[Xen-devel] [PATCH v4 21/21] xen/arm: Add the property "protected-devices" in the hypervisor node

[Julien Grall <julien.grall@xxxxxxxxxx>]

DOM0 is using the swiotlb to bounce DMA. When the device is protected by
an IOMMU, we can safely bypass the swiotlb.

We can't disable the swiotlb for all devices because some of them may not
be protected. Only Xen is able to know if an IOMMU protects the device
The new property "protected-devices" is a list of device phandles protected
by an IOMMU.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>

---
    This patch *MUST NOT* be applied until we agreed on a device binding
    the device tree folks.

    Changes in v4:
        - Explained why dt_devlocks is not needed
        - Renamed _cells into cells_iter
        - next_assigned was renamed into domain_list
        - Update commit message to reflect the usage of this property

    Changes in v2:
        - Patch added
---
 xen/arch/arm/domain_build.c |   52 ++++++++++++++++++++++++++++++++++++++-----
 xen/arch/arm/kernel.h       |    3 +++
 2 files changed, 49 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index b9b2fa0..76801f3 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -320,19 +320,22 @@ static int make_memory_node(const struct domain *d,
     return res;
 }
 
-static int make_hypervisor_node(struct domain *d,
-                                void *fdt, const struct dt_device_node *parent)
+static int make_hypervisor_node(struct domain *d, struct kernel_info *kinfo,
+                                const struct dt_device_node *parent)
 {
     const char compat[] =
         "xen,xen-"__stringify(XEN_VERSION)"."__stringify(XEN_SUBVERSION)"\0"
         "xen,xen";
     __be32 reg[4];
     gic_interrupt_t intr;
-    __be32 *cells;
+    __be32 *cells, *cells_iter;
     int res;
     int addrcells = dt_n_addr_cells(parent);
     int sizecells = dt_n_size_cells(parent);
     paddr_t gnttab_start, gnttab_size;
+    const struct dt_device_node *dev;
+    struct hvm_iommu *hd = domain_hvm_iommu(d);
+    void *fdt = kinfo->fdt;
 
     DPRINT("Create hypervisor node\n");
 
@@ -380,6 +383,40 @@ static int make_hypervisor_node(struct domain *d,
     if ( res )
         return res;
 
+    if ( kinfo->num_dev_protected )
+    {
+        /* Don't need to take dtdevs_lock here, because DOM0 building is
+         * done with only 1 CPU online */
+        cells = xmalloc_array(__be32, kinfo->num_dev_protected *
+                              dt_size_to_cells(sizeof(dt_phandle)));
+        if ( !cells )
+            return -FDT_ERR_XEN(ENOMEM);
+
+        cells_iter = cells;
+
+        DPRINT("  List of protected devices\n");
+        list_for_each_entry( dev, &hd->dt_devices, domain_list )
+        {
+            DPRINT("    - %s\n", dt_node_full_name(dev));
+            if ( !dev->phandle )
+            {
+                printk(XENLOG_ERR "Unable to handle protected device (%s)"
+                       "with no phandle", dt_node_full_name(dev));
+                xfree(cells);
+                return -FDT_ERR_XEN(EINVAL);
+            }
+            dt_set_cell(&cells_iter, dt_size_to_cells(sizeof(dt_phandle)),
+                        dev->phandle);
+        }
+
+        res = fdt_property(fdt, "protected-devices", cells,
+                           sizeof (dt_phandle) * kinfo->num_dev_protected);
+
+        xfree(cells);
+        if ( res )
+            return res;
+    }
+
     res = fdt_end_node(fdt);
 
     return res;
@@ -680,7 +717,8 @@ static int make_timer_node(const struct domain *d, void 
*fdt,
 }
 
 /* Map the device in the domain */
-static int map_device(struct domain *d, struct dt_device_node *dev)
+static int map_device(struct domain *d, struct kernel_info *kinfo,
+                      struct dt_device_node *dev)
 {
     unsigned int nirq;
     unsigned int naddr;
@@ -705,6 +743,7 @@ static int map_device(struct domain *d, struct 
dt_device_node *dev)
                    dt_node_full_name(dev));
             return res;
         }
+        kinfo->num_dev_protected++;
     }
 
     /* Map IRQs */
@@ -854,7 +893,7 @@ static int handle_node(struct domain *d, struct kernel_info 
*kinfo,
     if ( !dt_device_type_is_equal(node, "memory") &&
          dt_device_is_available(node) )
     {
-        res = map_device(d, node);
+        res = map_device(d, kinfo, node);
 
         if ( res )
             return res;
@@ -885,7 +924,7 @@ static int handle_node(struct domain *d, struct kernel_info 
*kinfo,
 
     if ( node == dt_host )
     {
-        res = make_hypervisor_node(d, kinfo->fdt, node);
+        res = make_hypervisor_node(d, kinfo, node);
         if ( res )
             return res;
 
@@ -1040,6 +1079,7 @@ int construct_dom0(struct domain *d)
 
     d->max_pages = ~0U;
 
+    kinfo.num_dev_protected = 0;
     kinfo.unassigned_mem = dom0_mem;
 
     rc = kernel_probe(&kinfo);
diff --git a/xen/arch/arm/kernel.h b/xen/arch/arm/kernel.h
index fd2f61d..7acfe3c 100644
--- a/xen/arch/arm/kernel.h
+++ b/xen/arch/arm/kernel.h
@@ -18,6 +18,9 @@ struct kernel_info {
     paddr_t unassigned_mem; /* RAM not (yet) assigned to a bank */
     struct dt_mem_info mem;
 
+    /* Number of devices protected by an IOMMU */
+    unsigned int num_dev_protected;
+
     /* kernel entry point */
     paddr_t entry;
 
-- 
1.7.10.4


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