RE: [PATCH 13/13] vfio/mdev: add mdev available instance checking to the core

From: "Tian, Kevin" <kevin.tian@intel.com>
To: Christoph Hellwig <hch@lst.de>,
	Kirti Wankhede <kwankhede@nvidia.com>,
	Tony Krowiak <akrowiak@linux.ibm.com>,
	Halil Pasic <pasic@linux.ibm.com>,
	Jason Herne <jjherne@linux.ibm.com>,
	Eric Farman <farman@linux.ibm.com>,
	Matthew Rosato <mjrosato@linux.ibm.com>,
	Zhenyu Wang <zhenyuw@linux.intel.com>,
	"Wang, Zhi A" <zhi.a.wang@intel.com>,
	"Alex Williamson" <alex.williamson@redhat.com>
Cc: "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
	"intel-gvt-dev@lists.freedesktop.org" 
	<intel-gvt-dev@lists.freedesktop.org>,
	Jason Gunthorpe <jgg@nvidia.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: RE: [PATCH 13/13] vfio/mdev: add mdev available instance checking to the core
Date: Tue, 14 Jun 2022 10:32:11 +0000	[thread overview]
Message-ID: <BN9PR11MB5276BB7AA39243BA5A21CFEC8CAA9@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20220614045428.278494-14-hch@lst.de>

> From: Christoph Hellwig
> Sent: Tuesday, June 14, 2022 12:54 PM
> 
> From: Jason Gunthorpe <jgg@nvidia.com>
> 
> Many of the mdev drivers use a simple counter for keeping track of the
> available instances. Move this code to the core code and store the counter
> in the mdev_type. Implement it using correct locking, fixing mdpy.
> 
> Drivers provide a the value in the mdev_driver at registration time and
> the core code provides a standard sysfs attribute to return the
> available_instances.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> [count instances per-parent instead of per-type]

per-parent counting works only if the parent doesn't have overlapping
instances between types. This is probably worth a clarification in doc.

> @@ -135,6 +136,7 @@ static void mdev_device_release(struct device *dev)
> 
>  	mutex_lock(&mdev_list_lock);
>  	list_del(&mdev->next);
> +	mdev->type->parent->available_instances++;

	if (!drv->get_available)
		mdev->type->parent->available_instances++;

Otherwise this looks good to me:

Reviewed-by: Kevin Tian <kevin.tian@intel.com>