iommu/vt-d: Make sure IOMMUs are off when intel_iommu=off

When booting into a kexec kernel with intel_iommu=off, and
the previous kernel had intel_iommu=on, the IOMMU hardware
is still enabled and gets not disabled by the new kernel.

This causes the boot to fail because DMA is blocked by the
hardware. Disable the IOMMUs when we find it enabled in the
kexec kernel and boot with intel_iommu=off.
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -4730,6 +4730,15 @@ static int intel_iommu_cpu_dead(unsigned int cpu)
 	return 0;
 }
 
+static void intel_disable_iommus(void)
+{
+	struct intel_iommu *iommu = NULL;
+	struct dmar_drhd_unit *drhd;
+
+	for_each_iommu(iommu, drhd)
+		iommu_disable_translation(iommu);
+}
+
 static inline struct intel_iommu *dev_to_intel_iommu(struct device *dev)
 {
 	return container_of(dev, struct intel_iommu, iommu.dev);
@@ -4840,8 +4849,15 @@ int __init intel_iommu_init(void)
 		goto out_free_dmar;
 	}
 
-	if (no_iommu || dmar_disabled)
+	if (no_iommu || dmar_disabled) {
+		/*
+		 * Make sure the IOMMUs are switched off, even when we
+		 * boot into a kexec kernel and the previous kernel left
+		 * them enabled
+		 */
+		intel_disable_iommus();
 		goto out_free_dmar;
+	}
 
 	if (list_empty(&dmar_rmrr_units))
 		pr_info("No RMRR found\n");