2 files changed, 37 insertions, 0 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 5cf941774347..c2d24991bb2b 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -772,6 +772,16 @@ config DMAR_GFX_WA
          all the OS-visible memory. Hence the driver can continue
          to use physical addresses for DMA.
 
+config DMAR_FLOPPY_WA
+        bool
+        depends on DMAR
+        default y
+        help
+         Floppy disk drivers are know to bypass DMA API calls
+         thereby failing to work when IOMMU is enabled. This
+         workaround will setup a 1:1 mapping for the first
+         16M to make floppy (an ISA device) work.
+
 source "drivers/pci/pcie/Kconfig"
 
 source "drivers/pci/Kconfig"
diff --git a/drivers/pci/intel-iommu.c b/drivers/pci/intel-iommu.c
index 4905e0e3a644..4cca5b939e0e 100644
--- a/drivers/pci/intel-iommu.c
+++ b/drivers/pci/intel-iommu.c
@@ -1632,6 +1632,31 @@ error:
 }
 #endif
 
+#ifdef CONFIG_DMAR_FLOPPY_WA
+static inline void iommu_prepare_isa(void)
+{
+        struct pci_dev *pdev;
+        int ret;
+
+        pdev = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL);
+        if (!pdev)
+                return;
+
+        printk(KERN_INFO "IOMMU: Prepare 0-16M unity mapping for LPC\n");
+        ret = iommu_prepare_identity_map(pdev, 0, 16*1024*1024);
+
+        if (ret)
+                printk("IOMMU: Failed to create 0-64M identity map, "
+                        "floppy might not work\n");
+
+}
+#else
+static inline void iommu_prepare_isa(void)
+{
+        return;
+}
+#endif /* !CONFIG_DMAR_FLPY_WA */
+
 int __init init_dmars(void)
 {
         struct dmar_drhd_unit *drhd;
@@ -1697,6 +1722,8 @@ int __init init_dmars(void)
 
         iommu_prepare_gfx_mapping();
 
+        iommu_prepare_isa();
+
         /*
          * for each drhd
          *   enable fault log