From: Jason Wang <jasowang@redhat.com> To: Jason Gunthorpe <jgg@mellanox.com> Cc: "mst@redhat.com" <mst@redhat.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "virtualization@lists.linux-foundation.org" <virtualization@lists.linux-foundation.org>, "netdev@vger.kernel.org" <netdev@vger.kernel.org>, "tiwei.bie@intel.com" <tiwei.bie@intel.com>, "maxime.coquelin@redhat.com" <maxime.coquelin@redhat.com>, "cunming.liang@intel.com" <cunming.liang@intel.com>, "zhihong.wang@intel.com" <zhihong.wang@intel.com>, "rob.miller@broadcom.com" <rob.miller@broadcom.com>, "xiao.w.wang@intel.com" <xiao.w.wang@intel.com>, "haotian.wang@sifive.com" <haotian.wang@sifive.com>, "lingshan.zhu@intel.com" <lingshan.zhu@intel.com>, "eperezma@redhat.com" <eperezma@redhat.com>, "lulu@redhat.com" <lulu@redhat.com>, Parav Pandit <parav@mellanox.com>, "kevin.tian@intel.com" <kevin.tian@intel.com>, "stefanha@redhat.com" <stefanha@redhat.com>, "rdunlap@infradead.org" <rdunlap@infradead.org>, "hch@infradead.org" <hch@infradead.org>, "aadam@redhat.com" <aadam@redhat.com>, "jakub.kicinski@netronome.com" <jakub.kicinski@netronome.com>, Jiri Pirko <jiri@mellanox.com>, Shahaf Shuler <shahafs@mellanox.com>, "hanand@xilinx.com" <hanand@xilinx.com>, "mhabets@solarflare.com" <mhabets@solarflare.com> Subject: Re: [PATCH 4/5] virtio: introduce a vDPA based transport Date: Mon, 20 Jan 2020 15:52:12 +0800 Message-ID: <bff37791-9640-39e0-5e93-c905ebfb5d2b@redhat.com> (raw) In-Reply-To: <20200117140013.GV20978@mellanox.com> On 2020/1/17 下午10:00, Jason Gunthorpe wrote: > On Fri, Jan 17, 2020 at 05:32:35PM +0800, Jason Wang wrote: >>>> + const struct vdpa_config_ops *ops = vdpa->config; >>>> + struct virtio_vdpa_device *vd_dev; >>>> + int rc; >>>> + >>>> + vd_dev = devm_kzalloc(dev, sizeof(*vd_dev), GFP_KERNEL); >>>> + if (!vd_dev) >>>> + return -ENOMEM; >>> This is not right, the struct device lifetime is controled by a kref, >>> not via devm. If you want to use a devm unwind then the unwind is >>> put_device, not devm_kfree. >> I'm not sure I get the point here. The lifetime is bound to underlying vDPA >> device and devres allow to be freed before the vpda device is released. But >> I agree using devres of underlying vdpa device looks wired. > Once device_initialize is called the only way to free a struct device > is via put_device, while here you have a devm trigger that will > unconditionally do kfree on a struct device without respecting the > reference count. > > reference counted memory must never be allocated with devm. Right, fixed. > >>>> + vd_dev->vdev.dev.release = virtio_vdpa_release_dev; >>>> + vd_dev->vdev.config = &virtio_vdpa_config_ops; >>>> + vd_dev->vdpa = vdpa; >>>> + INIT_LIST_HEAD(&vd_dev->virtqueues); >>>> + spin_lock_init(&vd_dev->lock); >>>> + >>>> + vd_dev->vdev.id.device = ops->get_device_id(vdpa); >>>> + if (vd_dev->vdev.id.device == 0) >>>> + return -ENODEV; >>>> + >>>> + vd_dev->vdev.id.vendor = ops->get_vendor_id(vdpa); >>>> + rc = register_virtio_device(&vd_dev->vdev); >>>> + if (rc) >>>> + put_device(dev); >>> And a ugly unwind like this is why you want to have device_initialize() >>> exposed to the driver, >> In this context, which "driver" did you mean here? (Note, virtio-vdpa is the >> driver for vDPA bus here). > 'driver' is the thing using the 'core' library calls to implement a > device, so here the 'vd_dev' is the driver and > 'register_virtio_device' is the core Ok. > >>> Where is the various THIS_MODULE's I expect to see in a scheme like >>> this? >>> >>> All function pointers must be protected by a held module reference >>> count, ie the above probe/remove and all the pointers