linux-kernel - Re: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP device driver

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Date:   Wed, 13 Jun 2018 12:54:40 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Cornelia Huck <cohuck@...hat.com>
Cc:     Tony Krowiak <akrowiak@...ux.vnet.ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, freude@...ibm.com, schwidefsky@...ibm.com,
        heiko.carstens@...ibm.com, borntraeger@...ibm.com,
        kwankhede@...dia.com, bjsdjshi@...ux.vnet.ibm.com,
        pbonzini@...hat.com, alex.williamson@...hat.com,
        pmorel@...ux.vnet.ibm.com, alifm@...ux.vnet.ibm.com,
        mjrosato@...ux.vnet.ibm.com, jjherne@...ux.vnet.ibm.com,
        thuth@...hat.com, pasic@...ux.vnet.ibm.com, berrange@...hat.com,
        fiuczy@...ux.vnet.ibm.com, buendgen@...ibm.com
Subject: Re: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP
 device driver

On 13/06/2018 09:48, Cornelia Huck wrote:
> On Wed, 13 Jun 2018 09:41:16 +0200
> Pierre Morel <pmorel@...ux.ibm.com> wrote:
>
>> On 07/05/2018 17:11, Tony Krowiak wrote:
>>> Introduces a new AP device driver. This device driver
>>> is built on the VFIO mediated device framework. The framework
>>> provides sysfs interfaces that facilitate passthrough
>>> access by guests to devices installed on the linux host.
>> ...snip...
>>
>>> +static int vfio_ap_matrix_dev_create(void)
>>> +{
>>> +	int ret;
>>> +
>>> +	vfio_ap_root_device = root_device_register(VFIO_AP_ROOT_NAME);
>>> +
>>> +	if (IS_ERR(vfio_ap_root_device)) {
>>> +		ret = PTR_ERR(vfio_ap_root_device);
>>> +		goto done;
>>> +	}
>>> +
>>> +	ap_matrix = kzalloc(sizeof(*ap_matrix), GFP_KERNEL);
>>> +	if (!ap_matrix) {
>>> +		ret = -ENOMEM;
>>> +		goto matrix_alloc_err;
>>> +	}
>>> +
>>> +	ap_matrix->device.type = &vfio_ap_dev_type;
>>> +	dev_set_name(&ap_matrix->device, "%s", VFIO_AP_DEV_NAME);
>>> +	ap_matrix->device.parent = vfio_ap_root_device;
>>> +	ap_matrix->device.release = vfio_ap_matrix_dev_release;
>>> +	ap_matrix->device.driver = &vfio_ap_drv.driver;
>>> +
>>> +	ret = device_register(&ap_matrix->device);
>>> +	if (ret)
>>> +		goto matrix_reg_err;
>>> +
>>> +	goto done;
>>> +
>>> +matrix_reg_err:
>>> +	put_device(&ap_matrix->device);
>> Did not see this before but here you certainly want to
>> do a kfree and not a put_device.
> No, this must not be a kfree. Once you've tried to register something
> embedding a struct device with the driver core, you need to use
> put_device, as another path may have acquired a reference, even if
> registering ultimately failed. See the comment for device_register().
> IOW, the code is correct.

learned something again :) ,
but still, a kfree is needed for the kzalloc.
Does'nt it?

>
>>
>>
>>> +
>>> +matrix_alloc_err:
>>> +	root_device_unregister(vfio_ap_root_device);
>>> +
>>> +done:
>>> +	return ret;
>>> +}
>>> +
>>> +static void vfio_ap_matrix_dev_destroy(struct ap_matrix *ap_matrix)
>>> +{
>>> +	device_unregister(&ap_matrix->device);
>>> +	root_device_unregister(vfio_ap_root_device);
>> Also here you need a kfree(ap_matrix) too .
> Same here.
>

-- 
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany