From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH net 4/5] net/smc: atomic SMCD cursor handling
Date: Tue, 13 Nov 2018 14:53:47 -0800 (PST)
Message-ID: <20181113.145347.202584017982412625.davem@davemloft.net>
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From: Ursula Braun <ubraun@linux.ibm.com>
Date: Mon, 12 Nov 2018 17:01:32 +0100

> +/* SMC-D cursor format */
> +union smcd_cdc_cursor {
 ...
> +} __aligned(8);

>  struct smcd_cdc_msg {
 ...
> +	union smcd_cdc_cursor	prod;
> +	union smcd_cdc_cursor	cons;
>  	u8 res3[8];
>  } __packed;

You're asking for 8-byte alignment of an object you only embed in a
__packed structure, which therefore has arbitary alignment.

It's not going to work.