in ops. >> Will double check, since I don't see this in other virtio transport drivers >> (PCI or MMIO). > pci_register_driver is a macro that provides a THIS_MODULE, and the > pci core code sets driver.owner, then the rest of the stuff related to > driver ops is supposed to work against that to protect the driver ops. > > For the device module refcounting you either need to ensure that > 'unregister' is a strong fence and guanentees that no device ops are > called past unregister (noting that this is impossible for release), > or you need to hold the module lock until release. > > It is common to see non-core subsystems get this stuff wrong. > > Jason Ok. I see. Thanks
next prev parent reply index Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-01-16 12:42 [PATCH 0/5] vDPA support Jason Wang 2020-01-16 12:42 ` [PATCH 1/5] vhost: factor out IOTLB Jason Wang 2020-01-17 4:14 ` Randy Dunlap 2020-01-17 9:34 ` Jason Wang 2020-01-18 0:01 ` kbuild test robot 2020-01-18 0:40 ` kbuild test robot 2020-01-16 12:42 ` [PATCH 2/5] vringh: IOTLB support Jason Wang 2020-01-17 21:54 ` kbuild test robot 2020-01-17 22:33 ` kbuild test robot 2020-01-16 12:42 ` [PATCH 3/5] vDPA: introduce vDPA bus Jason Wang 2020-01-16 15:22 ` Jason Gunthorpe 2020-01-17 3:03 ` Jason Wang 2020-01-17 13:54 ` Jason Gunthorpe 2020-01-20 7:50 ` Jason Wang 2020-01-20 12:17 ` Michael S. Tsirkin 2020-01-20 17:50 ` Jason Gunthorpe 2020-01-20 21:56 ` Michael S. Tsirkin 2020-01-21 14:12 ` Jason Gunthorpe 2020-01-21 14:15 ` Michael S. Tsirkin 2020-01-21 14:16 ` Jason Gunthorpe 2020-01-21 8:40 ` Tian, Kevin 2020-01-21 9:41 ` Jason Wang 2020-01-17 4:16 ` Randy Dunlap 2020-01-17 9:34 ` Jason Wang 2020-01-17 12:13 ` Michael S. Tsirkin 2020-01-17 13:52 ` Jason Wang [not found] ` <CAJPjb1+fG9L3=iKbV4Vn13VwaeDZZdcfBPvarogF_Nzhk+FnKg@mail.gmail.com> 2020-01-19 9:07 ` Shahaf Shuler 2020-01-19 9:59 ` Michael S. Tsirkin 2020-01-20 8:44 ` Jason Wang 2020-01-20 12:09 ` Michael S. Tsirkin 2020-01-21 3:32 ` Jason Wang 2020-01-20 8:43 ` Jason Wang 2020-01-20 17:49 ` Jason Gunthorpe 2020-01-20 20:51 ` Shahaf Shuler 2020-01-20 21:25 ` Michael S. Tsirkin 2020-01-20 21:47 ` Shahaf Shuler 2020-01-20 21:59 ` Michael S. Tsirkin 2020-01-21 6:01 ` Shahaf Shuler 2020-01-21 7:57 ` Jason Wang 2020-01-21 14:07 ` Jason Gunthorpe 2020-01-21 14:16 ` Michael S. Tsirkin 2020-01-20 21:48 ` Michael S. Tsirkin 2020-01-21 4:00 ` Jason Wang 2020-01-21 5:47 ` Michael S. Tsirkin 2020-01-21 8:00 ` Jason Wang 2020-01-21 8:15 ` Michael S. Tsirkin 2020-01-21 8:35 ` Jason Wang 2020-01-21 11:09 ` Shahaf Shuler 2020-01-22 6:36 ` Jason Wang 2020-01-21 14:05 ` Jason Gunthorpe 2020-01-21 14:17 ` Michael S. Tsirkin 2020-01-22 6:18 ` Jason Wang 2020-01-20 8:19 ` Jason Wang 2020-01-16 12:42 ` [PATCH 4/5] virtio: introduce a vDPA based transport Jason Wang 2020-01-16 15:38 ` Jason Gunthorpe 2020-01-17 9:32 ` Jason Wang 2020-01-17 14:00 ` Jason Gunthorpe 2020-01-20 7:52 ` Jason Wang [this message] 2020-01-17 4:10 ` Randy Dunlap 2020-01-16 12:42 ` [PATCH 5/5] vdpasim: vDPA device simulator Jason Wang 2020-01-16 15:47 ` Jason Gunthorpe 2020-01-17 9:32 ` Jason Wang 2020-01-17 14:10 ` Jason Gunthorpe 2020-01-20 8:01 ` Jason Wang 2020-02-04 4:19 ` Jason Wang 2020-01-17 4:12 ` Randy Dunlap 2020-01-17 9:35 ` Jason Wang 2020-01-18 18:18 ` kbuild test robot 2020-01-28 3:32 ` Dan Carpenter 2020-02-04 4:07 ` Jason Wang 2020-02-04 8:21 ` Zhu Lingshan 2020-02-04 8:28 ` Jason Wang 2020-02-04 12:52 ` Jason Gunthorpe 2020-02-05 3:14 ` Jason Wang 2020-01-21 8:44 ` [PATCH 0/5] vDPA support Tian, Kevin 2020-01-21 9:39 ` Jason Wang
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