From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre Morel Subject: Re: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP device driver Date: Wed, 13 Jun 2018 14:01:54 +0200 Message-ID: <7237751c-66b5-d14c-5b71-cc1cfc79db87@linux.ibm.com> References: <1525705912-12815-1-git-send-email-akrowiak@linux.vnet.ibm.com> <1525705912-12815-5-git-send-email-akrowiak@linux.vnet.ibm.com> <889b8d41-e08c-0eb5-2de0-a1d6669a03b3@linux.ibm.com> <20180613094812.1fd1846d.cohuck@redhat.com> <41e7ccbd-f6f5-ba20-f236-7824c682994d@linux.ibm.com> <20180613131402.0305d092.cohuck@redhat.com> Reply-To: pmorel@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20180613131402.0305d092.cohuck@redhat.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Cornelia Huck Cc: Tony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, freude@de.ibm.com, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, borntraeger@de.ibm.com, kwankhede@nvidia.com, bjsdjshi@linux.vnet.ibm.com, pbonzini@redhat.com, alex.williamson@redhat.com, pmorel@linux.vnet.ibm.com, alifm@linux.vnet.ibm.com, mjrosato@linux.vnet.ibm.com, jjherne@linux.vnet.ibm.com, thuth@redhat.com, pasic@linux.vnet.ibm.com, berrange@redhat.com, fiuczy@linux.vnet.ibm.com, buendgen@de.ibm.com List-ID: On 13/06/2018 13:14, Cornelia Huck wrote: > On Wed, 13 Jun 2018 12:54:40 +0200 > Pierre Morel wrote: > >> On 13/06/2018 09:48, Cornelia Huck wrote: >>> On Wed, 13 Jun 2018 09:41:16 +0200 >>> Pierre Morel 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? > No, the put callback for the embedding structure needs to take care of > freeing things. Otherwise it is buggy. Seems buggy to me. How does the put_device knows if it is embedded and then in what it is embedded ? > >>> >>>> >>>>> + >>>>> +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