Enable usage of bootfdt for populating the boot info struct from the
firmware-provided device tree.  Also enable the Xen boot page allocator.

Additionally, modify bootfdt.c's boot_fdt_info() to tolerate the
scenario in which the FDT overlaps a reserved memory region, as is the
case on PPC when booted directly from skiboot. Since this means that Xen
can now boot without a BOOTMOD_FDT present in bootinfo, clarify this
fact in a comment above BOOTMOD_FDT's definition.

Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com>
Acked-by: Julien Grall <jgrall@amazon.com>
---
Changes in v5:
  - Drop setup.c's unnecessary `boot_fdt` variable per Julien's suggestion

 xen/arch/ppc/setup.c             | 20 +++++++++++++++++++-
 xen/common/device-tree/bootfdt.c | 11 +++++++++--
 2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/xen/arch/ppc/setup.c b/xen/arch/ppc/setup.c
index 5fb5ab64e3..17bc1aed34 100644
--- a/xen/arch/ppc/setup.c
+++ b/xen/arch/ppc/setup.c
@@ -1,4 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-or-later */
+#include <xen/bootfdt.h>
+#include <xen/device_tree.h>
 #include <xen/init.h>
 #include <xen/lib.h>
 #include <xen/mm.h>
@@ -9,6 +11,7 @@
 #include <asm/early_printk.h>
 #include <asm/mm.h>
 #include <asm/processor.h>
+#include <asm/setup.h>

 /* Xen stack for bringing up the first CPU. */
 unsigned char __initdata cpu0_boot_stack[STACK_SIZE] __aligned(STACK_SIZE);
@@ -26,6 +29,8 @@ void __init noreturn start_xen(unsigned long r3, unsigned long r4,
                                unsigned long r5, unsigned long r6,
                                unsigned long r7)
 {
+    const struct bootmodule *xen_bootmodule;
+
     if ( r5 )
     {
         /* Unsupported OpenFirmware boot protocol */
@@ -34,11 +39,24 @@ void __init noreturn start_xen(unsigned long r3, unsigned long r4,
     else
     {
         /* kexec boot protocol */
-        boot_opal_init((void *)r3);
+        device_tree_flattened = (void *)r3;
+        boot_opal_init(device_tree_flattened);
     }

     setup_exceptions();

+    boot_fdt_info(device_tree_flattened, r3);
+
+    /*
+     * Xen relocates itself at the ppc64 entrypoint, so we need to manually mark
+     * the kernel module.
+     */
+    xen_bootmodule = add_boot_module(BOOTMOD_XEN, __pa(_start),
+                                     PAGE_ALIGN(__pa(_end)), false);
+    BUG_ON(!xen_bootmodule);
+
+    populate_boot_allocator();
+
     setup_initial_pagetables();

     init_constructors();
diff --git a/xen/common/device-tree/bootfdt.c b/xen/common/device-tree/bootfdt.c
index 2a51ee44a3..5facd683b8 100644
--- a/xen/common/device-tree/bootfdt.c
+++ b/xen/common/device-tree/bootfdt.c
@@ -584,8 +584,6 @@ size_t __init boot_fdt_info(const void *fdt, paddr_t paddr)
     if ( ret < 0 )
         panic("No valid device tree\n");

-    add_boot_module(BOOTMOD_FDT, paddr, fdt_totalsize(fdt), false);
-
     nr_rsvd = fdt_num_mem_rsv(fdt);
     if ( nr_rsvd < 0 )
         panic("Parsing FDT memory reserve map failed (%d)\n", nr_rsvd);
@@ -632,6 +630,15 @@ size_t __init boot_fdt_info(const void *fdt, paddr_t paddr)
             panic("Cannot allocate reserved memory bank\n");
     }

+    /*
+     * Add module for the FDT itself after the device tree has been parsed. This
+     * is required on ppc64le where the device tree passed to Xen may have been
+     * allocated by skiboot, in which case it will exist within a reserved
+     * region and this call will fail. This is fine, however, since either way
+     * the allocator will know not to step on the device tree.
+     */
+    (void)add_boot_module(BOOTMOD_FDT, paddr, fdt_totalsize(fdt), false);
+
     /*
      * On Arm64 setup_directmap_mappings() expects to be called with the lowest
      * bank in memory first. There is no requirement that the DT will provide
--
2.30.2