIRECT_REQ2 in
> the host ffa handler.
> 
> Reviewed-by: Yeoreum Yun <yeoreum.yun@....com>
> Signed-off-by: Per Larsen <perlarsen@...gle.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index a38a3ab497e5eac11777109684a33f02d88d09a1..c794802bda589b315faf978086ad164a2aee510a 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -683,8 +683,10 @@ 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 */
> +		return hyp_ffa_version >= FFA_VERSION_1_2;

You might as well just move this to the end and avoid having to add the
'return false' above.

>  	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 */
> @@ -866,12 +868,16 @@ static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
>  			      struct kvm_cpu_context *ctxt,
>  			      u64 vm_handle)
>  {
> +	DECLARE_REG(u64, func_id, ctxt, 0);
>  	DECLARE_REG(u32, flags, ctxt, 2);
>  
>  	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
>  
> -	/* filter out framework messages */
> -	if (FIELD_GET(FFA_MSG_FLAGS_MSG_TYPE, flags)) {
> +	/*
> +	 * filter out framework messages.
> +	 * FFA_MSG_SEND_DIRECT_REQ2 is only for partition messages.
> +	 */
> +	if (func_id != FFA_MSG_SEND_DIRECT_REQ2 && FIELD_GET(FFA_MSG_FLAGS_MSG_TYPE, flags)) {
>  		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
>  		return;
>  	}

It would probably be better to switch the polarity of this check so that
you look at flags if FFA_MSG_SEND_DIRECT_REQ or
FFA_FN64_MSG_SEND_DIRECT_REQ rather than if !REQ2.

and again, I'm not seeing what the 'vm_handle' argument is doing here.

Will