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From:   Vitaly Wool <vitaly.wool@konsulko.com>
To:     linux-riscv@lists.infradead.org
Cc:     linux-kernel@vger.kernel.org, Bin Meng <bin.meng@windriver.com>,
        Anup Patel <anup@brainfault.org>,
        Alistair Francis <alistair.francis@wdc.com>,
        Palmer Dabbelt <palmerdabbelt@google.com>,
        Nicolas Pitre <nico@fluxnic.net>,
        Vitaly Wool <vitaly.wool@konsulko.com>
Subject: [PATCH v3] RISC-V: enable XIP
Date:   Mon, 21 Dec 2020 22:37:20 +0200
Message-Id: <20201221203719.15988-1-vitaly.wool@konsulko.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Introduce XIP (eXecute In Place) support for RISC-V platforms.
It allows code to be executed directly from non-volatile storage
directly addressable by the CPU, such as QSPI NOR flash which can
be found on many RISC-V platforms. This makes way for significant
optimization of RAM footprint. The XIP kernel is not compressed
since it has to run directly from flash, so it will occupy more
space on the non-volatile storage to The physical flash address
used to link the kernel object files and for storing it has to
be known at compile time and is represented by a Kconfig option.

XIP on RISC-V will currently only work on MMU-enabled kernels.

Changed in v2:
- dedicated macro for XIP address fixup when MMU is not enabled yet
  o both for 32-bit and 64-bit RISC-V
- SP is explicitly set to a safe place in RAM before __copy_data call
- removed redundant alignment requirements in vmlinux-xip.lds.S
- changed long -> uintptr_t typecast in __XIP_FIXUP macro.

Changed in v3:
- rebased against latest for-next
- XIP address fixup macro now takes an argument
- SMP related fixes
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
---
 arch/riscv/Kconfig                  |  46 ++++++++-
 arch/riscv/Makefile                 |   8 +-
 arch/riscv/boot/Makefile            |  13 +++
 arch/riscv/include/asm/pgtable.h    |  56 +++++++++--
 arch/riscv/kernel/cpu_ops_sbi.c     |   3 +
 arch/riscv/kernel/head.S            |  69 +++++++++++++-
 arch/riscv/kernel/head.h            |   3 +
 arch/riscv/kernel/setup.c           |   8 +-
 arch/riscv/kernel/vmlinux-xip.lds.S | 132 ++++++++++++++++++++++++++
 arch/riscv/kernel/vmlinux.lds.S     |   6 ++
 arch/riscv/mm/init.c                | 142 +++++++++++++++++++++++++---
 11 files changed, 460 insertions(+), 26 deletions(-)
 create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 2b41f6d8e458..fabafdf763da 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -398,7 +398,7 @@ config EFI_STUB
 
 config EFI
 	bool "UEFI runtime support"
-	depends on OF
+	depends on OF && !XIP_KERNEL
 	select LIBFDT
 	select UCS2_STRING
 	select EFI_PARAMS_FROM_FDT
@@ -415,12 +415,52 @@ config EFI
 	  allow the kernel to be booted as an EFI application. This
 	  is only useful on systems that have UEFI firmware.
 
+config XIP_KERNEL
+	bool "Kernel Execute-In-Place from ROM"
+	depends on MMU
+	help
+	  Execute-In-Place allows the kernel to run from non-volatile storage
+	  directly addressable by the CPU, such as NOR flash. This saves RAM
+	  space since the text section of the kernel is not loaded from flash
+	  to RAM.  Read-write sections, such as the data section and stack,
+	  are still copied to RAM.  The XIP kernel is not compressed since
+	  it has to run directly from flash, so it will take more space to
+	  store it.  The flash address used to link the kernel object files,
+	  and for storing it, is configuration dependent. Therefore, if you
+	  say Y here, you must know the proper physical address where to
+	  store the kernel image depending on your own flash memory usage.
+
+	  Also note that the make target becomes "make xipImage" rather than
+	  "make zImage" or "make Image".  The final kernel binary to put in
+	  ROM memory will be arch/riscv/boot/xipImage.
+
+	  If unsure, say N.
+
+config XIP_PHYS_ADDR
+	hex "XIP Kernel Physical Location"
+	depends on XIP_KERNEL
+	default "0x21000000"
+	help
+	  This is the physical address in your flash memory the kernel will
+	  be linked for and stored to.  This address is dependent on your
+	  own flash usage.
+
+config XIP_PHYS_RAM_BASE
+	hex "Platform Physical RAM address"
+	depends on XIP_KERNEL
+	default "0x80000000"
+	help
+	  This is the physical address of RAM in the system. It has to be
+	  explicitly specified to run early relocations of read-write data
+	  from flash to RAM.
 endmenu
 
