On 2022/2/8 16:05, John Garry wrote:

On 24/01/2022 13:11, Yicong Yang wrote:

quoted

The DMA of HiSilicon PTT device can only work with identical
mapping. So add a quirk for the device to force the domain
passthrough.

This patch should be earlier in the series, before the PTT driver, and the comment on hisi_ptt_check_iommu_mapping() should mention what is going on here.

ok I'll reorder the serives and modify the comments of hisi_ptt_check_iommu_mapping() like:

/*
 * The DMA of PTT trace can only use direct mapping, due to some
 * hardware restriction. Check whether there is an iommu or the
 * policy of the iommu domain is passthrough, otherwise the trace
 * cannot work.
 *
 * The PTT device is supposed to behind the arm smmu v3, which
 * should have passthrough the device by a quirk. Otherwise user
 * should manually set the iommu domain type to identity through
 * sysfs.
 */

quoted

Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
---
  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++++
  1 file changed, 16 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 6dc6d8b6b368..6f67a2b1dd27 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -2838,6 +2838,21 @@ static int arm_smmu_dev_disable_feature(struct device *dev,

      }
  }
  +#define IS_HISI_PTT_DEVICE(pdev)    ((pdev)->vendor == PCI_VENDOR_ID_HUAWEI && \
+                     (pdev)->device == 0xa12e)

I assume that not all revisions will require this check, right?

For current revisions it's necessary.

quoted

+
+static int arm_smmu_def_domain_type(struct device *dev)
+{
+    if (dev_is_pci(dev)) {
+        struct pci_dev *pdev = to_pci_dev(dev);
+
+        if (IS_HISI_PTT_DEVICE(pdev))
+            return IOMMU_DOMAIN_IDENTITY;
+    }
+
+    return 0;
+}
+
  static struct iommu_ops arm_smmu_ops = {
      .capable        = arm_smmu_capable,
      .domain_alloc        = arm_smmu_domain_alloc,

@@ -2863,6 +2878,7 @@ static struct iommu_ops arm_smmu_ops = {

      .sva_unbind        = arm_smmu_sva_unbind,
      .sva_get_pasid        = arm_smmu_sva_get_pasid,
      .page_response        = arm_smmu_page_response,
+    .def_domain_type    = arm_smmu_def_domain_type,
      .pgsize_bitmap        = -1UL, /* Restricted during device attach */
      .owner            = THIS_MODULE,
  };

.

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