From: Suresh Siddha Subject: x64, x2apic/intr-remap: disable DMA-remapping if Interrupt-remapping is detected (temporary quirk) References: fate #303948 and fate #303984 Patch-Mainline: queued for .28 Commit-ID: 1cb11583a6c4ceda7426eb36f7bf0419da8dfbc2 Signed-off-by: Thomas Renninger Interrupt-remapping enables queued invalidation. And once queued invalidation is enabled, IOTLB invalidation also needs to use the queued invalidation mechanism and the register based IOTLB invalidation doesn't work. For now, Support for IOTLB invalidation using queued invalidation is missing. Meanwhile, disable DMA-remapping, if Interrupt-remapping support is detected. For the meanwhile, if someone wants to really enable DMA-remapping, they can use nox2apic, which will disable interrupt-remapping and as such doesn't enable queued invalidation. And given that none of the release platforms support intr-remapping yet, we should be ok for this temporary hack. Signed-off-by: Suresh Siddha Cc: akpm@linux-foundation.org Cc: arjan@linux.intel.com Cc: andi@firstfloor.org Cc: ebiederm@xmission.com Cc: jbarnes@virtuousgeek.org Cc: steiner@sgi.com Signed-off-by: Ingo Molnar --- drivers/pci/dmar.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) Index: linux-2.6.26/drivers/pci/dmar.c =================================================================== --- linux-2.6.26.orig/drivers/pci/dmar.c +++ linux-2.6.26/drivers/pci/dmar.c @@ -459,6 +459,31 @@ void __init detect_intel_iommu(void) #ifdef CONFIG_DMAR { + struct acpi_table_dmar *dmar; + /* + * for now we will disable dma-remapping when interrupt + * remapping is enabled. + * When support for queued invalidation for IOTLB invalidation + * is added, we will not need this any more. + */ + dmar = (struct acpi_table_dmar *) dmar_tbl; + if (ret && cpu_has_x2apic && dmar->flags & 0x1) { + printk(KERN_INFO + "Queued invalidation will be enabled to support " + "x2apic and Intr-remapping.\n"); + printk(KERN_INFO + "Disabling IOMMU detection, because of missing " + "queued invalidation support for IOTLB " + "invalidation\n"); + printk(KERN_INFO + "Use \"nox2apic\", if you want to use Intel " + " IOMMU for DMA-remapping and don't care about " + " x2apic support\n"); + + dmar_disabled = 1; + return; + } + if (ret && !no_iommu && !iommu_detected && !swiotlb && !dmar_disabled) iommu_detected = 1;