iommu/vt-d: Detect pre enabled translation

Add code to detect whether translation is already enabled in
the IOMMU. Save this state in a flags field added to
struct intel_iommu.
Tested-by: ZhenHua Li <zhen-hual@hp.com>
Tested-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -443,6 +443,20 @@ static LIST_HEAD(device_domain_list);
 
 static const struct iommu_ops intel_iommu_ops;
 
+static bool translation_pre_enabled(struct intel_iommu *iommu)
+{
+	return (iommu->flags & VTD_FLAG_TRANS_PRE_ENABLED);
+}
+
+static void init_translation_status(struct intel_iommu *iommu)
+{
+	u32 gsts;
+
+	gsts = readl(iommu->reg + DMAR_GSTS_REG);
+	if (gsts & DMA_GSTS_TES)
+		iommu->flags |= VTD_FLAG_TRANS_PRE_ENABLED;
+}
+
 /* Convert generic 'struct iommu_domain to private struct dmar_domain */
 static struct dmar_domain *to_dmar_domain(struct iommu_domain *dom)
 {
@@ -2809,6 +2823,11 @@ static int __init init_dmars(void)
 		if (ret)
 			goto free_iommu;
 
+		init_translation_status(iommu);
+
+		if (translation_pre_enabled(iommu))
+			pr_info("Translation already enabled - trying to copy translation structures\n");
+
 		/*
 		 * TBD:
 		 * we could share the same root & context tables

include/linux/intel-iommu.h

@@ -320,6 +320,9 @@ enum {
 	MAX_SR_DMAR_REGS
 };
 
+#define VTD_FLAG_TRANS_PRE_ENABLED	(1 << 0)
+#define VTD_FLAG_IRQ_REMAP_PRE_ENABLED	(1 << 1)
+
 struct intel_iommu {
 	void __iomem	*reg; /* Pointer to hardware regs, virtual addr */
 	u64 		reg_phys; /* physical address of hw register set */
@@ -351,6 +354,7 @@ struct intel_iommu {
 #endif
 	struct device	*iommu_dev; /* IOMMU-sysfs device */
 	int		node;
+	u32		flags;      /* Software defined flags */
 };
 
 static inline void __iommu_flush_cache(