On 6/17/21 3:41 PM, John Garry wrote:

quoted

quoted

@@ -349,10 +349,9 @@ static int __init iommu_dma_setup(char *str)

  }
  early_param("iommu.strict", iommu_dma_setup);
-void iommu_set_dma_strict(bool strict)
+void iommu_set_dma_strict(void)
  {
-    if (strict || !(iommu_cmd_line & IOMMU_CMD_LINE_STRICT))
-        iommu_dma_strict = strict;
+    iommu_dma_strict = true;

Sorry, I still can't get how iommu.strict kernel option works.

static int __init iommu_dma_setup(char *str)
{
         int ret = kstrtobool(str, &iommu_dma_strict);

         if (!ret)
                 iommu_cmd_line |= IOMMU_CMD_LINE_STRICT;
         return ret;
}
early_param("iommu.strict", iommu_dma_setup);

The bit IOMMU_CMD_LINE_STRICT is only set, but not used anywhere.

It is used in patch 2/6:

+    pr_info("DMA domain TLB invalidation policy: %s mode %s\n",
+        iommu_dma_strict ? "strict" : "lazy",
+        (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
+            "(set via kernel command line)" : "");

quoted

Hence,
I am wondering how could it work? A bug or I missed anything?

It is really just used for informative purpose now.

I am clear now. Thanks!

Best regards,
baolu