src/patches/suse-2.6.27.31/patches.arch/x2APIC_PATCH_18_of_41_1cb11583a6c4ceda7426eb36f7bf0419da8dfbc2

   1 From: Suresh Siddha <suresh.b.siddha@intel.com>
   2 Subject: x64, x2apic/intr-remap: disable DMA-remapping if Interrupt-remapping is detected (temporary quirk)
   3 References: fate #303948 and fate #303984
   4 Patch-Mainline: queued for .28
   5 Commit-ID: 1cb11583a6c4ceda7426eb36f7bf0419da8dfbc2
   6
   7 Signed-off-by: Thomas Renninger <trenn@suse.de>
   8
   9 Interrupt-remapping enables queued invalidation. And once queued invalidation
  10 is enabled, IOTLB invalidation also needs to use the queued invalidation
  11 mechanism and the register based IOTLB invalidation doesn't work.
  12
  13 For now, Support for IOTLB invalidation using queued invalidation is
  14 missing. Meanwhile, disable DMA-remapping, if Interrupt-remapping
  15 support is detected.
  16
  17 For the meanwhile, if someone wants to really enable DMA-remapping, they
  18 can use nox2apic, which will disable interrupt-remapping and as such
  19 doesn't enable queued invalidation.
  20
  21 And given that none of the release platforms support intr-remapping yet,
  22 we should be ok for this temporary hack.
  23
  24 Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
  25 Cc: akpm@linux-foundation.org
  26 Cc: arjan@linux.intel.com
  27 Cc: andi@firstfloor.org
  28 Cc: ebiederm@xmission.com
  29 Cc: jbarnes@virtuousgeek.org
  30 Cc: steiner@sgi.com
  31 Signed-off-by: Ingo Molnar <mingo@elte.hu>
  32
  33 ---
  34  drivers/pci/dmar.c |   25 +++++++++++++++++++++++++
  35  1 file changed, 25 insertions(+)
  36
  37 Index: linux-2.6.26/drivers/pci/dmar.c
  38 ===================================================================
  39 --- linux-2.6.26.orig/drivers/pci/dmar.c
  40 +++ linux-2.6.26/drivers/pci/dmar.c
  41 @@ -459,6 +459,31 @@ void __init detect_intel_iommu(void)
  42
  43  #ifdef CONFIG_DMAR
  44         {
  45 +               struct acpi_table_dmar *dmar;
  46 +               /*
  47 +                * for now we will disable dma-remapping when interrupt
  48 +                * remapping is enabled.
  49 +                * When support for queued invalidation for IOTLB invalidation
  50 +                * is added, we will not need this any more.
  51 +                */
  52 +               dmar = (struct acpi_table_dmar *) dmar_tbl;
  53 +               if (ret && cpu_has_x2apic && dmar->flags & 0x1) {
  54 +                       printk(KERN_INFO
  55 +                              "Queued invalidation will be enabled to support "
  56 +                              "x2apic and Intr-remapping.\n");
  57 +                       printk(KERN_INFO
  58 +                              "Disabling IOMMU detection, because of missing "
  59 +                              "queued invalidation support for IOTLB "
  60 +                              "invalidation\n");
  61 +                       printk(KERN_INFO
  62 +                              "Use \"nox2apic\", if you want to use Intel "
  63 +                              " IOMMU for DMA-remapping and don't care about "
  64 +                              " x2apic support\n");
  65 +
  66 +                       dmar_disabled = 1;
  67 +                       return;
  68 +               }
  69 +
  70                 if (ret && !no_iommu && !iommu_detected && !swiotlb &&
  71                     !dmar_disabled)
  72                         iommu_detected = 1;