x86/boot: Mostly revert commit ae7e1238e68f2a ("Add ACPI RSDP address to setup_header")

Peter Anvin pointed out that commit:

  ae7e1238e68f2a ("x86/boot: Add ACPI RSDP address to setup_header")

should be reverted as setup_header should only contain items set by the
legacy BIOS.

So revert said commit. Instead of fully reverting the dependent commit
of:

  e7b66d16fe4172 ("x86/acpi, x86/boot: Take RSDP address for boot params if available")

just remove the setup_header reference in order to replace it by
a boot_params in a followup patch.

Suggested-by: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boris.ostrovsky@oracle.com
Cc: bp@alien8.de
Cc: daniel.kiper@oracle.com
Cc: sstabellini@kernel.org
Cc: xen-devel@lists.xenproject.org
Link: http://lkml.kernel.org/r/20181120072529.5489-2-jgross@suse.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/x86/boot.txt

@@ -61,18 +61,6 @@ Protocol 2.12:	(Kernel 3.8) Added the xloadflags field and extension fields
 	 	to struct boot_params for loading bzImage and ramdisk
 		above 4G in 64bit.
 
-Protocol 2.13:	(Kernel 3.14) Support 32- and 64-bit flags being set in
-		xloadflags to support booting a 64-bit kernel from 32-bit
-		EFI
-
-Protocol 2.14:	(Kernel 4.20) Added acpi_rsdp_addr holding the physical
-		address of the ACPI RSDP table.
-		The bootloader updates version with:
-		0x8000 | min(kernel-version, bootloader-version)
-		kernel-version being the protocol version supported by
-		the kernel and bootloader-version the protocol version
-		supported by the bootloader.
-
 **** MEMORY LAYOUT
 
 The traditional memory map for the kernel loader, used for Image or
@@ -209,7 +197,6 @@ Offset	Proto	Name		Meaning
 0258/8	2.10+	pref_address	Preferred loading address
 0260/4	2.10+	init_size	Linear memory required during initialization
 0264/4	2.11+	handover_offset	Offset of handover entry point
-0268/8	2.14+	acpi_rsdp_addr	Physical address of RSDP table
 
 (1) For backwards compatibility, if the setup_sects field contains 0, the
     real value is 4.
@@ -322,7 +309,7 @@ Protocol:	2.00+
   Contains the magic number "HdrS" (0x53726448).
 
 Field name:	version
-Type:		modify
+Type:		read
 Offset/size:	0x206/2
 Protocol:	2.00+
 
@@ -330,12 +317,6 @@ Protocol:	2.00+
   e.g. 0x0204 for version 2.04, and 0x0a11 for a hypothetical version
   10.17.
 
-  Up to protocol version 2.13 this information is only read by the
-  bootloader. From protocol version 2.14 onwards the bootloader will
-  write the used protocol version or-ed with 0x8000 to the field. The
-  used protocol version will be the minimum of the supported protocol
-  versions of the bootloader and the kernel.
-
 Field name:	realmode_swtch
 Type:		modify (optional)
 Offset/size:	0x208/4
@@ -763,17 +744,6 @@ Offset/size:	0x264/4
 
   See EFI HANDOVER PROTOCOL below for more details.
 
-Field name:	acpi_rsdp_addr
-Type:		write
-Offset/size:	0x268/8
-Protocol:	2.14+
-
-  This field can be set by the boot loader to tell the kernel the
-  physical address of the ACPI RSDP table.
-
-  A value of 0 indicates the kernel should fall back to the standard
-  methods to locate the RSDP.
-
 
 **** THE IMAGE CHECKSUM
 

arch/x86/boot/header.S

@@ -300,7 +300,7 @@ _start:
 	# Part 2 of the header, from the old setup.S
 
 		.ascii	"HdrS"		# header signature
-		.word	0x020e		# header version number (>= 0x0105)
+		.word	0x020d		# header version number (>= 0x0105)
 					# or else old loadlin-1.5 will fail)
 		.globl realmode_swtch
 realmode_swtch:	.word	0, 0		# default_switch, SETUPSEG
@@ -558,10 +558,6 @@ pref_address:		.quad LOAD_PHYSICAL_ADDR	# preferred load addr
 init_size:		.long INIT_SIZE		# kernel initialization size
 handover_offset:	.long 0			# Filled in by build.c
 
-acpi_rsdp_addr:		.quad 0			# 64-bit physical pointer to the
-						# ACPI RSDP table, added with
-						# version 2.14
-
 # End of setup header #####################################################
 
 	.section ".entrytext", "ax"

arch/x86/include/asm/x86_init.h

@@ -303,6 +303,4 @@ extern void x86_init_noop(void);
 extern void x86_init_uint_noop(unsigned int unused);
 extern bool x86_pnpbios_disabled(void);
 
-void x86_verify_bootdata_version(void);
-
 #endif

arch/x86/include/uapi/asm/bootparam.h

@@ -16,9 +16,6 @@
 #define RAMDISK_PROMPT_FLAG		0x8000
 #define RAMDISK_LOAD_FLAG		0x4000
 
-/* version flags */
-#define VERSION_WRITTEN	0x8000
-
 /* loadflags */
 #define LOADED_HIGH	(1<<0)
 #define KASLR_FLAG	(1<<1)
@@ -89,7 +86,6 @@ struct setup_header {
 	__u64	pref_address;
 	__u32	init_size;
 	__u32	handover_offset;
-	__u64	acpi_rsdp_addr;
 } __attribute__((packed));
 
 struct sys_desc_table {

arch/x86/kernel/acpi/boot.c

@@ -1776,5 +1776,5 @@ void __init arch_reserve_mem_area(acpi_physical_address addr, size_t size)
 
 u64 x86_default_get_root_pointer(void)
 {
-	return boot_params.hdr.acpi_rsdp_addr;
+	return 0;
 }

arch/x86/kernel/head32.c

@@ -37,7 +37,6 @@ asmlinkage __visible void __init i386_start_kernel(void)
 	cr4_init_shadow();
 
 	sanitize_boot_params(&boot_params);
-	x86_verify_bootdata_version();
 
 	x86_early_init_platform_quirks();
 

arch/x86/kernel/head64.c

@@ -457,8 +457,6 @@ void __init x86_64_start_reservations(char *real_mode_data)
 	if (!boot_params.hdr.version)
 		copy_bootdata(__va(real_mode_data));
 
-	x86_verify_bootdata_version();
-
 	x86_early_init_platform_quirks();
 
 	switch (boot_params.hdr.hardware_subarch) {

arch/x86/kernel/setup.c

@@ -1280,23 +1280,6 @@ void __init setup_arch(char **cmdline_p)
 	unwind_init();
 }
 
-/*
- * From boot protocol 2.14 onwards we expect the bootloader to set the
- * version to "0x8000 | <used version>". In case we find a version >= 2.14
- * without the 0x8000 we assume the boot loader supports 2.13 only and
- * reset the version accordingly. The 0x8000 flag is removed in any case.
- */
-void __init x86_verify_bootdata_version(void)
-{
-	if (boot_params.hdr.version & VERSION_WRITTEN)
-		boot_params.hdr.version &= ~VERSION_WRITTEN;
-	else if (boot_params.hdr.version >= 0x020e)
-		boot_params.hdr.version = 0x020d;
-
-	if (boot_params.hdr.version < 0x020e)
-		boot_params.hdr.acpi_rsdp_addr = 0;
-}
-
 #ifdef CONFIG_X86_32
 
 static struct resource video_ram_resource = {