linux-kernel - RE: [PATCH] pvcalls-front: 64-bit align flags

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Message-ID: <139554adced44c5ea5aa4fab4f0ca8a0@AcuMS.aculab.com>
Date:   Wed, 28 Feb 2018 09:06:17 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Stefano Stabellini' <sstabellini@...nel.org>,
        "jgross@...e.com" <jgross@...e.com>,
        "boris.ostrovsky@...cle.com" <boris.ostrovsky@...cle.com>
CC:     "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] pvcalls-front: 64-bit align flags

From: Stefano Stabellini
> Sent: 27 February 2018 19:55
> 
> We are using test_and_* operations on the status and flag fields of
> struct sock_mapping. However, these functions require the operand to be
> 64-bit aligned on arm64. Currently, only status is 64-bit aligned.

That sounds like a big accident just waiting to happen...
If the operand is required to be 64bit aligned why isn't it a type
that requires 64bit alignment?

> Make flags 64-bit aligned by introducing an explicit padding field.

At some point such padding will always go wrong...

	David