From: Andrew Morton <akpm@osdl.org>

Rajesh Shah <rajesh.shah@intel.com> wrote:

> A driver that calls pci_enable_msi() while MSI is already enabled
> will hit this BUG_ON. This is different from the behavior of
> some other pci functions like pci_enable_device(), which
> silently return success if the requested operation is a nop.
> It's pretty easy to do the same here too (ditto for MSI-X).

Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rajesh Shah <rajesh.shah@intel.com>
Cc: Andi Kleen <ak@muc.de>
Cc: "Protasevich, Natalie" <Natalie.Protasevich@UNISYS.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---

 drivers/pci/msi.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff -puN drivers/pci/msi.c~genirq-msi-simplify-msi-enable-and-disable-fix drivers/pci/msi.c
--- a/drivers/pci/msi.c~genirq-msi-simplify-msi-enable-and-disable-fix
+++ a/drivers/pci/msi.c
@@ -947,7 +947,7 @@ int pci_enable_msi(struct pci_dev* dev)
 	if (!pos)
 		return -EINVAL;
 
-	BUG_ON(!msi_lookup_vector(dev, PCI_CAP_ID_MSI));
+	WARN_ON(!msi_lookup_vector(dev, PCI_CAP_ID_MSI));
 
 	/* Check whether driver already requested for MSI-X vectors */
 	pos = pci_find_capability(dev, PCI_CAP_ID_MSIX);
@@ -1106,7 +1106,7 @@ int pci_enable_msix(struct pci_dev* dev,
 		}
 	}
 	temp = dev->irq;
-	BUG_ON(!msi_lookup_vector(dev, PCI_CAP_ID_MSIX));
+	WARN_ON(!msi_lookup_vector(dev, PCI_CAP_ID_MSIX));
 
 	/* Check whether driver already requested for MSI vector */
    	if (pci_find_capability(dev, PCI_CAP_ID_MSI) > 0 &&
_