Date: Wed, 19 Feb 2014 20:22:55 +0100
From: Alexander Gordeev <agordeev@redhat.com>
To: Jon Mason <jon.mason@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [PATCH] ntb: Use pci_enable_msix_range() instead of
 pci_enable_msix()
Message-ID: <20140219192255.GA20609@dhcp-26-207.brq.redhat.com>
References: <1392804931-30671-1-git-send-email-agordeev@redhat.com>
 <20140219180926.GA1333@jonmason-lab>
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On Wed, Feb 19, 2014 at 11:09:27AM -0700, Jon Mason wrote:
> > diff --git a/drivers/ntb/ntb_hw.c b/drivers/ntb/ntb_hw.c
> > index 170e8e6..fda37eb 100644
> > --- a/drivers/ntb/ntb_hw.c
> > +++ b/drivers/ntb/ntb_hw.c
> > @@ -1085,21 +1085,15 @@ static int ntb_setup_msix(struct ntb_device *ndev)
> >  	struct msix_entry *msix;
> >  	int msix_entries;
> >  	int rc, i;
> > -	u16 val;
> >  
> > -	if (!pdev->msix_cap) {
> > -		rc = -EIO;
> > -		goto err;
> > -	}
> > -
> > -	rc = pci_read_config_word(pdev, pdev->msix_cap + PCI_MSIX_FLAGS, &val);
> > -	if (rc)
> > +	rc = pci_msix_vec_count(pdev);
> 
> Nit, you should probably use msix_entries instead of rc in this case.

This way it resembles the code few lines below, so the style looks more
consistent. Whichever you wish, though ;)

> > +	if (rc < 0) {
> >  		goto err;
> > -
> > -	msix_entries = msix_table_size(val);
> > -	if (msix_entries > ndev->limits.msix_cnt) {
> > +	} else if (rc > ndev->limits.msix_cnt) {
> >  		rc = -EINVAL;
> >  		goto err;
> > +	} else {
> > +		msix_entries = rc;
> >  	}
> 
> Style Nit.  Braces with only one line.  If you make the change above,
> then it is moot.

Not on the top of my head, but do we mix bracing this way?

> >  
> >  	ndev->msix_entries = kmalloc(sizeof(struct msix_entry) * msix_entries,
> > @@ -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.

Well, I can re-post with a separate fix with this condition updated...

	} else if (rc < 2 || rc > ndev->limits.msix_cnt) {
		rc = -EINVAL;
		goto err;
	}

...and the original patch with call to pci_enable_msix_range( ...,
2, ndev->limits.msix_cnt)

Will it work with both BWD_HW and non-BWD_HW hardware?

> Thanks,
> Jon
> 
> 
> > +	if (rc < 0)
> > +		goto err1;
> > +	else if (rc < msix_entries) {
> > +		dev_warn(&pdev->dev, "Only %d MSI-X vectors. "
> > +			 "Limiting the number of queues to that number.\n", rc);
> >  		msix_entries = rc;
> > -
> > -		rc = pci_enable_msix(pdev, ndev->msix_entries, msix_entries);
> > -		if (rc)
> > -			goto err1;
> >  	}
> >  
> >  	for (i = 0; i < msix_entries; i++) {
> > diff --git a/drivers/ntb/ntb_hw.h b/drivers/ntb/ntb_hw.h
> > index bbdb7ed..d307107 100644
> > --- a/drivers/ntb/ntb_hw.h
> > +++ b/drivers/ntb/ntb_hw.h
> > @@ -60,8 +60,6 @@
> >  #define PCI_DEVICE_ID_INTEL_NTB_SS_HSX		0x2F0F
> >  #define PCI_DEVICE_ID_INTEL_NTB_B2B_BWD		0x0C4E
> >  
> > -#define msix_table_size(control)	((control & PCI_MSIX_FLAGS_QSIZE)+1)
> > -
> >  #ifndef readq
> >  static inline u64 readq(void __iomem *addr)
> >  {
> > -- 
> > 1.7.7.6
> > 

-- 
Regards,
Alexander Gordeev
agordeev@redhat.com
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