Re: [PATCH v6 14/15] s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The 'migratable' feature is unconditionally advertised in sysfs, even when migration is unsupported and explicitly disabled.
--

--- Patch [14]: [PATCH v6 14/15] s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute ---
commit 4ed92108ce1d93cfce3f8740cc391bfad091179c
Author: Anthony Krowiak <akrowiak@linux.ibm.com>

s390/vfio-ap: Add 'migratable' feature to sysfs 'features' attribute

This commit adds the 'migratable' feature to the sysfs features attribute 
to indicate that migration of vfio devices is supported.

> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index 8e69ed286bb9c..4e973736522bc 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -26,9 +26,11 @@ MODULE_LICENSE("GPL v2");
>  struct ap_matrix_dev *matrix_dev;
>  debug_info_t *vfio_ap_dbf_info;
>  
> +#define FEATURES "guest_matrix hotplug ap_config migratable"
> +
>  static ssize_t features_show(struct device *dev, struct device_attribute *attr, char *buf)
>  {
> -	return sysfs_emit(buf, "guest_matrix hotplug ap_config\n");
> +	return sysfs_emit(buf, "%s\n", FEATURES);

[Severity: Medium]
Will this unconditionally advertise the migratable feature even when the
environment does not support it?

If the system is running as a Secure Execution (SE) guest, migration is
typically disabled. By hardcoding "migratable" into the FEATURES string,
management tools like libvirt querying the features sysfs attribute might
incorrectly assume migration is supported. 

This could lead orchestrators to make incorrect VM placement decisions,
followed by unexpected migration failures when QEMU rejects the migration
because the VFIO mdev lacks the capability.

Should features_show() check environmental constraints, such as
ap_is_se_guest(), before including the migratable flag in the output?

>  }
>  static DEVICE_ATTR_RO(features);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260727173239.2420754-1-akrowiak@linux.ibm.com?part=14