iommu/vt-d: Don't copy translation tables if RTT bit needs to be changed

We can't change the RTT bit when translation is enabled, so
don't copy translation tables when we would change the bit
with our new root entry.
Tested-by: NZhenHua Li <zhen-hual@hp.com>
Tested-by: NBaoquan He <bhe@redhat.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -2934,10 +2934,20 @@ static int copy_translation_tables(struct intel_iommu *iommu)
 	unsigned long flags;
 	u64 rtaddr_reg;
 	int bus, ret;
-	bool ext;
+	bool new_ext, ext;
 
 	rtaddr_reg = dmar_readq(iommu->reg + DMAR_RTADDR_REG);
 	ext        = !!(rtaddr_reg & DMA_RTADDR_RTT);
+	new_ext    = !!ecap_ecs(iommu->ecap);
+
+	/*
+	 * The RTT bit can only be changed when translation is disabled,
+	 * but disabling translation means to open a window for data
+	 * corruption. So bail out and don't copy anything if we would
+	 * have to change the bit.
+	 */
+	if (new_ext != ext)
+		return -EINVAL;
 
 	old_rt_phys = rtaddr_reg & VTD_PAGE_MASK;
 	if (!old_rt_phys)