[PATCH] libxl: arm: Allow grant mappings for backends running on Dom0

[Viresh Kumar <viresh.kumar@xxxxxxxxxx>]

Currently, we add grant mapping related device tree properties if the
backend domain is not Dom0. While Dom0 is privileged and can do foreign
mapping for the entire guest memory, it is still okay for Dom0 to access
guest's memory via grant mappings and hence map only what is required.

This commit adds another parameter for virtio devices, with which they
can do forced grant mappings irrespective of the backend domain id.

Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
 docs/man/xl.cfg.5.pod.in         |  4 ++++
 tools/libs/light/libxl_arm.c     | 21 ++++++++++++---------
 tools/libs/light/libxl_types.idl |  1 +
 tools/libs/light/libxl_virtio.c  | 11 +++++++++++
 tools/xl/xl_parse.c              |  2 ++
 5 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/docs/man/xl.cfg.5.pod.in b/docs/man/xl.cfg.5.pod.in
index 10f37990be57..4879f136aab8 100644
--- a/docs/man/xl.cfg.5.pod.in
+++ b/docs/man/xl.cfg.5.pod.in
@@ -1616,6 +1616,10 @@ properties in the Device Tree, the type field must be 
set to "virtio,device".
 Specifies the transport mechanism for the Virtio device, only "mmio" is
 supported for now.
 
+=item B<forced_grant=BOOLEAN>
+
+Allows Xen Grant memory mapping to be done from Dom0.
+
 =back
 
 =item B<tee="STRING">
diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
index 97c80d7ed0fa..ec2f1844e9b3 100644
--- a/tools/libs/light/libxl_arm.c
+++ b/tools/libs/light/libxl_arm.c
@@ -922,7 +922,8 @@ static int make_xen_iommu_node(libxl__gc *gc, void *fdt)
 
 /* The caller is responsible to complete / close the fdt node */
 static int make_virtio_mmio_node_common(libxl__gc *gc, void *fdt, uint64_t 
base,
-                                        uint32_t irq, uint32_t backend_domid)
+                                        uint32_t irq, uint32_t backend_domid,
+                                        bool forced_grant)
 {
     int res;
     gic_interrupt intr;
@@ -945,7 +946,7 @@ static int make_virtio_mmio_node_common(libxl__gc *gc, void 
*fdt, uint64_t base,
     res = fdt_property(fdt, "dma-coherent", NULL, 0);
     if (res) return res;
 
-    if (backend_domid != LIBXL_TOOLSTACK_DOMID) {
+    if (forced_grant || backend_domid != LIBXL_TOOLSTACK_DOMID) {
         uint32_t iommus_prop[2];
 
         iommus_prop[0] = cpu_to_fdt32(GUEST_PHANDLE_IOMMU);
@@ -959,11 +960,12 @@ static int make_virtio_mmio_node_common(libxl__gc *gc, 
void *fdt, uint64_t base,
 }
 
 static int make_virtio_mmio_node(libxl__gc *gc, void *fdt, uint64_t base,
-                                 uint32_t irq, uint32_t backend_domid)
+                                 uint32_t irq, uint32_t backend_domid,
+                                 bool forced_grant)
 {
     int res;
 
-    res = make_virtio_mmio_node_common(gc, fdt, base, irq, backend_domid);
+    res = make_virtio_mmio_node_common(gc, fdt, base, irq, backend_domid, 
forced_grant);
     if (res) return res;
 
     return fdt_end_node(fdt);
@@ -1019,11 +1021,11 @@ static int make_virtio_mmio_node_gpio(libxl__gc *gc, 
void *fdt)
 
 static int make_virtio_mmio_node_device(libxl__gc *gc, void *fdt, uint64_t 
base,
                                         uint32_t irq, const char *type,
-                                        uint32_t backend_domid)
+                                        uint32_t backend_domid, bool 
forced_grant)
 {
     int res;
 
-    res = make_virtio_mmio_node_common(gc, fdt, base, irq, backend_domid);
+    res = make_virtio_mmio_node_common(gc, fdt, base, irq, backend_domid, 
forced_grant);
     if (res) return res;
 
     /* Add device specific nodes */
@@ -1363,7 +1365,7 @@ static int libxl__prepare_dtb(libxl__gc *gc, 
libxl_domain_config *d_config,
                     iommu_needed = true;
 
