ioat2: catch and recover from broken vtd configurations v6

On some platforms (MacPro3,1) the BIOS assigns the ioatdma device to the
incorrect iommu causing faults when the driver initializes. Add a quirk
to catch this misconfiguration and try falling back to untranslated
operation (which works in the MacPro3,1 case).

Assuming there are other platforms with misconfigured iommus teach the
ioatdma driver to treat initialization failures as non-fatal (just fail
the driver load and emit a warning instead of triggering a BUG_ON).

This can be classified as a boot regression since 2.6.32 on affected
platforms since the ioatdma module did not autoload prior to that
kernel.

Cc: <[e-mail]>
Acked-by: David Woodhouse <[e-mail]>
Reported-by: Chris Li <[e-mail]>
Tested-by: Chris Li <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>

drivers/dma/ioat/dma.h

···
 	#define IOAT_RESET_PENDING 2
 	#define IOAT_KOBJ_INIT_FAIL 3
 	#define IOAT_RESHAPE_PENDING 4
+	#define IOAT_RUN 5
 	struct timer_list timer;
 	#define COMPLETION_TIMEOUT msecs_to_jiffies(100)
 	#define IDLE_TIMEOUT msecs_to_jiffies(2000)

drivers/dma/ioat/dma_v2.c

···
 			chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
 			dev_err(to_dev(chan), "%s: Channel halted (%x)\n",
 				__func__, chanerr);
-			BUG_ON(is_ioat_bug(chanerr));
+			if (test_bit(IOAT_RUN, &chan->state))
+				BUG_ON(is_ioat_bug(chanerr));
+			else /* we never got off the ground */
+				return;
 		}
 
 		/* if we haven't made progress and we have already
···
 	return ring;
 }
 
+void ioat2_free_chan_resources(struct dma_chan *c);
+
 /* ioat2_alloc_chan_resources - allocate/initialize ioat2 descriptor ring
  * @chan: channel to be initialized
  */
···
 	struct ioat2_dma_chan *ioat = to_ioat2_chan(c);
 	struct ioat_chan_common *chan = &ioat->base;
 	struct ioat_ring_ent **ring;
+	u64 status;
 	int order;
 
 	/* have we already been set up? */
···
 	tasklet_enable(&chan->cleanup_task);
 	ioat2_start_null_desc(ioat);
 
-	return 1 << ioat->alloc_order;
+	/* check that we got off the ground */
+	udelay(5);
+	status = ioat_chansts(chan);
+	if (is_ioat_active(status) || is_ioat_idle(status)) {
+		set_bit(IOAT_RUN, &chan->state);
+		return 1 << ioat->alloc_order;
+	} else {
+		u32 chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
+
+		dev_WARN(to_dev(chan),
+			"failed to start channel chanerr: %#x\n", chanerr);
+		ioat2_free_chan_resources(c);
+		return -EFAULT;
+	}
 }
 
 bool reshape_ring(struct ioat2_dma_chan *ioat, int order)
···
 	del_timer_sync(&chan->timer);
 	device->cleanup_fn((unsigned long) c);
 	device->reset_hw(chan);
+	clear_bit(IOAT_RUN, &chan->state);
 
 	spin_lock_bh(&chan->cleanup_lock);
 	spin_lock_bh(&ioat->prep_lock);

drivers/dma/ioat/dma_v3.c

···
 			chanerr = readl(chan->reg_base + IOAT_CHANERR_OFFSET);
 			dev_err(to_dev(chan), "%s: Channel halted (%x)\n",
 				__func__, chanerr);
-			BUG_ON(is_ioat_bug(chanerr));
+			if (test_bit(IOAT_RUN, &chan->state))
+				BUG_ON(is_ioat_bug(chanerr));
+			else /* we never got off the ground */
+				return;
 		}
 
 		/* if we haven't made progress and we have already

drivers/pci/intel-iommu.c

···
 
 }
 
+static void quirk_ioat_snb_local_iommu(struct pci_dev *pdev)
+{
+	struct dmar_drhd_unit *drhd;
+	u32 vtbar;
+	int rc;
+
+	/* We know that this device on this chipset has its own IOMMU.
+	 * If we find it under a different IOMMU, then the BIOS is lying
+	 * to us. Hope that the IOMMU for this device is actually
+	 * disabled, and it needs no translation...
+	 */
+	rc = pci_bus_read_config_dword(pdev->bus, PCI_DEVFN(0, 0), 0xb0, &vtbar);
+	if (rc) {
+		/* "can't" happen */
+		dev_info(&pdev->dev, "failed to run vt-d quirk\n");
+		return;
+	}
+	vtbar &= 0xffff0000;
+
+	/* we know that the this iommu should be at offset 0xa000 from vtbar */
+	drhd = dmar_find_matched_drhd_unit(pdev);
+	if (WARN_TAINT_ONCE(!drhd || drhd->reg_base_addr - vtbar != 0xa000,
+			    TAINT_FIRMWARE_WORKAROUND,
+			    "BIOS assigned incorrect VT-d unit for Intel(R) QuickData Technology device\n"))
+		pdev->dev.archdata.iommu = DUMMY_DEVICE_DOMAIN_INFO;
+}
+DECLARE_PCI_FIXUP_ENABLE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_IOAT_SNB, quirk_ioat_snb_local_iommu);
+
 static void __init init_no_remapping_devices(void)
 {
 	struct dmar_drhd_unit *drhd;