From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44522 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753359AbeE3RPp (ORCPT ); Wed, 30 May 2018 13:15:45 -0400 Date: Wed, 30 May 2018 20:15:43 +0300 From: "Michael S. Tsirkin" To: "Duyck, Alexander H" Cc: "alexander.duyck@gmail.com" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "virtio-dev@lists.oasis-open.org" , "Rustad, Mark D" , "Daly, Dan" , "Bie, Tiwei" , "linux-pci@vger.kernel.org" , "bhelgaas@google.com" , "Liang, Cunming" , "Wang, Zhihong" Subject: Re: [virtio-dev] [PATCH] virtio_pci: support enabling VFs Message-ID: <20180530201034-mutt-send-email-mst@kernel.org> References: <20180530085521.26583-1-tiwei.bie@intel.com> <20180530192215-mutt-send-email-mst@kernel.org> <1527697588.16245.136.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1527697588.16245.136.camel@intel.com> Sender: linux-pci-owner@vger.kernel.org List-ID: On Wed, May 30, 2018 at 04:26:30PM +0000, Duyck, Alexander H wrote: > On Wed, 2018-05-30 at 19:22 +0300, Michael S. Tsirkin wrote: > > On Wed, May 30, 2018 at 09:10:57AM -0700, Alexander Duyck wrote: > > > On Wed, May 30, 2018 at 1:55 AM, Tiwei Bie wrote: > > > > There is a new feature bit allocated in virtio spec to > > > > support SR-IOV (Single Root I/O Virtualization): > > > > > > > > https://github.com/oasis-tcs/virtio-spec/issues/11 > > > > > > > > This patch enables the support for this feature bit in > > > > virtio driver. > > > > > > > > Signed-off-by: Tiwei Bie > > > > > > So from a quick glance it looks like we are leaving SR-IOV enabled if > > > the driver is removed. Do we want to have that behavior or should we > > > be adding the code to disable SR-IOV and free the VFs on driver > > > removal? > > > > Could pci core handle it for us somehow? > > Maybe, but it would require changes to the pci core to do it. > > The problem is some drivers want to leave the VFs there since the PF > doesn't really do anything, or they have the option of essentially > putting the VFs into a standby state when the PF is gone. > > My main concern is do we care if VFs are allocated and then somebody > removes the driver and binds a different driver to the interface? If > not then this code and be left as is, but I just wanted to be certain > since I know this isn't just enabling SR-IOV we are having to do a > number of other checks against the virtio device. Well the spec says features have to be negotiated, and since we reset the device when we unbind from it I think it's a given we should keep a driver bound to the PF. IOW until we are sure we need the capability to keep it enabled, let's disable it to be safe. -- MST