board: Introduce xenguest_arm64 board

Introduce a minimal Xen guest board running as a virtual
machine under Xen Project's hypervisor [1], [2].

Part of the code is ported from Xen mini-os and also uses
work initially done by different authors from NXP: please see
relevant files for their copyrights.

[1] https://xenbits.xen.org
[2] https://wiki.xenproject.org/

Signed-off-by: Andrii Anisov <andrii_anisov@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>

board/xen/xenguest_arm64/Kconfig

@@ -0,0 +1,12 @@
+if TARGET_XENGUEST_ARM64
+
+config SYS_BOARD
+	default "xenguest_arm64"
+
+config SYS_VENDOR
+	default "xen"
+
+config SYS_CONFIG_NAME
+	default "xenguest_arm64"
+
+endif

board/xen/xenguest_arm64/MAINTAINERS

@@ -0,0 +1,7 @@
+XEN GUEST FOR ARM64
+M:	Andrii Anisov <andrii_anisov@epam.com>
+S:	Maintained
+F:	board/xen/xenguest_arm64/
+F:	doc/board/xen/
+F:	include/configs/xenguest_arm64.h
+F:	configs/xenguest_arm64_defconfig

board/xen/xenguest_arm64/Makefile

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier:	GPL-2.0+
+#
+# (C) Copyright 2020 EPAM Systems Inc.
+
+obj-y	:= xenguest_arm64.o

board/xen/xenguest_arm64/xenguest_arm64.c

@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * (C) 2013
+ * David Feng <fenghua@phytium.com.cn>
+ * Sharma Bhupesh <bhupesh.sharma@freescale.com>
+ *
+ * (C) 2020 EPAM Systems Inc
+ */
+
+#include <common.h>
+#include <cpu_func.h>
+#include <dm.h>
+#include <errno.h>
+#include <malloc.h>
+
+#include <asm/io.h>
+#include <asm/armv8/mmu.h>
+#include <asm/xen.h>
+#include <asm/xen/hypercall.h>
+
+#include <linux/compiler.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+int board_init(void)
+{
+	return 0;
+}
+
+/*
+ * Use fdt provided by Xen: according to
+ * https://www.kernel.org/doc/Documentation/arm64/booting.txt
+ * x0 is the physical address of the device tree blob (dtb) in system RAM.
+ * This is stored in rom_pointer during low level init.
+ */
+void *board_fdt_blob_setup(void)
+{
+	if (fdt_magic(rom_pointer[0]) != FDT_MAGIC)
+		return NULL;
+	return (void *)rom_pointer[0];
+}
+
+#define MAX_MEM_MAP_REGIONS 5
+static struct mm_region xen_mem_map[MAX_MEM_MAP_REGIONS];
+struct mm_region *mem_map = xen_mem_map;
+
+static int get_next_memory_node(const void *blob, int mem)
+{
+	do {
+		mem = fdt_node_offset_by_prop_value(blob, mem,
+						    "device_type", "memory", 7);
+	} while (!fdtdec_get_is_enabled(blob, mem));
+
+	return mem;
+}
+
+static int setup_mem_map(void)
+{
+	int i, ret, mem, reg = 0;
+	struct fdt_resource res;
+	const void *blob = gd->fdt_blob;
+
+	mem = get_next_memory_node(blob, -1);
+	if (mem < 0) {
+		printf("%s: Missing /memory node\n", __func__);
+		return -EINVAL;
+	}
+
+	for (i = 0; i < MAX_MEM_MAP_REGIONS; i++) {
+		ret = fdt_get_resource(blob, mem, "reg", reg++, &res);
+		if (ret == -FDT_ERR_NOTFOUND) {
+			reg = 0;
+			mem = get_next_memory_node(blob, mem);
+			if (mem == -FDT_ERR_NOTFOUND)
+				break;
+
+			ret = fdt_get_resource(blob, mem, "reg", reg++, &res);
+			if (ret == -FDT_ERR_NOTFOUND)
+				break;
+		}
+		if (ret != 0) {
+			printf("No reg property for memory node\n");
+			return -EINVAL;
+		}
+
+		xen_mem_map[i].virt = (phys_addr_t)res.start;
+		xen_mem_map[i].phys = (phys_addr_t)res.start;
+		xen_mem_map[i].size = (phys_size_t)(res.end - res.start + 1);
+		xen_mem_map[i].attrs = (PTE_BLOCK_MEMTYPE(MT_NORMAL) |
+					PTE_BLOCK_INNER_SHARE);
+	}
+	return 0;
+}
+
+void enable_caches(void)
+{
+	/* Re-setup the memory map as BSS gets cleared after relocation. */
+	setup_mem_map();
+	icache_enable();
+	dcache_enable();
+}
+
+/* Read memory settings from the Xen provided device tree. */
+int dram_init(void)
+{
+	int ret;
+
+	ret = fdtdec_setup_mem_size_base();
+	if (ret < 0)
+		return ret;
+	/* Setup memory map, so MMU page table size can be estimated. */
+	return setup_mem_map();
+}
+
+int dram_init_banksize(void)
+{
+	return fdtdec_setup_memory_banksize();
+}
+
+/*
+ * Board specific reset that is system reset.
+ */
+void reset_cpu(ulong addr)
+{
+}
+
+int ft_system_setup(void *blob, struct bd_info *bd)
+{
+	return 0;
+}
+
+int ft_board_setup(void *blob, struct bd_info *bd)
+{
+	return 0;
+}
+
+int board_early_init_f(void)
+{
+	return 0;
+}
+
+int print_cpuinfo(void)
+{
+	printf("Xen virtual CPU\n");
+	return 0;
+}
+
+__weak struct serial_device *default_serial_console(void)
+{
+	return NULL;
+}
+