[PATCH] PCI: Fix pcibios_update_irq misuse of irq number

[Bjorn Helgaas]

On Wed, Jan 28, 2015 at 8:51 AM, Marc Zyngier <marc.zyngier at arm.com> wrote:
> pcibios_update_irq writes an irq number into the config space
> of a given PCI device, but ignores the fact that this number
> is a virtual interrupt number, which might be a very different
> value from what the underlying hardware is using.
>
> The obvious fix is to fetch the HW interrupt number from the
> corresponding irq_data structure. This is slightly complicated
> by the fact that this interrupt might be services by a stacked
> domain.
>
> This has been tested on KVM with kvmtool.
>
> Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> Tested-by: Andre Przywara <andre.przywara at arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>

Jiang, are you OK with this patch as-is now, since it isn't used on x86?

Marc, Lorenzo, I assume this actually fixes a bug.  Can we get any
more details about what happens when you hit the bug, and how you
reproduced it (what platform, driver, etc.)?

Bjorn

> ---
>  drivers/pci/setup-irq.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/setup-irq.c b/drivers/pci/setup-irq.c
> index 4e2d595..828cbc9 100644
> --- a/drivers/pci/setup-irq.c
> +++ b/drivers/pci/setup-irq.c
> @@ -15,11 +15,19 @@
>  #include <linux/errno.h>
>  #include <linux/ioport.h>
>  #include <linux/cache.h>
> +#include <linux/irq.h>
>
>  void __weak pcibios_update_irq(struct pci_dev *dev, int irq)
>  {
> -       dev_dbg(&dev->dev, "assigning IRQ %02d\n", irq);
> -       pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
> +       struct irq_data *d;
> +
> +       d = irq_get_irq_data(irq);
> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
> +       while (d->parent_data)
> +               d = d->parent_data;
> +#endif
> +       dev_dbg(&dev->dev, "assigning IRQ %02ld\n", d->hwirq);
> +       pci_write_config_byte(dev, PCI_INTERRUPT_LINE, d->hwirq);
>  }
>
>  static void pdev_fixup_irq(struct pci_dev *dev,
> --
> 2.1.4
>