linux-kernel - Re: [PATCH] ntb: Use pci_enable_msix_range() instead of pci_enable

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Date:	Thu, 20 Feb 2014 14:22:58 +0100
From:	Alexander Gordeev <agordeev@...hat.com>
To:	Jon Mason <jon.mason@...el.com>
Cc:	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] ntb: Use pci_enable_msix_range() instead of
 pci_enable_msix()

On Wed, Feb 19, 2014 at 11:09:27AM -0700, Jon Mason wrote:
> On Wed, Feb 19, 2014 at 11:15:21AM +0100, Alexander Gordeev wrote:
> > @@ -1112,26 +1106,21 @@ static int ntb_setup_msix(struct ntb_device *ndev)
> >  	for (i = 0; i < msix_entries; i++)
> >  		ndev->msix_entries[i].entry = i;
> >  
> > -	rc = pci_enable_msix(pdev, ndev->msix_entries, msix_entries);
> > -	if (rc < 0)
> > -		goto err1;
> > -	if (rc > 0) {
> > +	if (ndev->hw_type != BWD_HW)
> >  		/* On SNB, the link interrupt is always tied to 4th vector.  If
> >  		 * we can't get all 4, then we can't use MSI-X.
> >  		 */
> > -		if (ndev->hw_type != BWD_HW) {
> > -			rc = -EIO;
> > -			goto err1;
> > -		}
> > -
> > -		dev_warn(&pdev->dev,
> > -			 "Only %d MSI-X vectors.  Limiting the number of queues to that number.\n",
> > -			 rc);
> > +		rc = pci_enable_msix_range(pdev, ndev->msix_entries,
> > +					   msix_entries, msix_entries);
> > +	else
> > +		rc = pci_enable_msix_range(pdev, ndev->msix_entries,
> > +					   1, msix_entries);
> 
> Actually, this must be 2 for the min.  One for the Data and one for
> the Link.  If you look a few lines after this in the original code,
> there is a grabbing of the last vector for the link.  I realize there
> is currently no check for this in the driver and a potential error
> case occurs.  I can make a separate patch to correct this issue if
> this patch is not going through my tree.

I am confused here again. In the original code I see "ntb-callback-msix"
is requested for all MSI-Xs on BWD_HW and "ntb-event-msix" requested for
the last vector on SNB_HW. Therefore, the range [1..msix_entries] should
be fine for BWD_HW, isn't it?

> Thanks,
> Jon

-- 
Regards,
Alexander Gordeev
agordeev@...hat.com
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