iommu/vt-d: Disable translation if already enabled

This patch disables translation(dma-remapping) before its initialization
if it is already enabled.

This is needed for kexec/kdump boot. If dma-remapping is enabled in the
first kernel, it need to be disabled before initializing its page table
during second kernel boot. Wei Hu also reported that this is needed
when second kernel boots with intel_iommu=off.

Basically iommu->gcmd is used to know whether translation is enabled or
disabled, but it is always zero at boot time even when translation is
enabled since iommu->gcmd is initialized without considering such a
case. Therefor this patch synchronizes iommu->gcmd value with global
command register when iommu structure is allocated.

Signed-off-by: Takao Indoh <indou.takao@jp.fujitsu.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 0099667a397e..414d2d20dd59 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -3665,6 +3665,7 @@ static struct notifier_block device_nb = {
 int __init intel_iommu_init(void)
 {
         int ret = 0;
+        struct dmar_drhd_unit *drhd;
 
         /* VT-d is required for a TXT/tboot launch, so enforce that */
         force_on = tboot_force_iommu();
@@ -3675,6 +3676,20 @@ int __init intel_iommu_init(void)
                 return  -ENODEV;
         }
 
+        /*
+         * Disable translation if already enabled prior to OS handover.
+         */
+        for_each_drhd_unit(drhd) {
+                struct intel_iommu *iommu;
+
+                if (drhd->ignored)
+                        continue;
+
+                iommu = drhd->iommu;
+                if (iommu->gcmd & DMA_GCMD_TE)
+                        iommu_disable_translation(iommu);
+        }
+
         if (dmar_dev_scope_init() < 0) {
                 if (force_on)
                         panic("tboot: Failed to initialize DMAR device scope\n");