 config BUILTIN_DTB
-	def_bool n
-	depends on RISCV_M_MODE
+	bool
+	depends on (RISCV_M_MODE || XIP_KERNEL)
 	depends on OF
+	default y if XIP_KERNEL
+	default n if !XIP_KERNEL
 
 menu "Power management options"
 
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 8c29e553ef7f..b89b6897b0be 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -70,7 +70,11 @@ CHECKFLAGS += -D__riscv -D__riscv_xlen=$(BITS)
 
 # Default target when executing plain make
 boot		:= arch/riscv/boot
+ifeq ($(CONFIG_XIP_KERNEL),y)
+KBUILD_IMAGE := $(boot)/xipImage
+else
 KBUILD_IMAGE	:= $(boot)/Image.gz
+endif
 
 head-y := arch/riscv/kernel/head.o
 
@@ -83,12 +87,14 @@ PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
 
+ifneq ($(CONFIG_XIP_KERNEL),y)
 ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_KENDRYTE),yy)
 KBUILD_IMAGE := $(boot)/loader.bin
 else
 KBUILD_IMAGE := $(boot)/Image.gz
 endif
-BOOT_TARGETS := Image Image.gz loader loader.bin
+endif
+BOOT_TARGETS := Image Image.gz loader loader.bin xipImage
 
 all:	$(notdir $(KBUILD_IMAGE))
 
diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
index 03404c84f971..6bf299f70c27 100644
--- a/arch/riscv/boot/Makefile
+++ b/arch/riscv/boot/Makefile
@@ -17,8 +17,21 @@
 KCOV_INSTRUMENT := n
 
 OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
+OBJCOPYFLAGS_xipImage :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
 
 targets := Image Image.* loader loader.o loader.lds loader.bin
+targets := Image Image.* loader loader.o loader.lds loader.bin xipImage
+
+ifeq ($(CONFIG_XIP_KERNEL),y)
+
+quiet_cmd_mkxip = $(quiet_cmd_objcopy)
+cmd_mkxip = $(cmd_objcopy)
+
+$(obj)/xipImage: vmlinux FORCE
+	$(call if_changed,mkxip)
+	@$(kecho) '  Physical Address of xipImage: $(CONFIG_XIP_PHYS_ADDR)'
+
+endif
 
 $(obj)/Image: vmlinux FORCE
 	$(call if_changed,objcopy)
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 183f1f4b2ae6..ec3360363b71 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -11,6 +11,42 @@
 
