intel-iommu: Workaround IOTLB hang on Ironlake GPU

To work around a hardware issue, we have to submit IOTLB flushes while
the graphics engine is idle. The graphics driver will (we hope) go to
great lengths to ensure that it gets that right on the affected
chipset(s)... so let's not screw it over by deferring the unmap and
doing it later. That wouldn't be very helpful.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index c621c98c99da00886931b3aed1b8364c7de6b958..ff266034ead8aa530c3dcffef977dec9f64dc91e 100644 (file)
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3950,7 +3950,11 @@ static void __devinit quirk_calpella_no_shadow_gtt(struct pci_dev *dev)
        if (!(ggc & GGC_MEMORY_VT_ENABLED)) {
                printk(KERN_INFO "DMAR: BIOS has allocated no shadow GTT; disabling IOMMU for graphics\n");
                dmar_map_gfx = 0;
-       }
+       } else if (dmar_map_gfx) {
+               /* we have to ensure the gfx device is idle before we flush */
+               printk(KERN_INFO "DMAR: Disabling batched IOTLB flush on Ironlake\n");
+               intel_iommu_strict = 1;
+       }
 }
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x0040, quirk_calpella_no_shadow_gtt);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x0044, quirk_calpella_no_shadow_gtt);