From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34299) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1c6tDD-0007Ne-1M for qemu-devel@nongnu.org; Wed, 16 Nov 2016 00:56:48 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1c6tD9-0006Pc-2M for qemu-devel@nongnu.org; Wed, 16 Nov 2016 00:56:47 -0500 Received: from mga07.intel.com ([134.134.136.100]:54977) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1c6tD8-0006PN-P2 for qemu-devel@nongnu.org; Wed, 16 Nov 2016 00:56:42 -0500 Message-ID: <582BF432.6030506@intel.com> Date: Wed, 16 Nov 2016 13:52:50 +0800 From: Jike Song MIME-Version: 1.0 References: <1479138156-28905-1-git-send-email-kwankhede@nvidia.com> <1479138156-28905-13-git-send-email-kwankhede@nvidia.com> <582AAF16.5080906@intel.com> <20161115081908.070b10ae@t450s.home> In-Reply-To: <20161115081908.070b10ae@t450s.home> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v12 12/22] vfio: Add notifier callback to parent's ops structure of mdev List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex Williamson Cc: Kirti Wankhede , pbonzini@redhat.com, kraxel@redhat.com, cjia@nvidia.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, kevin.tian@intel.com, bjsdjshi@linux.vnet.ibm.com, linux-kernel@vger.kernel.org On 11/15/2016 11:19 PM, Alex Williamson wrote: > On Tue, 15 Nov 2016 14:45:42 +0800 > Jike Song wrote: > >> On 11/14/2016 11:42 PM, Kirti Wankhede wrote: >>> Add a notifier calback to parent's ops structure of mdev device so that per >>> device notifer for vfio module is registered through vfio_mdev module. >>> >>> Signed-off-by: Kirti Wankhede >>> Signed-off-by: Neo Jia >>> Change-Id: Iafa6f1721aecdd6e50eb93b153b5621e6d29b637 >>> --- >>> drivers/vfio/mdev/vfio_mdev.c | 19 +++++++++++++++++++ >>> include/linux/mdev.h | 9 +++++++++ >>> 2 files changed, 28 insertions(+) >>> >>> diff --git a/drivers/vfio/mdev/vfio_mdev.c b/drivers/vfio/mdev/vfio_mdev.c >>> index ffc36758cb84..1694b1635607 100644 >>> --- a/drivers/vfio/mdev/vfio_mdev.c >>> +++ b/drivers/vfio/mdev/vfio_mdev.c >>> @@ -24,6 +24,15 @@ >>> #define DRIVER_AUTHOR "NVIDIA Corporation" >>> #define DRIVER_DESC "VFIO based driver for Mediated device" >>> >>> +static int vfio_mdev_notifier(struct notifier_block *nb, unsigned long action, >>> + void *data) >>> +{ >>> + struct mdev_device *mdev = container_of(nb, struct mdev_device, nb); >>> + struct parent_device *parent = mdev->parent; >>> + >>> + return parent->ops->notifier(mdev, action, data); >>> +} >>> + >>> static int vfio_mdev_open(void *device_data) >>> { >>> struct mdev_device *mdev = device_data; >>> @@ -40,6 +49,11 @@ static int vfio_mdev_open(void *device_data) >>> if (ret) >>> module_put(THIS_MODULE); >>> >>> + if (likely(parent->ops->notifier)) { >>> + mdev->nb.notifier_call = vfio_mdev_notifier; >>> + if (vfio_register_notifier(&mdev->dev, &mdev->nb)) >>> + pr_err("Failed to register notifier for mdev\n"); >>> + } >> >> Hi Kirti, >> >> Could you please move the notifier registration before parent->ops->open()? >> as you might know, I'm extending your vfio_register_notifier to also include >> the attaching/detaching events of vfio_group and kvm. Basically if vfio_group >> not attached to any kvm instance, the parent->ops->open() should return -ENODEV >> to indicate the failure, but to know whether kvm is available in open(), the >> notifier registration should be earlier. > > It seems like you're giving general guidance for how a vendor driver > open() function should work, yet a hard dependency on KVM should be > discouraged. You're making a choice for your vendor driver alone. I apologize for any confusion, but all I meant here was, if the real world requires a vendor driver to indicate errors instead of false success, it has to know some information before making the choice. > I would also be very cautious about the coherency of signaling the KVM > association relative to the user of the group. Is it possible that the > association of one KVM instance by a user of the group can leak to the > next user? Does vfio need to seen a gratuitous un-set of the KVM > association on group close()? etc. Thanks, I failed to see how this is possible, per my understanding the vfio_group_set_kvm gets called twice (once with kvm, another with NULL) during kvm's holding the group reference. Would you elaborate a bit more? -- Thanks, Jike