[PATCH 03/12] xen/arm: introduce 1:1 mapping for domUs

[Stefano Stabellini <sstabellini@kernel.org>]

In some cases it is desirable to map domU memory 1:1 (guest physical ==
physical.) For instance, because we want to assign a device to the domU
but the IOMMU is not present or cannot be used. In these cases, other
mechanisms should be used for DMA protection, e.g. a MPU.

This patch introduces a new device tree option for dom0less guests to
request a domain to be directly mapped. It also specifies the memory
ranges. This patch documents the new attribute and parses it at boot
time. (However, the implementation of 1:1 mapping is missing and just
BUG() out at the moment.)  Finally the patch sets the new direct_map
flag for DomU domains.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xilinx.com>
---
 docs/misc/arm/device-tree/booting.txt | 13 +++++++
 docs/misc/arm/passthrough-noiommu.txt | 35 ++++++++++++++++++
 xen/arch/arm/domain_build.c           | 52 +++++++++++++++++++++++++--
 3 files changed, 98 insertions(+), 2 deletions(-)
 create mode 100644 docs/misc/arm/passthrough-noiommu.txt

diff --git a/docs/misc/arm/device-tree/booting.txt b/docs/misc/arm/device-tree/booting.txt
index 5243bc7fd3..fce5f7ed5a 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -159,6 +159,19 @@ with the following properties:
     used, or GUEST_VPL011_SPI+1 if vpl011 is enabled, whichever is
     greater.
 
+- direct-map
+
+    Optional. An array of integer pairs specifying addresses and sizes.
+    direct_map requests the memory of the domain to be 1:1 mapped with
+    the memory ranges specified as argument. Only sizes that are a
+    power of two number of pages are allowed.
+
+- #direct-map-addr-cells and #direct-map-size-cells
+
+    The number of cells to use for the addresses and for the sizes in
+    direct-map. Default and maximum are 2 cells for both addresses and
+    sizes.
+
 - #address-cells and #size-cells
 
     Both #address-cells and #size-cells need to be specified because
diff --git a/docs/misc/arm/passthrough-noiommu.txt b/docs/misc/arm/passthrough-noiommu.txt
new file mode 100644
index 0000000000..d2bfaf26c3
--- /dev/null
+++ b/docs/misc/arm/passthrough-noiommu.txt
@@ -0,0 +1,35 @@
+Request Device Assignment without IOMMU support
+===============================================
+
+Add xen,force-assign-without-iommu; to the device tree snippet
+
+    ethernet: ethernet@ff0e0000 {
+        compatible = "cdns,zynqmp-gem";
+        xen,path = "/amba/ethernet@ff0e0000";
+        xen,reg = <0x0 0xff0e0000 0x1000 0x0 0xff0e0000>;
+        xen,force-assign-without-iommu;
+
+Optionally, if none of the domains require an IOMMU, then it could be
+disabled (not recommended). For instance by adding status = "disabled";
+under the smmu node:
+
+    smmu@fd800000 {
+        compatible = "arm,mmu-500";
+        status = "disabled";
+
+
+Request 1:1 memory mapping for the dom0-less domain
+===================================================
+
+Add a direct-map property under the appropriate /chosen/domU node with
+the memory ranges you want to assign to your domain. If you are using
+imagebuilder, you can add to boot.source something like the following:
+
+    fdt set /chosen/domU0 direct-map <0x0 0x10000000 0x0 0x10000000 0x0 0x60000000 0x0 0x10000000>
+
+Which will assign the ranges:
+
+    0x10000000 - 0x20000000
+    0x60000000 - 0x70000000
+
+to the first dom0less domU.
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 2ec7453aa3..a2bb411568 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -2435,7 +2435,51 @@ static int __init construct_domU(struct domain *d,
     /* type must be set before allocate memory */
     d->arch.type = kinfo.type;
 #endif
-    allocate_memory(d, &kinfo);
+
+    if ( !is_domain_direct_mapped(d) )
+        allocate_memory(d, &kinfo);
+    else
+    {
+        struct membank banks[NR_MEM_BANKS];
+        const struct dt_property *prop;
+        u32 direct_map_len, direct_map_addr_len = 2, direct_map_size_len = 2;
+        unsigned int i;
+        __be32 *p;
+
+        prop = dt_find_property(node, "direct-map", &direct_map_len);
+        BUG_ON(!prop);
+
+        dt_property_read_u32(node,
+                             "#direct-map-addr-cells",
+                             &direct_map_addr_len);
+        dt_property_read_u32(node,
+                             "#direct-map-size-cells",
+                             &direct_map_size_len);
+        BUG_ON(direct_map_size_len > 2 || direct_map_addr_len > 2);
+
+        for ( i = 0, p = prop->value;
+              i < direct_map_len /
+                  (4 * (direct_map_addr_len + direct_map_size_len));
+              i++)
+        {
+            int j;
+
+            banks[i].start = 0;
+            for ( j = 0; j < direct_map_addr_len; j++, p++ )
+                banks[i].start |= __be32_to_cpu(*p) << (32*j);
+
+            banks[i].size = 0;
+            for ( j = 0; j < direct_map_size_len; j++, p++ )
+                banks[i].size |= __be32_to_cpu(*p) << (32*j);
+
+            printk(XENLOG_DEBUG
+                   "direct_map start=%#"PRIpaddr" size=%#"PRIpaddr"\n",
+                   banks[i].start, banks[i].size);
+        }
+
+        /* reserve_memory_11(d, &kinfo, &banks[0], i); */
+        BUG();
+    }
 
     rc = prepare_dtb_domU(d, &kinfo);
     if ( rc < 0 )
@@ -2455,6 +2499,7 @@ void __init create_domUs(void)
 {
     struct dt_device_node *node;
     const struct dt_device_node *chosen = dt_find_node_by_path("/chosen");
+    u32 direct_map = 0;
 
     BUG_ON(chosen == NULL);
     dt_for_each_child_node(chosen, node)
@@ -2476,8 +2521,11 @@ void __init create_domUs(void)
             panic("Missing property 'cpus' for domain %s\n",
                   dt_node_name(node));
 
-        if ( dt_find_compatible_node(node, NULL, "multiboot,device-tree") )
+        dt_find_property(node, "direct-map", &direct_map);
+        if ( dt_find_compatible_node(node, NULL, "multiboot,device-tree") &&
+             !direct_map )
             d_cfg.flags |= XEN_DOMCTL_CDF_iommu;
+        flags.arch.is_direct_map = direct_map != 0;
 
         if ( !dt_property_read_u32(node, "nr_spis", &d_cfg.arch.nr_spis) )
         {
-- 
2.17.1