[Xen-devel] [PATCH for-4.13 v2] xen/arm: domain_build: Don't expose IOMMU specific properties to hwdom

[Oleksandr Tyshchenko <olekstysh@gmail.com>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

We don't passthrough IOMMU device to hwdom even if it is not used by Xen.
Therefore exposing the properties that describe relationship between
master devices and IOMMUs does not make any sense.

According to the:
1. Documentation/devicetree/bindings/iommu/iommu.txt
2. Documentation/devicetree/bindings/pci/pci-iommu.txt

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

---
Changes V1 [1] -> V2:
   - Only skip IOMMU specific properties of the master device if we
     skip the corresponding IOMMU device
   - Use "hwdom" over "Dom0"

[1] https://lists.xenproject.org/archives/html/xen-devel/2019-10/msg00104.html
---
 xen/arch/arm/domain_build.c | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 6d6dd52..a7321b8 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -480,10 +480,26 @@ static int __init write_properties(struct domain *d, struct kernel_info *kinfo,
     const struct dt_property *prop, *status = NULL;
     int res = 0;
     int had_dom0_bootargs = 0;
+    struct dt_device_node *iommu_node;
 
     if ( kinfo->cmdline && kinfo->cmdline[0] )
         bootargs = &kinfo->cmdline[0];
 
+    /*
+     * If we skip the IOMMU device when creating DT for hwdom (even if
+     * the IOMMU device is not used by Xen), we should also skip the IOMMU
+     * specific properties of the master device behind it in order to avoid
+     * exposing an half complete IOMMU bindings to hwdom.
+     * Use "iommu_node" as an indicator of the master device which properties
+     * should be skipped.
+     */
+    iommu_node = dt_parse_phandle(node, "iommus", 0);
+    if ( iommu_node )
+    {
+        if ( device_get_class(iommu_node) != DEVICE_IOMMU )
+            iommu_node = NULL;
+    }
+
     dt_for_each_property_node (node, prop)
     {
         const void *prop_data = prop->value;
@@ -540,6 +556,19 @@ static int __init write_properties(struct domain *d, struct kernel_info *kinfo,
             continue;
         }
 
+        if ( iommu_node )
+        {
+            /* Don't expose IOMMU specific properties to hwdom */
+            if ( dt_property_name_is_equal(prop, "iommus") )
+                continue;
+
+            if ( dt_property_name_is_equal(prop, "iommu-map") )
+                continue;
+
+            if ( dt_property_name_is_equal(prop, "iommu-map-mask") )
+                continue;
+        }
+
         res = fdt_property(kinfo->fdt, prop->name, prop_data, prop_len);
 
         if ( res )
-- 
2.7.4


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