Re: WARNING: CPU: 4 PID: 863 at include/drm/drm_crtc.h:1577 drm_helper_choose_encoder_dpms+0x88/0x90() - evildoer found and neutralized

[Borislav Petkov <bp@alien8.de>]

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;
+
 	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)
 		pcibios_disable_irq(dev);
 }
--

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.