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Date: Wed, 30 Sep 2015 19:36:19 +0200
From: Borislav Petkov <bp@alien8.de>
To: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Joerg Roedel <joro@8bytes.org>, Daniel Vetter <daniel@ffwll.ch>,
        Thomas Gleixner <tglx@linutronix.de>,
        Bjorn Helgaas <bhelgaas@google.com>,
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        Christian =?utf-8?B?S8O2bmln?= <christian.koenig@amd.com>,
        Maling list - DRI developers 
	<dri-devel@lists.freedesktop.org>,
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Subject: Re: WARNING: CPU: 4 PID: 863 at include/drm/drm_crtc.h:1577
 drm_helper_choose_encoder_dpms+0x88/0x90() - evildoer found and neutralized
Message-ID: <20150930173619.GA3826@pd.tnic>
References: <20150923085950.GA3440@pd.tnic>
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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.

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