intel-iommu: Yet another BIOS workaround: Isoch DMAR unit with no TLB space

Asus decided to ship a BIOS which configures sound DMA to go via the
dedicated IOMMU unit, but assigns precisely zero TLB entries to that
unit. Which causes the whole thing to deadlock, including the DMA
traffic on the _other_ IOMMU units. Nice one.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/pci/intel-iommu.c

@@ -48,6 +48,7 @@
 
 #define IS_GFX_DEVICE(pdev) ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY)
 #define IS_ISA_DEVICE(pdev) ((pdev->class >> 8) == PCI_CLASS_BRIDGE_ISA)
+#define IS_AZALIA(pdev) ((pdev)->vendor == 0x8086 && (pdev)->device == 0x3a3e)
 
 #define IOAPIC_RANGE_START	(0xfee00000)
 #define IOAPIC_RANGE_END	(0xfeefffff)
@@ -94,6 +95,7 @@ static inline unsigned long virt_to_dma_pfn(void *p)
 /* global iommu list, set NULL for ignored DMAR units */
 static struct intel_iommu **g_iommus;
 
+static void __init check_tylersburg_isoch(void);
 static int rwbf_quirk;
 
 /*
@@ -1934,6 +1936,9 @@ static struct dmar_domain *get_domain_for_dev(struct pci_dev *pdev, int gaw)
 }
 
 static int iommu_identity_mapping;
+#define IDENTMAP_ALL		1
+#define IDENTMAP_GFX		2
+#define IDENTMAP_AZALIA		4
 
 static int iommu_domain_identity_map(struct dmar_domain *domain,
 				     unsigned long long start,
@@ -2151,8 +2156,14 @@ static int domain_add_dev_info(struct dmar_domain *domain,
 
 static int iommu_should_identity_map(struct pci_dev *pdev, int startup)
 {
-	if (iommu_identity_mapping == 2)
-		return IS_GFX_DEVICE(pdev);
+	if ((iommu_identity_mapping & IDENTMAP_AZALIA) && IS_AZALIA(pdev))
+		return 1;
+
+	if ((iommu_identity_mapping & IDENTMAP_GFX) && IS_GFX_DEVICE(pdev))
+		return 1;
+
+	if (!(iommu_identity_mapping & IDENTMAP_ALL))
+		return 0;
 
 	/*
 	 * We want to start off with all devices in the 1:1 domain, and
@@ -2332,11 +2343,14 @@ int __init init_dmars(void)
 	}
 
 	if (iommu_pass_through)
-		iommu_identity_mapping = 1;
+		iommu_identity_mapping |= IDENTMAP_ALL;
+
 #ifdef CONFIG_DMAR_BROKEN_GFX_WA
-	else
-		iommu_identity_mapping = 2;
+	iommu_identity_mapping |= IDENTMAP_GFX;
 #endif
+
+	check_tylersburg_isoch();
+
 	/*
 	 * If pass through is not set or not enabled, setup context entries for
 	 * identity mappings for rmrr, gfx, and isa and may fall back to static
@@ -3670,3 +3684,61 @@ static void __devinit quirk_iommu_rwbf(struct pci_dev *dev)
 }
 
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x2a40, quirk_iommu_rwbf);
+
+/* On Tylersburg chipsets, some BIOSes have been known to enable the
+   ISOCH DMAR unit for the Azalia sound device, but not give it any
+   TLB entries, which causes it to deadlock. Check for that.  We do
+   this in a function called from init_dmars(), instead of in a PCI
+   quirk, because we don't want to print the obnoxious "BIOS broken"
+   message if VT-d is actually disabled.
+*/
+static void __init check_tylersburg_isoch(void)
+{
+	struct pci_dev *pdev;
+	uint32_t vtisochctrl;
+
+	/* If there's no Azalia in the system anyway, forget it. */
+	pdev = pci_get_device(PCI_VENDOR_ID_INTEL, 0x3a3e, NULL);
+	if (!pdev)
+		return;
+	pci_dev_put(pdev);
+
+	/* System Management Registers. Might be hidden, in which case
+	   we can't do the sanity check. But that's OK, because the
+	   known-broken BIOSes _don't_ actually hide it, so far. */
+	pdev = pci_get_device(PCI_VENDOR_ID_INTEL, 0x342e, NULL);
+	if (!pdev)
+		return;
+
+	if (pci_read_config_dword(pdev, 0x188, &vtisochctrl)) {
+		pci_dev_put(pdev);
+		return;
+	}
+
+	pci_dev_put(pdev);
+
+	/* If Azalia DMA is routed to the non-isoch DMAR unit, fine. */
+	if (vtisochctrl & 1)
+		return;
+
+	/* Drop all bits other than the number of TLB entries */
+	vtisochctrl &= 0x1c;
+
+	/* If we have the recommended number of TLB entries (16), fine. */
+	if (vtisochctrl == 0x10)
+		return;
+
+	/* Zero TLB entries? You get to ride the short bus to school. */
+	if (!vtisochctrl) {
+		WARN(1, "Your BIOS is broken; DMA routed to ISOCH DMAR unit but no TLB space.\n"
+		     "BIOS vendor: %s; Ver: %s; Product Version: %s\n",
+		     dmi_get_system_info(DMI_BIOS_VENDOR),
+		     dmi_get_system_info(DMI_BIOS_VERSION),
+		     dmi_get_system_info(DMI_PRODUCT_VERSION));
+		iommu_identity_mapping |= IDENTMAP_AZALIA;
+		return;
+	}
+	
+	printk(KERN_WARNING "DMAR: Recommended TLB entries for ISOCH unit is 16; your BIOS set %d\n",
+	       vtisochctrl);
+}