xen/arm: Xen detection and shared_info page mapping

Check for a node in the device tree compatible with "xen,xen", if it is
present set xen_domain_type to XEN_HVM_DOMAIN and continue
initialization.

Map the real shared info page using XENMEM_add_to_physmap with
XENMAPSPACE_shared_info.

Changes in v4:

- simpler parsing of Xen version in the compatible DT node.

Changes in v3:

- use the "xen,xen" notation rather than "arm,xen";
- add an additional check on the presence of the Xen version.

Changes in v2:

- replace pr_info with pr_debug.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

1 files changed, 61 insertions, 0 deletions

diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index c53554032a60..6a0217d4e662 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -5,6 +5,9 @@
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 #include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
 
 struct start_info _xen_start_info;
 struct start_info *xen_start_info = &_xen_start_info;
@@ -33,3 +36,61 @@ int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
         return -ENOSYS;
 }
 EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
+
+/*
+ * see Documentation/devicetree/bindings/arm/xen.txt for the
+ * documentation of the Xen Device Tree format.
+ */
+static int __init xen_guest_init(void)
+{
+        struct xen_add_to_physmap xatp;
+        static struct shared_info *shared_info_page = 0;
+        struct device_node *node;
+        int len;
+        const char *s = NULL;
+        const char *version = NULL;
+        const char *xen_prefix = "xen,xen-";
+
+        node = of_find_compatible_node(NULL, NULL, "xen,xen");
+        if (!node) {
+                pr_debug("No Xen support\n");
+                return 0;
+        }
+        s = of_get_property(node, "compatible", &len);
+        if (strlen(xen_prefix) + 3  < len &&
+                        !strncmp(xen_prefix, s, strlen(xen_prefix)))
+                version = s + strlen(xen_prefix);
+        if (version == NULL) {
+                pr_debug("Xen version not found\n");
+                return 0;
+        }
+        xen_domain_type = XEN_HVM_DOMAIN;
+
+        if (!shared_info_page)
+                shared_info_page = (struct shared_info *)
+                        get_zeroed_page(GFP_KERNEL);
+        if (!shared_info_page) {
+                pr_err("not enough memory\n");
+                return -ENOMEM;
+        }
+        xatp.domid = DOMID_SELF;
+        xatp.idx = 0;
+        xatp.space = XENMAPSPACE_shared_info;
+        xatp.gpfn = __pa(shared_info_page) >> PAGE_SHIFT;
+        if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp))
+                BUG();
+
+        HYPERVISOR_shared_info = (struct shared_info *)shared_info_page;
+
+        /* xen_vcpu is a pointer to the vcpu_info struct in the shared_info
+         * page, we use it in the event channel upcall and in some pvclock
+         * related functions. We don't need the vcpu_info placement
+         * optimizations because we don't use any pv_mmu or pv_irq op on
+         * HVM.
+         * The shared info contains exactly 1 CPU (the boot CPU). The guest
+         * is required to use VCPUOP_register_vcpu_info to place vcpu info
+         * for secondary CPUs as they are brought up. */
+        per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
+        return 0;
+}
+core_initcall(xen_guest_init);