From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Krowiak Subject: Re: [PATCH v5 04/13] s390: vfio-ap: base implementation of VFIO AP device driver Date: Thu, 14 Jun 2018 09:04:12 -0400 Message-ID: <6ff0eac2-7c0f-4ab1-6301-c7f6997be591@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> <7237751c-66b5-d14c-5b71-cc1cfc79db87@linux.ibm.com> <20180613141221.5b924348.cohuck@redhat.com> <65ec9340-6a25-20ac-3078-f67992d5cc15@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <65ec9340-6a25-20ac-3078-f67992d5cc15@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: pmorel@linux.ibm.com, 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 06/13/2018 08:16 AM, Pierre Morel wrote: > On 13/06/2018 14:12, Cornelia Huck wrote: >> On Wed, 13 Jun 2018 14:01:54 +0200 >> Pierre Morel wrote: >> >>> 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 ? >> It does not need to know; the code registering the structure needs to >> set up device->release correctly. > > yes right, thanks. See the vfio_ap_matrix_dev_release() callback. > > >> >>>>>>>> + >>>>>>>> +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. >>> >