linux-kernel - Re: [PATCH v4 4/5] s390/vfio-ap: Add write support to sysfs attr ap

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Date: Mon, 8 Apr 2024 16:22:32 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: "Jason J. Herne" <jjherne@...ux.ibm.com>
Cc: linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        pasic@...ux.ibm.com, akrowiak@...ux.ibm.com, borntraeger@...ibm.com,
        gor@...ux.ibm.com, hca@...ux.ibm.com,
        Matthew Rosato <mjrosato@...ux.ibm.com>
Subject: Re: [PATCH v4 4/5] s390/vfio-ap: Add write support to sysfs attr
 ap_config

On Tue, Mar 26, 2024 at 12:47:05PM -0400, Jason J. Herne wrote:

Hi Jason,

This series still has some issues.

> +	newbuf = rest = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);

This line triggers a checkpatch warning. Would it make sense
to turn it into below instead?

	newbuf = kstrndup(buf, AP_CONFIG_STRLEN, GFP_KERNEL);
> +	if (!newbuf)
> +		return -ENOMEM;
	rest = newbuf;

Also, please address other checkpatch suggestions.

> +	/* Save old state */
> +	/* The volatile cast here is to work around a gcc false positive
> +	 * Wstringop-overread-warning.
> +	 */
> +	ap_matrix_copy(&m_old, (*(struct ap_matrix * volatile *)(&matrix_mdev->matrix)));

Could you please come up with a different workaround? This issue has already
been resolved in the past in different ways. See commit 34186b48d29b ("ARM:
sharpsl_param: work around -Wstringop-overread warning") for example.

Thanks!