Re: [Qemu-devel] [PATCH] pci: Don't call pci_irq_handler() for a negative intx

[Michael S. Tsirkin]

On Sun, Jul 05, 2015 at 09:28:28AM +1000, Benjamin Herrenschmidt wrote:
> Under some circumstances, pci_intx() can return -1 (when the interrupt
> pin in the config space is 0 which normally means no interrupt).
> 
> I have seen cases of pci_set_irq() being called on such devices, in
> turn causing pci_irq_handler() to be called with "-1" as an argument
> which doesn't seem like a terribly good idea.
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>

Isn't this a device bug though?

I did a grep over all callers of pci_set_irq and didn't
find any that fails to set an interrupt pin.

So how about an assert instead?

And maybe stick it in pci_intx to make sure all callers
get checked.

> ---
>  hw/pci/pci.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> index 8185bbc..eea6f5d 100644
> --- a/hw/pci/pci.c
> +++ b/hw/pci/pci.c
> @@ -1281,7 +1281,9 @@ qemu_irq pci_allocate_irq(PCIDevice *pci_dev)
>  void pci_set_irq(PCIDevice *pci_dev, int level)
>  {
>      int intx = pci_intx(pci_dev);
> -    pci_irq_handler(pci_dev, intx, level);
> +    if (intx >= 0) {
> +        pci_irq_handler(pci_dev, intx, level);
> +    }
>  }
>  
>  /* Special hooks used by device assignment */
>