hv: a few fixes for multiboot2 boot

- need to specify the load_addr in the multiboot2 address tag. GRUB needs
  it to correctly calculate the ACRN binary's load size if load_end_addr is
  a non-zero value.

- multiboot2 can be enabled if hypervisor relocation is disabled.

- print the name of the boot loader. This might be helpful if the boot
  loader, e.g. GRUB, inludes its version in the name string.

Tracked-On: #4441
Signed-off-by: Victor Sun <victor.sun@intel.com>
Signed-off-by: Zide Chen <zide.chen@intel.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>

hypervisor/Makefile

@@ -111,6 +111,10 @@ ifeq (y, $(CONFIG_MULTIBOOT2))
 ASFLAGS += -DCONFIG_MULTIBOOT2
 endif
 
+ifeq (y, $(CONFIG_RELOC))
+ASFLAGS += -DCONFIG_RELOC
+endif
+
 LDFLAGS += -Wl,--gc-sections -nostartfiles -nostdlib
 LDFLAGS += -Wl,-n,-z,max-page-size=0x1000
 LDFLAGS += -Wl,--no-dynamic-linker

hypervisor/arch/x86/Kconfig

@@ -39,8 +39,7 @@ endchoice
 
 config MULTIBOOT2
 	bool "Multiboot2 support"
-	depends on RELOC
+	default y
-	default n
 	help
 	  Support boot ACRN from multiboot2 protocol. Multiboot2 support is needed for
 	  some EFI platforms to get correct ACPI RSDP, it also could provide host efi

hypervisor/arch/x86/boot/cpu_primary.S

@@ -71,13 +71,14 @@ info_req_tag_start:
     .long   MULTIBOOT2_TAG_TYPE_EFI_MMAP    /* EFI memory map, to be passed to guest Linux */
 info_req_tag_end:
 
+#ifdef CONFIG_RELOC
     .align  MULTIBOOT2_TAG_ALIGN
 address_tag_start:
     .short  MULTIBOOT2_HEADER_TAG_ADDRESS
     .short  0
     .long   address_tag_end - address_tag_start
     .long   mb2_header_start  /* address corresponding to the beginning of the Multiboot2 header */
-    .long   -1  /* load_addr: the file to be loaded from its beginning */
+    .long   _ld_ram_start     /* load_addr: load from the binary's beginning */
     /*
      * load_end_addr: this includes .bss so that boot loader could reserve the
      * memory that .bss occupies to avoid placing boot modules or other data in that area.
@@ -107,13 +108,14 @@ relocatable_tag_start:
     .long   0x200000     /* image alignment */
     .long   1            /* preference: lowest possible address */
 relocatable_tag_end:
+#endif	/* CONFIG_RELOC */
 
     .align     MULTIBOOT2_TAG_ALIGN
     .short  MULTIBOOT2_HEADER_TAG_END
     .short  0
     .long   8
 mb2_header_end:
-#endif
+#endif	/* CONFIG_MULTIBOOT2 */
 
     /*
      * The page tables are aligned to 4KB, which implicitly aligns this section at

hypervisor/boot/guest/vboot_wrapper.c

@@ -42,6 +42,7 @@ void init_vboot(void)
 		{"PXELINUX", DIRECT_BOOT_MODE},
 	};
 
+	printf("Detect bootloader: %s\n", mbi->mi_loader_name);
 	for (i = 0U; i < BOOTLOADER_NUM; i++) {
 		if (strncmp(mbi->mi_loader_name, vboot_bootloader_maps[i].bootloader_name,
 			strnlen_s(vboot_bootloader_maps[i].bootloader_name, BOOTLOADER_NAME_SIZE)) == 0) {

hypervisor/boot/multiboot.c

@@ -68,6 +68,10 @@ int32_t sanitize_multiboot_info(void)
 		ret = -EINVAL;
 	}
 
+	if (acrn_mbi.mi_loader_name[0] == '\0') {
+		pr_err("no bootloader name found!");
+		ret = -EINVAL;
+	}
 	return ret;
 }