Patchwork [RFC,50/77] mlx5: Update MSI/MSI-X interrupts enablement code

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Submitter Alexander Gordeev
Date Oct. 2, 2013, 10:49 a.m.
Message ID <9650a7dfbcfd5f1da21f7b093665abf4b1041071.1380703263.git.agordeev@redhat.com>
Download mbox | patch
Permalink /patch/279874/
State RFC
Headers show

Comments

Alexander Gordeev - Oct. 2, 2013, 10:49 a.m.
As result of recent re-design of the MSI/MSI-X interrupts enabling
pattern this driver has to be updated to use the new technique to
obtain a optimal number of MSI/MSI-X interrupts required.

Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/main.c |   18 +++++++++---------
 1 files changed, 9 insertions(+), 9 deletions(-)
Eli Cohen - Oct. 3, 2013, 7:14 a.m.
On Wed, Oct 02, 2013 at 12:49:06PM +0200, Alexander Gordeev wrote:
>  
> +	err = pci_msix_table_size(dev->pdev);
> +	if (err < 0)
> +		return err;
> +
>  	nvec = dev->caps.num_ports * num_online_cpus() + MLX5_EQ_VEC_COMP_BASE;
>  	nvec = min_t(int, nvec, num_eqs);
> +	nvec = min_t(int, nvec, err);
>  	if (nvec <= MLX5_EQ_VEC_COMP_BASE)
>  		return -ENOSPC;

Making sure we don't request more vectors then the device's is capable
of -- looks good.
>  
> @@ -131,20 +136,15 @@ static int mlx5_enable_msix(struct mlx5_core_dev *dev)
>  	for (i = 0; i < nvec; i++)
>  		table->msix_arr[i].entry = i;
>  
> -retry:
> -	table->num_comp_vectors = nvec - MLX5_EQ_VEC_COMP_BASE;
>  	err = pci_enable_msix(dev->pdev, table->msix_arr, nvec);
> -	if (err <= 0) {
> +	if (err) {
> +		kfree(table->msix_arr);
>  		return err;
> -	} else if (err > MLX5_EQ_VEC_COMP_BASE) {
> -		nvec = err;
> -		goto retry;
>  	}
>  

According to latest sources, pci_enable_msix() may still fail so why
do you want to remove this code?

> -	mlx5_core_dbg(dev, "received %d MSI vectors out of %d requested\n", err, nvec);
> -	kfree(table->msix_arr);
> +	table->num_comp_vectors = nvec - MLX5_EQ_VEC_COMP_BASE;
>  
> -	return -ENOSPC;
> +	return 0;
>  }
>  
>  static void mlx5_disable_msix(struct mlx5_core_dev *dev)
> -- 
> 1.7.7.6
> 
> --
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Alexander Gordeev - Oct. 3, 2013, 7:48 p.m.
On Thu, Oct 03, 2013 at 10:14:33AM +0300, Eli Cohen wrote:
> On Wed, Oct 02, 2013 at 12:49:06PM +0200, Alexander Gordeev wrote:
> >  
> > +	err = pci_msix_table_size(dev->pdev);
> > +	if (err < 0)
> > +		return err;
> > +
> >  	nvec = dev->caps.num_ports * num_online_cpus() + MLX5_EQ_VEC_COMP_BASE;
> >  	nvec = min_t(int, nvec, num_eqs);
> > +	nvec = min_t(int, nvec, err);
> >  	if (nvec <= MLX5_EQ_VEC_COMP_BASE)
> >  		return -ENOSPC;
> 
> Making sure we don't request more vectors then the device's is capable
> of -- looks good.
> >  
> > @@ -131,20 +136,15 @@ static int mlx5_enable_msix(struct mlx5_core_dev *dev)
> >  	for (i = 0; i < nvec; i++)
> >  		table->msix_arr[i].entry = i;
> >  
> > -retry:
> > -	table->num_comp_vectors = nvec - MLX5_EQ_VEC_COMP_BASE;
> >  	err = pci_enable_msix(dev->pdev, table->msix_arr, nvec);
> > -	if (err <= 0) {
> > +	if (err) {
> > +		kfree(table->msix_arr);
> >  		return err;
> > -	} else if (err > MLX5_EQ_VEC_COMP_BASE) {
> > -		nvec = err;
> > -		goto retry;
> >  	}
> >  
> 
> According to latest sources, pci_enable_msix() may still fail so why
> do you want to remove this code?

pci_enable_msix() may fail, but it can not return a positive number.

We first calculate how many MSI-Xs we need, adjust to what we can get,
check if that is enough and only then go for it.

> > -	mlx5_core_dbg(dev, "received %d MSI vectors out of %d requested\n", err, nvec);
> > -	kfree(table->msix_arr);
> > +	table->num_comp_vectors = nvec - MLX5_EQ_VEC_COMP_BASE;
> >  
> > -	return -ENOSPC;
> > +	return 0;
> >  }
> >  
> >  static void mlx5_disable_msix(struct mlx5_core_dev *dev)
Eli Cohen - Oct. 10, 2013, 3:29 p.m.
On Thu, Oct 03, 2013 at 09:48:39PM +0200, Alexander Gordeev wrote:
> 
> pci_enable_msix() may fail, but it can not return a positive number.
>

That is true according to the current logic but the comment on top of
pci_enable_msix() still says:
"A return of < 0 indicates a failure.  Or a return of > 0 indicates
that driver request is exceeding the number of irqs or MSI-X vectors
available"

So you're counting on an implementation that may change in the future.
I think leaving the code as it is now is safer.
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Patch

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/main.c b/drivers/net/ethernet/mellanox/mlx5/core/main.c
index adf0e5d..5c21e50 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/main.c
@@ -119,8 +119,13 @@  static int mlx5_enable_msix(struct mlx5_core_dev *dev)
 	int err;
 	int i;
 
+	err = pci_msix_table_size(dev->pdev);
+	if (err < 0)
+		return err;
+
 	nvec = dev->caps.num_ports * num_online_cpus() + MLX5_EQ_VEC_COMP_BASE;
 	nvec = min_t(int, nvec, num_eqs);
+	nvec = min_t(int, nvec, err);
 	if (nvec <= MLX5_EQ_VEC_COMP_BASE)
 		return -ENOSPC;
 
@@ -131,20 +136,15 @@  static int mlx5_enable_msix(struct mlx5_core_dev *dev)
 	for (i = 0; i < nvec; i++)
 		table->msix_arr[i].entry = i;
 
-retry:
-	table->num_comp_vectors = nvec - MLX5_EQ_VEC_COMP_BASE;
 	err = pci_enable_msix(dev->pdev, table->msix_arr, nvec);
-	if (err <= 0) {
+	if (err) {
+		kfree(table->msix_arr);
 		return err;
-	} else if (err > MLX5_EQ_VEC_COMP_BASE) {
-		nvec = err;
-		goto retry;
 	}
 
-	mlx5_core_dbg(dev, "received %d MSI vectors out of %d requested\n", err, nvec);
-	kfree(table->msix_arr);
+	table->num_comp_vectors = nvec - MLX5_EQ_VEC_COMP_BASE;
 
-	return -ENOSPC;
+	return 0;
 }
 
 static void mlx5_disable_msix(struct mlx5_core_dev *dev)