 #include <asm/pgtable-bits.h>
 
+#ifdef CONFIG_MMU
+
+#define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
+#define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
+
+#ifdef CONFIG_XIP_KERNEL
+/*
+ * Since we use sections to map it, this macro replaces the physical address
+ * with its virtual address while keeping offset from the base section.
+ */
+#define XIP_OFFSET		SZ_8M
+#define XIP_MASK		(SZ_8M - 1)
+#define XIP_VIRT_ADDR(physaddr)	(PAGE_OFFSET - XIP_OFFSET + ((physaddr) & XIP_MASK))
+#define XIP_PHYS_ADDR(va)	 \
+	((uintptr_t)(va) - PAGE_OFFSET + XIP_OFFSET + CONFIG_XIP_PHYS_ADDR)
+#define VMALLOC_END		(PAGE_OFFSET - SZ_16M - 1)
+
+#define XIP_VIRT_ADDR_START	XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
+#define __PHYS_RAM_BASE		CONFIG_XIP_PHYS_RAM_BASE
+
+#define __XIP_FIXUP(addr) \
+	(((uintptr_t)(addr) >= CONFIG_XIP_PHYS_ADDR && \
+	  (uintptr_t)(addr) <= CONFIG_XIP_PHYS_ADDR + SZ_16M) ? \
+	(uintptr_t)(addr) - CONFIG_XIP_PHYS_ADDR + __PHYS_RAM_BASE - XIP_OFFSET : \
+	(uintptr_t)(addr))
+
+#else
+#define VMALLOC_END		(PAGE_OFFSET - 1)
+#endif /* CONFIG_XIP_KERNEL */
+
+#else
+
+#define XIP_VIRT_ADDR(physaddr) physaddr
+
+#endif /* CONFIG_MMU */
+
 #ifndef __ASSEMBLY__
 
 /* Page Upper Directory not used in RISC-V */
@@ -21,10 +57,6 @@
 
 #ifdef CONFIG_MMU
 
-#define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
-#define VMALLOC_END      (PAGE_OFFSET - 1)
-#define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
-
 #define BPF_JIT_REGION_SIZE	(SZ_128M)
 #define BPF_JIT_REGION_START	(PAGE_OFFSET - BPF_JIT_REGION_SIZE)
 #define BPF_JIT_REGION_END	(VMALLOC_END)
@@ -467,8 +499,20 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
 
 #define kern_addr_valid(addr)   (1) /* FIXME */
 
-extern void *dtb_early_va;
-extern uintptr_t dtb_early_pa;
+extern void *_dtb_early_va;
+extern uintptr_t _dtb_early_pa;
+#if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_MMU)
+
+#define dtb_early_va	(*(void **)__XIP_FIXUP(&_dtb_early_va))
+#define dtb_early_pa	(*(uintptr_t *)__XIP_FIXUP(&_dtb_early_pa))
+
+#else
+
+#define dtb_early_va	_dtb_early_va
+#define dtb_early_pa	_dtb_early_pa
+
+#endif /* CONFIG_XIP_KERNEL */
+
 void setup_bootmem(void);
 void paging_init(void);
 
diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c
index 685fae72b7f5..9c8d6dab55b8 100644
--- a/arch/riscv/kernel/cpu_ops_sbi.c
+++ b/arch/riscv/kernel/cpu_ops_sbi.c
@@ -59,6 +59,9 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
 	unsigned long boot_addr = __pa_symbol(secondary_start_sbi);
 	int hartid = cpuid_to_hartid_map(cpuid);
 
+#ifdef CONFIG_XIP_KERNEL
+	boot_addr = XIP_PHYS_ADDR(secondary_start_sbi);
+#endif
 	cpu_update_secondary_bootdata(cpuid, tidle);
 	rc = sbi_hsm_hart_start(hartid, boot_addr, 0);
 
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 45dbdae930bf..6f065a5502d3 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -9,11 +9,31 @@
 #include <linux/linkage.h>
 #include <asm/thread_info.h>
 #include <asm/page.h>
+#include <asm/pgtable.h>
 #include <asm/csr.h>
 #include <asm/hwcap.h>
 #include <asm/image.h>
 #include "efi-header.S"
 