                 FDT( make_virtio_mmio_node(gc, fdt, disk->base, disk->irq,
-                                           disk->backend_domid) );
+                                           disk->backend_domid, false) );
             }
         }
 
@@ -1373,12 +1375,13 @@ static int libxl__prepare_dtb(libxl__gc *gc, 
libxl_domain_config *d_config,
             if (virtio->transport != LIBXL_VIRTIO_TRANSPORT_MMIO)
                 continue;
 
-            if (virtio->backend_domid != LIBXL_TOOLSTACK_DOMID)
+            if (virtio->forced_grant || virtio->backend_domid != 
LIBXL_TOOLSTACK_DOMID)
                 iommu_needed = true;
 
             FDT( make_virtio_mmio_node_device(gc, fdt, virtio->base,
                                               virtio->irq, virtio->type,
-                                              virtio->backend_domid) );
+                                              virtio->backend_domid,
+                                              virtio->forced_grant) );
         }
 
         /*
diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
index c10292e0d7e3..cfbcd717dc7f 100644
--- a/tools/libs/light/libxl_types.idl
+++ b/tools/libs/light/libxl_types.idl
@@ -740,6 +740,7 @@ libxl_device_virtio = Struct("device_virtio", [
     ("backend_domname", string),
     ("type", string),
     ("transport", libxl_virtio_transport),
+    ("forced_grant", bool),
     ("devid", libxl_devid),
     # Note that virtio-mmio parameters (irq and base) are for internal
     # use by libxl and can't be modified.
diff --git a/tools/libs/light/libxl_virtio.c b/tools/libs/light/libxl_virtio.c
index faada49e184e..e1f15344ef97 100644
--- a/tools/libs/light/libxl_virtio.c
+++ b/tools/libs/light/libxl_virtio.c
@@ -48,11 +48,13 @@ static int libxl__set_xenstore_virtio(libxl__gc *gc, 
uint32_t domid,
     flexarray_append_pair(back, "base", GCSPRINTF("%#"PRIx64, virtio->base));
     flexarray_append_pair(back, "type", GCSPRINTF("%s", virtio->type));
     flexarray_append_pair(back, "transport", GCSPRINTF("%s", transport));
+    flexarray_append_pair(back, "forced_grant", GCSPRINTF("%u", 
virtio->forced_grant));
 
     flexarray_append_pair(front, "irq", GCSPRINTF("%u", virtio->irq));
     flexarray_append_pair(front, "base", GCSPRINTF("%#"PRIx64, virtio->base));
     flexarray_append_pair(front, "type", GCSPRINTF("%s", virtio->type));
     flexarray_append_pair(front, "transport", GCSPRINTF("%s", transport));
+    flexarray_append_pair(front, "forced_grant", GCSPRINTF("%u", 
virtio->forced_grant));
 
     return 0;
 }
@@ -104,6 +106,15 @@ static int libxl__virtio_from_xenstore(libxl__gc *gc, 
const char *libxl_path,
         }
     }
 
+    tmp = NULL;
+    rc = libxl__xs_read_checked(gc, XBT_NULL,
+                               GCSPRINTF("%s/forced_grant", be_path), &tmp);
+    if (rc) goto out;
+
+    if (tmp) {
+        virtio->forced_grant = strtoul(tmp, NULL, 0);
+    }
+
     tmp = NULL;
     rc = libxl__xs_read_checked(gc, XBT_NULL,
                                GCSPRINTF("%s/type", be_path), &tmp);
diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
index 1f6f47daf4e1..3e34da099785 100644
--- a/tools/xl/xl_parse.c
+++ b/tools/xl/xl_parse.c
@@ -1215,6 +1215,8 @@ static int parse_virtio_config(libxl_device_virtio 
*virtio, char *token)
     } else if (MATCH_OPTION("transport", token, oparg)) {
         rc = libxl_virtio_transport_from_string(oparg, &virtio->transport);
         if (rc) return rc;
+    } else if (MATCH_OPTION("forced_grant", token, oparg)) {
+        virtio->forced_grant = strtoul(oparg, NULL, 0);
     } else {
         fprintf(stderr, "Unknown string \"%s\" in virtio spec\n", token);
         return -1;
-- 
2.31.1.272.g89b43f80a514