> Subject: Re: [Patch v2] hv_netvsc: Mark VF as slave before exposing it to user- > mode > > On Fri, 27 Oct 2023 13:59:50 -0700 longli@xxxxxxxxxxxxxxxxx wrote: > > When a VF is being exposed form the kernel, it should be marked as "slave" > > before exposing to the user-mode. The VF is not usable without netvsc > > running as master. The user-mode should never see a VF without the "slave" > flag. > > > > This commit moves the code of setting the slave flag to the time > > before VF is exposed to user-mode. > > Can you give a real example in the commit message of a flow in user space > which would get confused by seeing the VF netdev without IFF_SLAVE? A user-mode program may see the VF netdev show up without SLAVE flag before seeing the NETVSC netdev. It may try to configure the VF before it will be bonded to a NETVSC. With the IFF_SLAVE correctly set at the time of VF showing up to the user-mode, it can rely on this flag to decide if this device should be ignored. (without implementing some timeout logic to detect a potential NETVSC device that may show up later) > > You're only moving setting IFF_SLAVE but not linking the master, is there no > code which would assume that if SLAVE is set there is a master? The same (taking IFF_SLAVE without linking to master) is done in the original code before VF is joined, but it was for another purpose. I think there is a gap between when the VF is acted upon by other parts of the system and when it's bonded.
