Re: [PATCH v7 2/3] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host handler

[Vincent Donnefort <vdonnefort@google.com>]

On Sun, Aug 30, 2026 at 11:08:14PM +0000, Per Larsen via B4 Relay wrote:
> From: Sebastian Ene <sebastianene@google.com>
> 
> Allow direct messages to be forwarded from the host. The host should
> not be sending framework messages so they are filtered out.
> 
> Signed-off-by: Sebastian Ene <sebastianene@google.com>
> Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
> Signed-off-by: Per Larsen <perlarsen@google.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/ffa.c | 27 +++++++++++++++++++++++++++
>  include/linux/arm_ffa.h       |  2 ++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 9e8bb95e8845..96cf6be969de 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -880,6 +880,29 @@ 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)
> +{
> +	DECLARE_REG(u64, endp, ctxt, 1);
> +	DECLARE_REG(u64, flags, ctxt, 2);
> +
> +	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];


For a next version, ffa_check_unused_args_sbz() has just been merged. [1]

[1] https://lore.kernel.org/all/20260907171930.4037166-8-sebastianene@google.com/

-- 
Vincent

> +
> +	if (upper_32_bits(endp) ||
> +	    FIELD_GET(FFA_SRC_ENDPOINT_MASK, endp) != HOST_FFA_ID) {
> +		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}
> +
> +	/* filter out framework messages and validate SBZ/MBZ bits */
> +	if (flags) {
> +		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
> +		return;
> +	}
> +
> +	hyp_smccc_1_2_smc(args, res);
> +}
> +
>  bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
>  {
>  	struct arm_smccc_1_2_regs res = {0};
> @@ -938,6 +961,10 @@ 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_REQ:
> +	case FFA_FN64_MSG_SEND_DIRECT_REQ:
> +		do_ffa_direct_msg(&res, host_ctxt);
> +		goto out_handled;
>  	}
>  
>  	if (ffa_call_supported(func_id))
> diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
> index e71d83ee0aef..a3f44e7c08de 100644
> --- a/include/linux/arm_ffa.h
> +++ b/include/linux/arm_ffa.h
> @@ -269,6 +269,8 @@ bool ffa_partition_check_property(struct ffa_device *dev, u32 property)
>  	(ffa_partition_check_property(dev, FFA_PARTITION_DIRECT_REQ2_RECV) && \
>  	 !dev->mode_32bit)
>  
> +#define FFA_SRC_ENDPOINT_MASK	GENMASK(31, 16)
> +
>  /* For use with FFA_MSG_SEND_DIRECT_{REQ,RESP} which pass data via registers */
>  struct ffa_send_direct_data {
>  	unsigned long data0; /* w3/x3 */
> 
> -- 
> 2.55.0.897.gb25b4bd76c-goog
> 
> 
>