>Subject: Re: [dpdk-dev] [PATCH] net/vdev_netvsc: handle removal of >associated pci device > >Hi Stephen > >From: Stephen Hemminger: >> On Sun, 6 Sep 2020 12:38:18 +0000 >> Matan Azrad <ma...@nvidia.com> wrote: >> >> > Hi Stephen >> > >> > From: Stephen Hemminger: >> > > The vdev_netvsc was not detecting when the associated PCI device >> > > (SRIOV) was removed. Because of that it would keep feeding the >> > > same >> > > (removed) device to failsafe PMD which would then unsuccessfully >> > > try and probe for it. >> > > >> > > Change to use a mark/sweep method to detect that PCI device was >> > > removed, and also only tell failsafe about new PCI devices. >> > > Vdev_netvsc does not have to keep stuffing the pipe with the same >> > > already existing PCI device. >> > >> > As I know, the vdev_netvsc driver doesn't call to failsafe if the >> > PCI device is >> not detected by the readlink command(considered as removed)... >> > Am I missing something? >> >> The original code is broken because ctx_yield is not cleared, it keeps >> sending the same value. > >Looking on the code again, It looks like ctx->yield has no effect on the next >pipe write, It is just used for log. > >After the PCI interface matching to the netvsc interface, the pipe write is >triggered only if the readlink commands success to see the plugged-in PCI >device: >readlink /sys/class/net/[iface]/device/subsystem shows "pci" >readlink /sys/class/net/[iface]/device shows the pci device ID. > >So, the assumption is when the above readlink failed on the interface the >device is removed(plugged-out) and the fd write will not happen. > >The code will continue to retry probe again and again until success only for >plugged-in pci device matched the netvsc device.
Hi Matan, The original code keeps writing to pipe even it's the same PCI device. The new code writes to pipe for a new device, only once. See the following code: + /* Skip if this is same device already sent to failsafe */ + if (strcmp(addr, ctx->yield) == 0) + return 0; This patch also saves lots of CPU since it no longer writes to pipe all the time. You are correct about the code will continue to probe on a new PCI device. But someone has to do it to handle hot-add. Thanks, Long > >> It looks like device removal and add was never tested. > >This is basic test we have to test plug-in plug-out and it passed every day in >the last years. > >Maybe something new and special in your setup? > >> If you test removal you will see that vdev_netvsc: >> 1. Sends same PCI device repeatedly to failsafe (every alarm call) >> This is harmless, but useless. >> 2. When device is removed, keeps doing #1
