NAK: [SRU][Yakkety][PATCH 1/1] net/mlx4_core: Avoid delays during VF driver device shutdown

Thadeu Lima de Souza Cascardo cascardo at canonical.com
Mon Apr 3 13:32:46 UTC 2017


On Mon, Apr 03, 2017 at 05:11:34AM -0700, Joshua R. Poulson wrote:
> We're engaged to test the driver in the intended scenario and code
> path. We have a stable repro for the bug that this fixes.
> 
> Thanks, --jrp
> 

Is that on Yakkety, with this Yakkety backport as is?

I am more concerned about the paths that would use SHUTDOWN, have you tested
these as well?

Thanks.
Cascardo.

> On Mon, Apr 3, 2017 at 2:26 AM, Thadeu Lima de Souza Cascardo
> <cascardo at canonical.com> wrote:
> > On Thu, Mar 30, 2017 at 04:35:59PM -0400, Joseph Salisbury wrote:
> >> From: Jack Morgenstein <jackm at dev.mellanox.co.il>
> >>
> >> BugLink: http://bugs.launchpad.net/bugs/1672785
> >>
> >> Some Hypervisors detach VFs from VMs by instantly causing an FLR event
> >> to be generated for a VF.
> >>
> >> In the mlx4 case, this will cause that VF's comm channel to be disabled
> >> before the VM has an opportunity to invoke the VF device's "shutdown"
> >> method.
> >>
> >> For such Hypervisors, there is a race condition between the VF's
> >> shutdown method and its internal-error detection/reset thread.
> >>
> >> The internal-error detection/reset thread (which runs every 5 seconds) also
> >> detects a disabled comm channel. If the internal-error detection/reset
> >> flow wins the race, we still get delays (while that flow tries repeatedly
> >> to detect comm-channel recovery).
> >>
> >> The cited commit fixed the command timeout problem when the
> >> internal-error detection/reset flow loses the race.
> >>
> >> This commit avoids the unneeded delays when the internal-error
> >> detection/reset flow wins.
> >>
> >> Fixes: d585df1c5ccf ("net/mlx4_core: Avoid command timeouts during VF driver device shutdown")
> >> Signed-off-by: Jack Morgenstein <jackm at dev.mellanox.co.il>
> >> Reported-by: Simon Xiao <sixiao at microsoft.com>
> >> Signed-off-by: Tariq Toukan <tariqt at mellanox.com>
> >> Signed-off-by: David S. Miller <davem at davemloft.net>
> >> (backported from commit 4cbe4dac82e423ecc9a0ba46af24a860853259f4)
> >> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
> >> ---
> >>  drivers/net/ethernet/mellanox/mlx4/cmd.c  | 11 +++++++++++
> >>  drivers/net/ethernet/mellanox/mlx4/main.c | 11 +++++++++++
> >>  include/linux/mlx4/device.h               |  1 +
> >>  3 files changed, 23 insertions(+)
> >>
> >> diff --git a/drivers/net/ethernet/mellanox/mlx4/cmd.c b/drivers/net/ethernet/mellanox/mlx4/cmd.c
> >> index f04a423..be6906b 100644
> >> --- a/drivers/net/ethernet/mellanox/mlx4/cmd.c
> >> +++ b/drivers/net/ethernet/mellanox/mlx4/cmd.c
> >> @@ -2278,6 +2278,17 @@ static int sync_toggles(struct mlx4_dev *dev)
> >>               rd_toggle = swab32(readl(&priv->mfunc.comm->slave_read));
> >>               if (wr_toggle == 0xffffffff || rd_toggle == 0xffffffff) {
> >>                       /* PCI might be offline */
> >> +
> >> +                     /* If device removal has been requested,
> >> +                      * do not continue retrying.
> >> +                      */
> >> +                     if (dev->persist->interface_state &
> >> +                         MLX4_INTERFACE_STATE_NOWAIT) {
> >> +                             mlx4_warn(dev,
> >> +                                       "communication channel is offline\n");
> >> +                             return -EIO;
> >> +                     }
> >> +
> >>                       msleep(100);
> >>                       wr_toggle = swab32(readl(&priv->mfunc.comm->
> >>                                          slave_write));
> >> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
> >> index 7183ac4..ea5e362 100644
> >> --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> >> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> >> @@ -1916,6 +1916,14 @@ static int mlx4_comm_check_offline(struct mlx4_dev *dev)
> >>                              (u32)(1 << COMM_CHAN_OFFLINE_OFFSET));
> >>               if (!offline_bit)
> >>                       return 0;
> >> +
> >> +             /* If device removal has been requested,
> >> +              * do not continue retrying.
> >> +              */
> >> +             if (dev->persist->interface_state &
> >> +                 MLX4_INTERFACE_STATE_NOWAIT)
> >> +                     break;
> >> +
> >>               /* There are cases as part of AER/Reset flow that PF needs
> >>                * around 100 msec to load. We therefore sleep for 100 msec
> >>                * to allow other tasks to make use of that CPU during this
> >> @@ -3930,6 +3938,9 @@ static void mlx4_remove_one(struct pci_dev *pdev)
> >>       struct devlink *devlink = priv_to_devlink(priv);
> >>       int active_vfs = 0;
> >>
> >> +     if (mlx4_is_slave(dev))
> >> +             persist->interface_state |= MLX4_INTERFACE_STATE_NOWAIT;
> >> +
> >>       mutex_lock(&persist->interface_state_mutex);
> >>       persist->interface_state |= MLX4_INTERFACE_STATE_DELETION;
> >>       mutex_unlock(&persist->interface_state_mutex);
> >> diff --git a/include/linux/mlx4/device.h b/include/linux/mlx4/device.h
> >> index 42da355..d49f11d 100644
> >> --- a/include/linux/mlx4/device.h
> >> +++ b/include/linux/mlx4/device.h
> >> @@ -468,6 +468,7 @@ enum {
> >>       MLX4_INTERFACE_STATE_UP         = 1 << 0,
> >>       MLX4_INTERFACE_STATE_DELETION   = 1 << 1,
> >>       MLX4_INTERFACE_STATE_SHUTDOWN   = 1 << 2,
> >> +     MLX4_INTERFACE_STATE_NOWAIT     = 1 << 2,
> >
> > So, NOWAIT and SHUTDOWN are defined to the same value, so it might be
> > necessary to review it that is going to work as expected. Maybe doing
> > the shutdown removal is a path to consider (commit
> > b4353708f5a1c084fd73f1b6fd243b142157b173).
> >
> > Cascardo.
> >
> >>  };
> >>
> >>  #define MSTR_SM_CHANGE_MASK (MLX4_EQ_PORT_INFO_MSTR_SM_SL_CHANGE_MASK | \
> >> --
> >> 2.7.4
> >>
> >>
> >> --
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> >> kernel-team at lists.ubuntu.com
> >> https://lists.ubuntu.com/mailman/listinfo/kernel-team
> >
> > --
> > kernel-team mailing list
> > kernel-team at lists.ubuntu.com
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