xen: handled remapped IRQs when enabling a pcifront PCI device.

This happens to not be an issue currently because we take pains to try
to ensure that the GSI-IRQ mapping is 1-1 in a PV guest and that
regular event channels do not clash. However a subsequent patch is
going to break this 1-1 mapping.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>

1 files changed, 14 insertions, 8 deletions

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 25cd4a07d09f..2a12f3dbdd02 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -226,21 +226,27 @@ static int xen_pcifront_enable_irq(struct pci_dev *dev)
 {
         int rc;
         int share = 1;
+        u8 gsi;
 
-        dev_info(&dev->dev, "Xen PCI enabling IRQ: %d\n", dev->irq);
-
-        if (dev->irq < 0)
-                return -EINVAL;
+        rc = pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &gsi);
+        if (rc < 0) {
+                dev_warn(&dev->dev, "Xen PCI: failed to read interrupt line: %d\n",
+                         rc);
+                return rc;
+        }
 
-        if (dev->irq < NR_IRQS_LEGACY)
+        if (gsi < NR_IRQS_LEGACY)
                 share = 0;
 
-        rc = xen_allocate_pirq(dev->irq, share, "pcifront");
+        rc = xen_allocate_pirq(gsi, share, "pcifront");
         if (rc < 0) {
-                dev_warn(&dev->dev, "Xen PCI IRQ: %d, failed to register:%d\n",
-                         dev->irq, rc);
+                dev_warn(&dev->dev, "Xen PCI: failed to register GSI%d: %d\n",
+                         gsi, rc);
                 return rc;
         }
+
+        dev->irq = rc;
+        dev_info(&dev->dev, "Xen PCI mapped GSI%d to IRQ%d\n", gsi, dev->irq);
         return 0;
 }