AMD IOMMU: add parameter to disable device isolation

Impact: add a new AMD IOMMU kernel command line parameter

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

2 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9fa6508892c2..b56ee02d2514 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -295,6 +295,8 @@ and is between 256 and 4096 characters. It is defined in the file
                         isolate - enable device isolation (each device, as far
                                   as possible, will get its own protection
                                   domain)
+                        share - put every device behind one IOMMU into the
+                                same protection domain
                         fullflush - enable flushing of IO/TLB entries when
                                     they are unmapped. Otherwise they are
                                     flushed before they will be reused, which
diff --git a/arch/x86/kernel/amd_iommu_init.c b/arch/x86/kernel/amd_iommu_init.c
index 0cdcda35a05f..838a2e1d5bb2 100644
--- a/arch/x86/kernel/amd_iommu_init.c
+++ b/arch/x86/kernel/amd_iommu_init.c
@@ -1213,6 +1213,8 @@ static int __init parse_amd_iommu_options(char *str)
         for (; *str; ++str) {
                 if (strncmp(str, "isolate", 7) == 0)
                         amd_iommu_isolate = 1;
+                if (strncmp(str, "share", 5) == 0)
+                        amd_iommu_isolate = 0;
                 if (strncmp(str, "fullflush", 11) == 0)
                         amd_iommu_unmap_flush = true;
         }