Re: [XEN PATCH v8 11/22] xen/arm: ffa: send guest events to Secure Partitions

[Julien Grall <julien@xxxxxxx>]

Hi,

On 13/04/2023 08:14, Jens Wiklander wrote:
> +static int32_t ffa_direct_req_send_vm(uint16_t sp_id, uint16_t vm_id,
> +                                      uint8_t msg)
> +{
> +    uint32_t exp_resp = FFA_MSG_FLAG_FRAMEWORK;
> +    int32_t res;
> +
> +    if ( msg == FFA_MSG_SEND_VM_CREATED )
> +        exp_resp |= FFA_MSG_RESP_VM_CREATED;
> +    else if ( msg == FFA_MSG_SEND_VM_DESTROYED )
> +        exp_resp |= FFA_MSG_RESP_VM_DESTROYED;
> +    else
> +        return FFA_RET_INVALID_PARAMETERS;
> +
> +    do {
> +        const struct arm_smccc_1_2_regs arg = {
> +            .a0 = FFA_MSG_SEND_DIRECT_REQ_32,
> +            .a1 = sp_id,
> +            .a2 = FFA_MSG_FLAG_FRAMEWORK | msg,
> +            .a5 = vm_id,
> +        };
> +        struct arm_smccc_1_2_regs resp;
> +
> +        arm_smccc_1_2_smc(&arg, &resp);
> +        if ( resp.a0 != FFA_MSG_SEND_DIRECT_RESP_32 || resp.a2 != exp_resp )
> +        {
> +            /*
> +             * This is an invalid response, likely due to some error in the
> +             * implementation of the ABI.
> +             */
> +            return FFA_RET_INVALID_PARAMETERS;
> +        }
> +        res = resp.a3;
> +    } while ( res == FFA_RET_INTERRUPTED || res == FFA_RET_RETRY );
This loop seems potentially unbounded to me. Can you add a comment 
explaining why this is fine?
> +
> +    return res;
> +}
> +
Cheers,

--
Julien Grall