+#ifdef CONFIG_XIP_KERNEL
+.macro XIP_FIXUP_OFFSET reg
+#ifdef CONFIG_64BIT
+		ld t0, _xip_fixup
+#else
+		lw t0, _xip_fixup
+#endif
+		add \reg, \reg, t0
+.endm
+
+_xip_fixup:
+#ifdef CONFIG_64BIT
+	.dword CONFIG_XIP_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
+#else
+	.word CONFIG_XIP_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
+#endif
+
+#endif /* CONFIG_XIP_KERNEL */
+
 __HEAD
 ENTRY(_start)
 	/*
@@ -64,7 +84,11 @@ pe_head_start:
 #ifdef CONFIG_MMU
 relocate:
 	/* Relocate return address */
+#ifdef CONFIG_XIP_KERNEL
+	li a1, XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
+#else
 	li a1, PAGE_OFFSET
+#endif
 	la a2, _start
 	sub a1, a1, a2
 	add ra, ra, a1
@@ -85,7 +109,12 @@ relocate:
 	 * full fence here because setup_vm() just wrote these PTEs and we need
 	 * to ensure the new translations are in use.
 	 */
+#ifdef CONFIG_XIP_KERNEL
+	la a0, _trampoline_pg_dir
+	XIP_FIXUP_OFFSET a0
+#else
 	la a0, trampoline_pg_dir
+#endif
 	srl a0, a0, PAGE_SHIFT
 	or a0, a0, a1
 	sfence.vma
@@ -140,6 +169,10 @@ secondary_start_sbi:
 	slli a3, a0, LGREG
 	la a4, __cpu_up_stack_pointer
 	la a5, __cpu_up_task_pointer
+#ifdef CONFIG_XIP_KERNEL
+	XIP_FIXUP_OFFSET a4
+	XIP_FIXUP_OFFSET a5
+#endif
 	add a4, a3, a4
 	add a5, a3, a5
 	REG_L sp, (a4)
@@ -233,10 +266,24 @@ pmp_done:
 
 	/* Pick one hart to run the main boot sequence */
 	la a3, hart_lottery
+#ifdef CONFIG_XIP_KERNEL
+	XIP_FIXUP_OFFSET a3
+#endif
 	li a2, 1
 	amoadd.w a3, a2, (a3)
 	bnez a3, .Lsecondary_start
 
+#ifdef CONFIG_XIP_KERNEL
+	la sp, _end + THREAD_SIZE
+	XIP_FIXUP_OFFSET sp
+	mv s0, a0
+	call __copy_data
+
+	/* Restore a0 copy */
+	mv a0, s0
+#endif
+
+#ifndef CONFIG_XIP_KERNEL
 	/* Clear BSS for flat non-ELF images */
 	la a3, __bss_start
 	la a4, __bss_stop
@@ -246,19 +293,35 @@ clear_bss:
 	add a3, a3, RISCV_SZPTR
 	blt a3, a4, clear_bss
 clear_bss_done:
-
+#endif
 	/* Save hart ID and DTB physical address */
 	mv s0, a0
 	mv s1, a1
+
 	la a2, boot_cpu_hartid
+#ifdef CONFIG_XIP_KERNEL
+	XIP_FIXUP_OFFSET a2
+#endif
 	REG_S a0, (a2)
 
 	/* Initialize page tables and relocate to virtual addresses */
 	la sp, init_thread_union + THREAD_SIZE
+#ifdef CONFIG_XIP_KERNEL
+	XIP_FIXUP_OFFSET sp
+#endif
+#if defined (CONFIG_XIP_KERNEL) && defined (CONFIG_BUILTIN_DTB)
+	la a0, __dtb_start
+#else
 	mv a0, s1
+#endif
 	call setup_vm
 #ifdef CONFIG_MMU
+#ifdef CONFIG_XIP_KERNEL
+	la a0, _early_pg_dir
+	XIP_FIXUP_OFFSET a0
+#else
 	la a0, early_pg_dir
+#endif
 	call relocate
 #endif /* CONFIG_MMU */
 
@@ -284,6 +347,10 @@ clear_bss_done:
 	slli a3, a0, LGREG
 	la a1, __cpu_up_stack_pointer
 	la a2, __cpu_up_task_pointer
+#ifdef CONFIG_XIP_KERNEL
+	XIP_FIXUP_OFFSET a1
+	XIP_FIXUP_OFFSET a2
+#endif
 	add a1, a3, a1
 	add a2, a3, a2
 
diff --git a/arch/riscv/kernel/head.h b/arch/riscv/kernel/head.h
index b48dda3d04f6..aabbc3ac3e48 100644
--- a/arch/riscv/kernel/head.h
+++ b/arch/riscv/kernel/head.h
@@ -12,6 +12,9 @@ extern atomic_t hart_lottery;
 
