[Xen-devel] [PATCH 1/4] xen: handled remapped IRQs when enabling a pcifront PCI device.

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

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@xxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
---
 arch/x86/pci/xen.c |   22 ++++++++++++++--------
 1 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 25cd4a0..2a12f3d 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;
 }
 
-- 
1.5.6.5


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