Patchwork [RFC,46/77] mlx4: Update MSI/MSI-X interrupts enablement code

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Submitter Alexander Gordeev
Date Oct. 2, 2013, 10:49 a.m.
Message ID <b0a9f6f455aa03b7769e6d9cc2e7fdbc06732b2f.1380703263.git.agordeev@redhat.com>
Download mbox | patch
Permalink /patch/279835/
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/mlx4/main.c |   17 ++++++++---------
 1 files changed, 8 insertions(+), 9 deletions(-)
Jack Morgenstein - Oct. 3, 2013, 8:02 a.m.
On Wed,  2 Oct 2013 12:49:02 +0200
Alexander Gordeev <agordeev@redhat.com> wrote:

NACK.  This change does not do anything logically as far as I can tell.
pci_enable_msix in the current upstream kernel itself calls
pci_msix_table_size.  The current code yields the same results
as the code suggested below. (i.e., the suggested code has no effect on
optimality).

BTW, pci_msix_table_size never returns a value < 0 (if msix is not
enabled, it returns 0 for the table size), so the (err < 0) check here
is not correct. (I also do not like using "err" here anyway for the
value returned by pci_msix_table_size().  There is no error here, and
it is simply confusing.

-Jack

> 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/mlx4/main.c |   17 ++++++++---------
>  1 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c
> b/drivers/net/ethernet/mellanox/mlx4/main.c index 60c9f4f..377a5ea
> 100644 --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -1852,8 +1852,16 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) int i;
>  
>  	if (msi_x) {
> +		err = pci_msix_table_size(dev->pdev);
> +		if (err < 0)
> +			goto no_msi;
> +
> +		/* Try if at least 2 vectors are available */
>  		nreq = min_t(int, dev->caps.num_eqs -
> dev->caps.reserved_eqs, nreq);
> +		nreq = min_t(int, nreq, err);
> +		if (nreq < 2)
> +			goto no_msi;
>  
>  		entries = kcalloc(nreq, sizeof *entries, GFP_KERNEL);
>  		if (!entries)
> @@ -1862,17 +1870,8 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) for (i = 0; i < nreq; ++i)
>  			entries[i].entry = i;
>  
> -	retry:
>  		err = pci_enable_msix(dev->pdev, entries, nreq);
>  		if (err) {
> -			/* Try again if at least 2 vectors are
> available */
> -			if (err > 1) {
> -				mlx4_info(dev, "Requested %d
> vectors, "
> -					  "but only %d MSI-X vectors
> available, "
> -					  "trying again\n", nreq,
> err);
> -				nreq = err;
> -				goto retry;
> -			}
>  			kfree(entries);
>  			goto no_msi;
>  		}

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Jack Morgenstein - Oct. 3, 2013, 8:27 a.m.
On Wed,  2 Oct 2013 12:49:02 +0200
Alexander Gordeev <agordeev@redhat.com> wrote:

UPDATING THIS REPLY.
Your change log confused me. The change below is not from a "recent
re-design", it is required due to an earlier patch in this patch set.
From the log, I assumed that the change you are talking about is already
upstream.

I will re-review.

-Jack

NACK.  This change does not do anything logically as far as I can tell.
pci_enable_msix in the current upstream kernel itself calls
pci_msix_table_size.  The current code yields the same resultswill
as the code suggested below. (i.e., the suggested code has no effect on
optimality).

BTW, pci_msix_table_size never returns a value < 0 (if msix is not
enabled, it returns 0 for the table size), so the (err < 0) check here
is not correct. (I also do not like using "err" here anyway for the
value returned by pci_msix_table_size().  There is no error here, and
it is simply confusing.

-Jack

> 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/mlx4/main.c |   17 ++++++++---------
>  1 files changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c
> b/drivers/net/ethernet/mellanox/mlx4/main.c index 60c9f4f..377a5ea
> 100644 --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> @@ -1852,8 +1852,16 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) int i;
>  
>  	if (msi_x) {
> +		err = pci_msix_table_size(dev->pdev);
> +		if (err < 0)
> +			goto no_msi;
> +
> +		/* Try if at least 2 vectors are available */
>  		nreq = min_t(int, dev->caps.num_eqs -
> dev->caps.reserved_eqs, nreq);
> +		nreq = min_t(int, nreq, err);
> +		if (nreq < 2)
> +			goto no_msi;
>  
>  		entries = kcalloc(nreq, sizeof *entries, GFP_KERNEL);
>  		if (!entries)
> @@ -1862,17 +1870,8 @@ static void mlx4_enable_msi_x(struct mlx4_dev
> *dev) for (i = 0; i < nreq; ++i)
>  			entries[i].entry = i;
>  
> -	retry:
>  		err = pci_enable_msix(dev->pdev, entries, nreq);
>  		if (err) {
> -			/* Try again if at least 2 vectors are
> available */
> -			if (err > 1) {
> -				mlx4_info(dev, "Requested %d
> vectors, "
> -					  "but only %d MSI-X vectors
> available, "
> -					  "trying again\n", nreq,
> err);
> -				nreq = err;
> -				goto retry;
> -			}
>  			kfree(entries);
>  			goto no_msi;
>  		}

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Jack Morgenstein - Oct. 3, 2013, 8:39 a.m.
On Wed,  2 Oct 2013 12:49:02 +0200
Alexander Gordeev <agordeev@redhat.com> wrote:

> 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>

New review -- ACK (i.e., patch is OK), subject to acceptance of patches
05 and 07 of this patch set.

I sent my previous review (NACK) when I was not yet aware that
changes proposed were due to the two earlier patches (mentioned above)
in the current patch set.

The change log here should actually read something like the following:

As a result of changes to the MSI/MSI_X enabling procedures, this driver
must be modified in order to preserve its current msi/msi_x enablement
logic.

-Jack
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Patch

diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
index 60c9f4f..377a5ea 100644
--- a/drivers/net/ethernet/mellanox/mlx4/main.c
+++ b/drivers/net/ethernet/mellanox/mlx4/main.c
@@ -1852,8 +1852,16 @@  static void mlx4_enable_msi_x(struct mlx4_dev *dev)
 	int i;
 
 	if (msi_x) {
+		err = pci_msix_table_size(dev->pdev);
+		if (err < 0)
+			goto no_msi;
+
+		/* Try if at least 2 vectors are available */
 		nreq = min_t(int, dev->caps.num_eqs - dev->caps.reserved_eqs,
 			     nreq);
+		nreq = min_t(int, nreq, err);
+		if (nreq < 2)
+			goto no_msi;
 
 		entries = kcalloc(nreq, sizeof *entries, GFP_KERNEL);
 		if (!entries)
@@ -1862,17 +1870,8 @@  static void mlx4_enable_msi_x(struct mlx4_dev *dev)
 		for (i = 0; i < nreq; ++i)
 			entries[i].entry = i;
 
-	retry:
 		err = pci_enable_msix(dev->pdev, entries, nreq);
 		if (err) {
-			/* Try again if at least 2 vectors are available */
-			if (err > 1) {
-				mlx4_info(dev, "Requested %d vectors, "
-					  "but only %d MSI-X vectors available, "
-					  "trying again\n", nreq, err);
-				nreq = err;
-				goto retry;
-			}
 			kfree(entries);
 			goto no_msi;
 		}