[Xen-devel] [PATCH for-4.13 v3] xen/arm: domain_build: Don't expose IOMMU specific properties to hwdom

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

We always skip the IOMMU device when creating DT for hwdom if there is
an appropriate driver for it in Xen (device_get_class(iommu_node)
returns DEVICE_IOMMU). So, even if it is not used by Xen it will be skipped.

We should also skip the IOMMU specific properties of the master device
behind that IOMMU in order to avoid exposing an half complete IOMMU
bindings to hwdom.

According to the Linux's docs:
1. Documentation/devicetree/bindings/iommu/iommu.txt
2. Documentation/devicetree/bindings/pci/pci-iommu.txt

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

---
Changes V2 [2] -> V3:
   - Gather two conditions in one "if"
   - Clarify patch subject/comment in code

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
[2] https://lists.xenproject.org/archives/html/xen-devel/2019-10/msg00673.html
---
 xen/arch/arm/domain_build.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 1d5eac9..6e85ef4 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -480,10 +480,25 @@ 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];
 
+    /*
+     * We always skip the IOMMU device when creating DT for hwdom if there is
+     * an appropriate driver for it in Xen (device_get_class(iommu_node)
+     * returns DEVICE_IOMMU).
+     * We should also skip the IOMMU specific properties of the master device
+     * behind that IOMMU 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 && 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 +555,19 @@ 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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