linux-kernel - Re: msi_free

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Date:	Thu, 24 May 2007 16:11:12 -0500
From:	"Mike Miller (OS Dev)" <mikem@...rdog.cca.cpqcorp.net>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, tom.l.nguyen@...el.com,
	iss_storagedev@...com, jens.axboe@...cle.com,
	Michael Ellerman <michael@...erman.id.au>
Subject: Re: msi_free_irqs #2

On Thu, May 24, 2007 at 02:53:08PM -0600, Eric W. Biederman wrote:
> 
> 
> Could you please try the patch below.  Unless I have misread something
> this should fix your problem....
> 
> diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> index 000c9ae..2e1d4af 100644
> --- a/drivers/pci/msi.c
> +++ b/drivers/pci/msi.c
> @@ -404,7 +404,7 @@ static int msix_capability_init(struct pci_dev *dev,
>  		entry->dev = dev;
>  		entry->mask_base = base;
>  
> -		list_add(&entry->list, &dev->msi_list);
> +		list_add_tail(&entry->list, &dev->msi_list);
>  	}
>  
>  	ret = arch_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
> 
> > Michael or Eric, would you please review this patch and see if it's OK? Adding
> > an else
> > between the the if (list_is....) and the writel resolved the Oops. I'm not sure
> > how this
> > is supposed to work but using entry->mask_base after iounmap'ing seems wrong.
> 
> I think I would rather just swap those two lines of code.
> We are manually setting the mask bit to make certain the irq doesn't
> fire after we free it, and we clearly want to set the mask bit for
> all the irq entries.
> 
> > diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
> > index d9cbd58..0e67723 100644
> > --- a/drivers/pci/msi.c
> > +++ b/drivers/pci/msi.c
> > @@ -560,10 +560,11 @@ static int msi_free_irqs(struct pci_dev* dev)
> >  		if (entry->msi_attrib.type == PCI_CAP_ID_MSIX) {
> >  			if (list_is_last(&entry->list, &dev->msi_list))
> >  				iounmap(entry->mask_base);
> > -
> > -			writel(1, entry->mask_base + entry->msi_attrib.entry_nr
> > -				  * PCI_MSIX_ENTRY_SIZE
> > -				  + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
> > +			else
> > +				writel(1, entry->mask_base
> > +					+ entry->msi_attrib.entry_nr
> > +					* PCI_MSIX_ENTRY_SIZE
> > +					+ PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
> >  		}
> >  		list_del(&entry->list);
> >  		kfree(entry);

Here's a patch that just reverses the 2 lines of code as Eric suggests. Please
consider this for inclusion.

Signed-off-by: Mike Miller <mike.miller@...com>
Signed-off-by: Chase Maupin <chase.maupin@...com>

Thanks,
mikem
----------------------------------------------------------------------------------------
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index e01380b..6632150 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -558,12 +558,12 @@ static int msi_free_irqs(struct pci_dev* dev)
 
 	list_for_each_entry_safe(entry, tmp, &dev->msi_list, list) {
 		if (entry->msi_attrib.type == PCI_CAP_ID_MSIX) {
-			if (list_is_last(&entry->list, &dev->msi_list))
-				iounmap(entry->mask_base);
-
 			writel(1, entry->mask_base + entry->msi_attrib.entry_nr
 				  * PCI_MSIX_ENTRY_SIZE
 				  + PCI_MSIX_ENTRY_VECTOR_CTRL_OFFSET);
+
+			if (list_is_last(&entry->list, &dev->msi_list))
+				iounmap(entry->mask_base);
 		}
 		list_del(&entry->list);
 		kfree(entry);
-
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