On 2015/10/1 1:36, Borislav Petkov wrote:
> On Thu, Oct 01, 2015 at 01:00:44AM +0800, Jiang Liu wrote:
>> Thanks Joerg, that makes sense. If some driver tries to binding to
>> the IOMMU device, it will trigger the scenario as you described. For
>> example, Xen backend driver will try to probe all PCI devices if
>> enabled. I will do more investigation tomorrow.
>
> Right, so this fixes the issue on my box, courtesy of Joerg. WE
> basically don't disable the IRQ on MSI-enabled devices. The AMD IOMMU
> uses a barebones PCI device but not a PCI driver, which would be an
> overkill.
>
> ---
> diff --git a/arch/x86/pci/common.c b/arch/x86/pci/common.c
> index 09d3afc..29ec2eb 100644
> --- a/arch/x86/pci/common.c
> +++ b/arch/x86/pci/common.c
> @@ -674,12 +674,15 @@ int pcibios_add_device(struct pci_dev *dev)
>
> int pcibios_alloc_irq(struct pci_dev *dev)
> {
> + if (pci_dev_msi_enabled(dev))
> + return 0;
We may return -EBUSY here to reject the probe operation. It
doesn't make sense to continue the probe if MSI is already enabled,
tt also helps to avoid calling pcibios_free_irq() in function
pci_device_probe().
> +
> return pcibios_enable_irq(dev);
> }
>
> void pcibios_free_irq(struct pci_dev *dev)
> {
> - if (pcibios_disable_irq)
> + if (!pci_dev_msi_enabled(dev) && pcibios_disable_irq)
The above change is not needed, pcibios_disable_irq() will
first check !pci_has_managed_irq(dev) before actually freeing
PCI irq. pci_has_managed_irq(dev) only returns true if
pcibios_alloc_irq() succeeds.
So to summary, I think we only need following change to fix the
regression:
int pcibios_alloc_irq(struct pci_dev *dev)
{
+ if (pci_dev_msi_enabled(dev))
+ return -EBUSY;
What do you think?
Thanks!
Gerry
> pcibios_disable_irq(dev);
> }
> --
>
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