Prior to these IOMMU patches, the passthrough option could not be used because it would cause the kernel to panic. Provide an indication that a kernel is capable of handling passthrough mode through the introduction of a specific variable name. This allows automatic configuration utilities to set the "iommu=pt" kernel cmdline option safely. Signed-off-by: Mike Travis Acked-by: Dimitri Sivanich --- drivers/pci/intel-iommu.c | 4 ++++ 1 file changed, 4 insertions(+) --- linux.orig/drivers/pci/intel-iommu.c +++ linux/drivers/pci/intel-iommu.c @@ -390,6 +390,9 @@ static int dmar_map_gfx = 1; static int dmar_forcedac; static int intel_iommu_strict; +/* specifically named variable that indicates "iommu=pt" is available */ +static int __initdata intel_iommu_64bit_pt; + #define DUMMY_DEVICE_DOMAIN_INFO ((struct device_domain_info *)(-1)) static DEFINE_SPINLOCK(device_domain_lock); static LIST_HEAD(device_domain_list); @@ -425,6 +428,7 @@ static int __init intel_iommu_setup(char while (*str == ',') str++; } + intel_iommu_64bit_pt = 1; return 0; } __setup("intel_iommu=", intel_iommu_setup); --