On 2021-06-17 08:36, Lu Baolu wrote:

On 6/16/21 7:03 PM, John Garry wrote:

quoted

We only ever now set strict mode enabled in iommu_set_dma_strict(), so
just remove the argument.

Signed-off-by: John Garry <redacted>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
---
  drivers/iommu/amd/init.c    | 2 +-
  drivers/iommu/intel/iommu.c | 6 +++---
  drivers/iommu/iommu.c       | 5 ++---
  include/linux/iommu.h       | 2 +-
  4 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index fb3618af643b..7bc460052678 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c

@@ -3099,7 +3099,7 @@ static int __init parse_amd_iommu_options(char 

*str)
      for (; *str; ++str) {
          if (strncmp(str, "fullflush", 9) == 0) {
              pr_warn("amd_iommu=fullflush deprecated; use 
iommu.strict instead\n");
-            iommu_set_dma_strict(true);
+            iommu_set_dma_strict();
          }
          if (strncmp(str, "force_enable", 12) == 0)
              amd_iommu_force_enable = true;

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index d586990fa751..0618c35cfb51 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c

@@ -454,7 +454,7 @@ static int __init intel_iommu_setup(char *str)

              iommu_dma_forcedac = true;
          } else if (!strncmp(str, "strict", 6)) {
              pr_warn("intel_iommu=strict deprecated; use iommu.strict 
instead\n");
-            iommu_set_dma_strict(true);
+            iommu_set_dma_strict();
          } else if (!strncmp(str, "sp_off", 6)) {
              pr_info("Disable supported super page\n");
              intel_iommu_superpage = 0;

@@ -4382,7 +4382,7 @@ int __init intel_iommu_init(void)

           */
          if (cap_caching_mode(iommu->cap)) {
              pr_warn("IOMMU batching disallowed due to 
virtualization\n");
-            iommu_set_dma_strict(true);
+            iommu_set_dma_strict();
          }
          iommu_device_sysfs_add(&iommu->iommu, NULL,
                         intel_iommu_groups,

@@ -5699,7 +5699,7 @@ static void quirk_calpella_no_shadow_gtt(struct 

pci_dev *dev)
      } else if (dmar_map_gfx) {
          /* we have to ensure the gfx device is idle before we flush */
          pci_info(dev, "Disabling batched IOTLB flush on Ironlake\n");
-        iommu_set_dma_strict(true);
+        iommu_set_dma_strict();
      }
  }
  DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x0040, 
quirk_calpella_no_shadow_gtt);

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 60b1ec42e73b..ff221d3ddcbc 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c

@@ -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);

Note that this is the bit that does the real work - if the argument 
parses OK then iommu_dma_strict is reassigned with the appropriate 
value. The iommu_cmd_line stuff is a bit of additional bookkeeping, 
basically just so we can see whether default values have been overridden.

Robin.

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

Best regards,
baolu

quoted

  }
  bool iommu_get_dma_strict(struct iommu_domain *domain)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 32d448050bf7..754f67d6dd90 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h

@@ -476,7 +476,7 @@ int iommu_enable_nesting(struct iommu_domain 

*domain);
  int iommu_set_pgtable_quirks(struct iommu_domain *domain,
          unsigned long quirks);
-void iommu_set_dma_strict(bool val);
+void iommu_set_dma_strict(void);
  bool iommu_get_dma_strict(struct iommu_domain *domain);
  extern int report_iommu_fault(struct iommu_domain *domain, struct 
device *dev,