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Date:   Fri, 9 Apr 2021 15:35:36 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Haiyang Zhang <haiyangz@microsoft.com>
Cc:     David Miller <davem@davemloft.net>,
        Dexuan Cui <decui@microsoft.com>,
        "kuba@kernel.org" <kuba@kernel.org>,
        KY Srinivasan <kys@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        "wei.liu@kernel.org" <wei.liu@kernel.org>,
        Wei Liu <liuwe@microsoft.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "leon@kernel.org" <leon@kernel.org>,
        "bernd@petrovitsch.priv.at" <bernd@petrovitsch.priv.at>,
        "rdunlap@infradead.org" <rdunlap@infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Subject: Re: [PATCH v3 net-next] net: mana: Add a driver for Microsoft Azure
 Network Adapter (MANA)
Message-ID: <YHBYKGwJsX/wuYqn@lunn.ch>
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 For the structs containing variables with the same sizes, or already size aligned 
> variables, we knew the __packed has no effect. And for these structs, it doesn't 
> cause performance impact either, correct? 
> 
> But in the future, if different sized variables are added, the __packed may 
> become necessary again. To prevent anyone accidently forget to add __packed 
> when adding new variables to these structs, can we keep the __packed for all 
> messages going through the "wire"?

It should not be a problem because anybody adding new variables should
know packed is not liked in the kernel and will take care.

If you want to be paranoid add a BUILD_BUG_ON(size(struct foo) != 42);

   Andrew