[PATCH] net/mlx5: stop waiting for PCI link if reset is required

[PATCH] net/mlx5: stop waiting for PCI link if reset is required

[Niklas Schnelle]

after an error on the PCI link, the driver does not need to wait
for the link to become functional again as a reset is required. Stop
the wait loop in this case to accelerate the recovery flow.

Co-developed-by: Alexander Schmidt <alexs@linux.ibm.com>
Signed-off-by: Alexander Schmidt <alexs@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/health.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/health.c b/drivers/net/ethernet/mellanox/mlx5/core/health.c
index f9438d4e43ca..81ca44e0705a 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/health.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/health.c
@@ -325,6 +325,8 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
 	while (sensor_pci_not_working(dev)) {
 		if (time_after(jiffies, end))
 			return -ETIMEDOUT;
+		if (pci_channel_offline(dev->pdev))
+			return -EIO;
 		msleep(100);
 	}
 	return 0;
@@ -332,10 +334,16 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
 
 static int mlx5_health_try_recover(struct mlx5_core_dev *dev)
 {
+	int rc;
+
 	mlx5_core_warn(dev, "handling bad device here\n");
 	mlx5_handle_bad_state(dev);
-	if (mlx5_health_wait_pci_up(dev)) {
-		mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
+	rc = mlx5_health_wait_pci_up(dev);
+	if (rc) {
+		if (rc == -ETIMEDOUT)
+			mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
+		else
+			mlx5_core_err(dev, "health recovery flow aborted, PCI channel offline\n");
 		return -EIO;
 	}
 	mlx5_core_err(dev, "starting health recovery flow\n");

base-commit: 7e364e56293bb98cae1b55fd835f5991c4e96e7d
-- 
2.37.2

Re: [PATCH] net/mlx5: stop waiting for PCI link if reset is required

[Leon Romanovsky]

On Mon, Apr 03, 2023 at 09:56:56AM +0200, Niklas Schnelle wrote:
> after an error on the PCI link, the driver does not need to wait
> for the link to become functional again as a reset is required. Stop
> the wait loop in this case to accelerate the recovery flow.
> 
> Co-developed-by: Alexander Schmidt <alexs@linux.ibm.com>
> Signed-off-by: Alexander Schmidt <alexs@linux.ibm.com>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/health.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/health.c b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> index f9438d4e43ca..81ca44e0705a 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/health.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> @@ -325,6 +325,8 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
>  	while (sensor_pci_not_working(dev)) {

According to the comment in sensor_pci_not_working(), this loop is
supposed to wait till PCI will be ready again. Otherwise, already in
first iteration, we will bail out with pci_channel_offline() error.

Thanks

>  		if (time_after(jiffies, end))
>  			return -ETIMEDOUT;
> +		if (pci_channel_offline(dev->pdev))
> +			return -EIO;
>  		msleep(100);
>  	}
>  	return 0;
> @@ -332,10 +334,16 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
>  
>  static int mlx5_health_try_recover(struct mlx5_core_dev *dev)
>  {
> +	int rc;
> +
>  	mlx5_core_warn(dev, "handling bad device here\n");
>  	mlx5_handle_bad_state(dev);
> -	if (mlx5_health_wait_pci_up(dev)) {
> -		mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
> +	rc = mlx5_health_wait_pci_up(dev);
> +	if (rc) {
> +		if (rc == -ETIMEDOUT)
> +			mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
> +		else
> +			mlx5_core_err(dev, "health recovery flow aborted, PCI channel offline\n");
>  		return -EIO;
>  	}
>  	mlx5_core_err(dev, "starting health recovery flow\n");
> 
> base-commit: 7e364e56293bb98cae1b55fd835f5991c4e96e7d
> -- 
> 2.37.2
> 

Re: [PATCH] net/mlx5: stop waiting for PCI link if reset is required

[Niklas Schnelle]

On Mon, 2023-04-03 at 21:21 +0300, Leon Romanovsky wrote:
> On Mon, Apr 03, 2023 at 09:56:56AM +0200, Niklas Schnelle wrote:
> > after an error on the PCI link, the driver does not need to wait
> > for the link to become functional again as a reset is required. Stop
> > the wait loop in this case to accelerate the recovery flow.
> > 
> > Co-developed-by: Alexander Schmidt <alexs@linux.ibm.com>
> > Signed-off-by: Alexander Schmidt <alexs@linux.ibm.com>
> > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> > ---
> >  drivers/net/ethernet/mellanox/mlx5/core/health.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/health.c b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > index f9438d4e43ca..81ca44e0705a 100644
> > --- a/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > +++ b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > @@ -325,6 +325,8 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
> >  	while (sensor_pci_not_working(dev)) {
> 
> According to the comment in sensor_pci_not_working(), this loop is
> supposed to wait till PCI will be ready again. Otherwise, already in
> first iteration, we will bail out with pci_channel_offline() error.
> 
> Thanks

Well yes. The problem is that this works for intermittent errors
including when the card resets itself which seems to be the use case in
mlx5_fw_reset_complete_reload() and mlx5_devlink_reload_fw_activate().
If there is a PCI error that requires a link reset though we see some
problems though it does work after running into the timeout.

As I understand it and as implemented at least on s390,
pci_channel_io_frozen is only set for fatal errors that require a reset
while non fatal errors will have pci_channel_io_normal (see also
Documentation/PCI/pcieaer-howto.rst) thus I think pci_channel_offline()
should only be true if a reset is required or there is a permanent
error. Furthermore in the pci_channel_io_frozen state the PCI function
may be isolated and the reads will not reach the endpoint, this is the
case at least on s390.  Thus for errors requiring a reset the loop
without pci_channel_offline() will run until the reset is performed or
the timeout is reached. In the mlx5_health_try_recover() case during
error recovery we will then indeed always loop until timeout, because
the loop blocks mlx5_pci_err_detected() from returning thus blocking
the reset (see Documentation/PCI/pci-error-recovery.rst). Adding Bjorn,
maybe he can confirm or correct my assumptions here.

Thanks,
Niklas

> 
> >  		if (time_after(jiffies, end))
> >  			return -ETIMEDOUT;
> > +		if (pci_channel_offline(dev->pdev))
> > +			return -EIO;
> >  		msleep(100);
> >  	}
> >  	return 0;
> > @@ -332,10 +334,16 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
> >  
> >  static int mlx5_health_try_recover(struct mlx5_core_dev *dev)
> >  {
> > +	int rc;
> > +
> >  	mlx5_core_warn(dev, "handling bad device here\n");
> >  	mlx5_handle_bad_state(dev);
> > -	if (mlx5_health_wait_pci_up(dev)) {
> > -		mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
> > +	rc = mlx5_health_wait_pci_up(dev);
> > +	if (rc) {
> > +		if (rc == -ETIMEDOUT)
> > +			mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
> > +		else
> > +			mlx5_core_err(dev, "health recovery flow aborted, PCI channel offline\n");
> >  		return -EIO;
> >  	}
> >  	mlx5_core_err(dev, "starting health recovery flow\n");
> > 
> > base-commit: 7e364e56293bb98cae1b55fd835f5991c4e96e7d
> > -- 
> > 2.37.2
> > 

Re: [PATCH] net/mlx5: stop waiting for PCI link if reset is required

[Bjorn Helgaas]

On Tue, Apr 04, 2023 at 05:27:35PM +0200, Niklas Schnelle wrote:
> On Mon, 2023-04-03 at 21:21 +0300, Leon Romanovsky wrote:
> > On Mon, Apr 03, 2023 at 09:56:56AM +0200, Niklas Schnelle wrote:
> > > after an error on the PCI link, the driver does not need to wait
> > > for the link to become functional again as a reset is required. Stop
> > > the wait loop in this case to accelerate the recovery flow.
> > > 
> > > Co-developed-by: Alexander Schmidt <alexs@linux.ibm.com>
> > > Signed-off-by: Alexander Schmidt <alexs@linux.ibm.com>
> > > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> > > ---
> > >  drivers/net/ethernet/mellanox/mlx5/core/health.c | 12 ++++++++++--
> > >  1 file changed, 10 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/health.c b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > > index f9438d4e43ca..81ca44e0705a 100644
> > > --- a/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > > +++ b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > > @@ -325,6 +325,8 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
> > >  	while (sensor_pci_not_working(dev)) {
> > 
> > According to the comment in sensor_pci_not_working(), this loop is
> > supposed to wait till PCI will be ready again. Otherwise, already in
> > first iteration, we will bail out with pci_channel_offline() error.
> 
> Well yes. The problem is that this works for intermittent errors
> including when the card resets itself which seems to be the use case in
> mlx5_fw_reset_complete_reload() and mlx5_devlink_reload_fw_activate().
> If there is a PCI error that requires a link reset though we see some
> problems though it does work after running into the timeout.
> 
> As I understand it and as implemented at least on s390,
> pci_channel_io_frozen is only set for fatal errors that require a reset
> while non fatal errors will have pci_channel_io_normal (see also
> Documentation/PCI/pcieaer-howto.rst)

Yes, I think that's true, see handle_error_source().

> thus I think pci_channel_offline()
> should only be true if a reset is required or there is a permanent
> error.

Yes, I think pci_channel_offline() will only be true when a fatal
error has been reported via AER or DPC (or a hotplug driver says the
device has been removed).  The driver resetting the device should not
cause such a fatal error.

> Furthermore in the pci_channel_io_frozen state the PCI function
> may be isolated and the reads will not reach the endpoint, this is the
> case at least on s390.  Thus for errors requiring a reset the loop
> without pci_channel_offline() will run until the reset is performed or
> the timeout is reached. In the mlx5_health_try_recover() case during
> error recovery we will then indeed always loop until timeout, because
> the loop blocks mlx5_pci_err_detected() from returning thus blocking
> the reset (see Documentation/PCI/pci-error-recovery.rst). Adding Bjorn,
> maybe he can confirm or correct my assumptions here.

> > >  		if (time_after(jiffies, end))
> > >  			return -ETIMEDOUT;
> > > +		if (pci_channel_offline(dev->pdev))
> > > +			return -EIO;
> > >  		msleep(100);
> > >  	}
> > >  	return 0;
> > > @@ -332,10 +334,16 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
> > >  
> > >  static int mlx5_health_try_recover(struct mlx5_core_dev *dev)
> > >  {
> > > +	int rc;
> > > +
> > >  	mlx5_core_warn(dev, "handling bad device here\n");
> > >  	mlx5_handle_bad_state(dev);
> > > -	if (mlx5_health_wait_pci_up(dev)) {
> > > -		mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
> > > +	rc = mlx5_health_wait_pci_up(dev);
> > > +	if (rc) {
> > > +		if (rc == -ETIMEDOUT)
> > > +			mlx5_core_err(dev, "health recovery flow aborted, PCI reads still not working\n");
> > > +		else
> > > +			mlx5_core_err(dev, "health recovery flow aborted, PCI channel offline\n");
> > >  		return -EIO;
> > >  	}
> > >  	mlx5_core_err(dev, "starting health recovery flow\n");
> > > 
> > > base-commit: 7e364e56293bb98cae1b55fd835f5991c4e96e7d
> > > -- 
> > > 2.37.2
> > > 
> 

Re: [PATCH] net/mlx5: stop waiting for PCI link if reset is required

[Leon Romanovsky]

On Wed, Apr 05, 2023 at 04:06:13PM -0500, Bjorn Helgaas wrote:
> On Tue, Apr 04, 2023 at 05:27:35PM +0200, Niklas Schnelle wrote:
> > On Mon, 2023-04-03 at 21:21 +0300, Leon Romanovsky wrote:
> > > On Mon, Apr 03, 2023 at 09:56:56AM +0200, Niklas Schnelle wrote:
> > > > after an error on the PCI link, the driver does not need to wait
> > > > for the link to become functional again as a reset is required. Stop
> > > > the wait loop in this case to accelerate the recovery flow.
> > > > 
> > > > Co-developed-by: Alexander Schmidt <alexs@linux.ibm.com>
> > > > Signed-off-by: Alexander Schmidt <alexs@linux.ibm.com>
> > > > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> > > > ---
> > > >  drivers/net/ethernet/mellanox/mlx5/core/health.c | 12 ++++++++++--
> > > >  1 file changed, 10 insertions(+), 2 deletions(-)
> > > > 
> > > > diff --git a/drivers/net/ethernet/mellanox/mlx5/core/health.c b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > > > index f9438d4e43ca..81ca44e0705a 100644
> > > > --- a/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > > > +++ b/drivers/net/ethernet/mellanox/mlx5/core/health.c
> > > > @@ -325,6 +325,8 @@ int mlx5_health_wait_pci_up(struct mlx5_core_dev *dev)
> > > >  	while (sensor_pci_not_working(dev)) {
> > > 
> > > According to the comment in sensor_pci_not_working(), this loop is
> > > supposed to wait till PCI will be ready again. Otherwise, already in
> > > first iteration, we will bail out with pci_channel_offline() error.
> > 
> > Well yes. The problem is that this works for intermittent errors
> > including when the card resets itself which seems to be the use case in
> > mlx5_fw_reset_complete_reload() and mlx5_devlink_reload_fw_activate().
> > If there is a PCI error that requires a link reset though we see some
> > problems though it does work after running into the timeout.
> > 
> > As I understand it and as implemented at least on s390,
> > pci_channel_io_frozen is only set for fatal errors that require a reset
> > while non fatal errors will have pci_channel_io_normal (see also
> > Documentation/PCI/pcieaer-howto.rst)
> 
> Yes, I think that's true, see handle_error_source().
> 
> > thus I think pci_channel_offline()
> > should only be true if a reset is required or there is a permanent
> > error.
> 
> Yes, I think pci_channel_offline() will only be true when a fatal
> error has been reported via AER or DPC (or a hotplug driver says the
> device has been removed).  The driver resetting the device should not
> cause such a fatal error.

Thank you for an explanation and confirmation.

Re: [PATCH] net/mlx5: stop waiting for PCI link if reset is required

[Leon Romanovsky]

On Mon, Apr 03, 2023 at 09:56:56AM +0200, Niklas Schnelle wrote:
> after an error on the PCI link, the driver does not need to wait
> for the link to become functional again as a reset is required. Stop
> the wait loop in this case to accelerate the recovery flow.
> 
> Co-developed-by: Alexander Schmidt <alexs@linux.ibm.com>
> Signed-off-by: Alexander Schmidt <alexs@linux.ibm.com>
> Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/health.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 

The subject line should include target for netdev patches: [PATCH net-next] ....

Thanks,
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>

Re: [PATCH] net/mlx5: stop waiting for PCI link if reset is required

[Niklas Schnelle]

On Sun, 2023-04-09 at 11:55 +0300, Leon Romanovsky wrote:
> On Mon, Apr 03, 2023 at 09:56:56AM +0200, Niklas Schnelle wrote:
> > after an error on the PCI link, the driver does not need to wait
> > for the link to become functional again as a reset is required. Stop
> > the wait loop in this case to accelerate the recovery flow.
> > 
> > Co-developed-by: Alexander Schmidt <alexs@linux.ibm.com>
> > Signed-off-by: Alexander Schmidt <alexs@linux.ibm.com>
> > Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
> > ---
> >  drivers/net/ethernet/mellanox/mlx5/core/health.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> > 
> 
> The subject line should include target for netdev patches: [PATCH net-next] ....
> 
> Thanks,
> Reviewed-by: Leon Romanovsky <leonro@nvidia.com>

Thanks, I'll sent a v2 with your R-b, the correct net-next prefix and a
Link to this discussion.