 asmlinkage void do_page_fault(struct pt_regs *regs);
 asmlinkage void __init setup_vm(uintptr_t dtb_pa);
+#ifdef CONFIG_XIP_KERNEL
+asmlinkage void __init __copy_data(void);
+#endif
 
 extern void *__cpu_up_stack_pointer[];
 extern void *__cpu_up_task_pointer[];
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index a834deab31d3..876d4ff0ecc4 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -50,7 +50,11 @@ struct screen_info screen_info __section(".data") = {
  * This is used before the kernel initializes the BSS so it can't be in the
  * BSS.
  */
-atomic_t hart_lottery __section(".sdata");
+atomic_t hart_lottery __section(".sdata")
+#ifdef CONFIG_XIP_KERNEL
+= ATOMIC_INIT(1)
+#endif
+;
 unsigned long boot_cpu_hartid;
 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 
@@ -244,7 +248,7 @@ void __init setup_arch(char **cmdline_p)
 #if IS_ENABLED(CONFIG_BUILTIN_DTB)
 	unflatten_and_copy_device_tree();
 #else
-	if (early_init_dt_verify(__va(dtb_early_pa)))
+	if (early_init_dt_verify(dtb_early_va))
 		unflatten_device_tree();
 	else
 		pr_err("No DTB found in kernel mappings\n");
diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
new file mode 100644
index 000000000000..9f0f08c34cd3
--- /dev/null
+++ b/arch/riscv/kernel/vmlinux-xip.lds.S
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ * Copyright (C) 2020 Vitaly Wool, Konsulko AB
+ */
+
+#define LOAD_OFFSET XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR)
+/* No __ro_after_init data in the .rodata section - which will always be ro */
+#define RO_AFTER_INIT_DATA
+
+#include <asm/vmlinux.lds.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/cache.h>
+#include <asm/thread_info.h>
+
+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+
+jiffies = jiffies_64;
+
+SECTIONS
+{
+	/* Beginning of code and text segment */
+	. = XIP_VIRT_ADDR(CONFIG_XIP_PHYS_ADDR);
+	_xiprom = .;
+	_start = .;
+	HEAD_TEXT_SECTION
+	INIT_TEXT_SECTION(PAGE_SIZE)
+	/* we have to discard exit text and such at runtime, not link time */
+	.exit.text :
+	{
+		EXIT_TEXT
+	}
+
+	.text : {
+		_text = .;
+		_stext = .;
+		TEXT_TEXT
+		SCHED_TEXT
+		CPUIDLE_TEXT
+		LOCK_TEXT
+		KPROBES_TEXT
+		ENTRY_TEXT
+		IRQENTRY_TEXT
+		SOFTIRQENTRY_TEXT
+		*(.fixup)
+		_etext = .;
+	}
+	RO_DATA(L1_CACHE_BYTES)
+	.srodata : {
+		*(.srodata*)
+	}
+	.init.rodata : {
+		INIT_SETUP(16)
+		INIT_CALLS
+		CON_INITCALL
+		INIT_RAM_FS
+	}
+	_exiprom = .;			/* End of XIP ROM area */
+
+
+/*
+ * From this point, stuff is considered writable and will be copied to RAM
+ */
+	__data_loc = ALIGN(16);		/* location in file */
+	. = PAGE_OFFSET;		/* location in memory */
+
+	_sdata = .;			/* Start of data section */
+	_data = .;
+	RW_DATA(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
+	_edata = .;
+	__start_ro_after_init = .;
+	.data.ro_after_init : AT(ADDR(.data.ro_after_init) - LOAD_OFFSET) {
+		*(.data..ro_after_init)
+	}
+	__end_ro_after_init = .;
+
+	. = ALIGN(PAGE_SIZE);
+	__init_begin = .;
+	.init.data : {
+		INIT_DATA
+	}
+	.exit.data : {
+		EXIT_DATA
+	}
+	. = ALIGN(8);
+	__soc_early_init_table : {
+		__soc_early_init_table_start = .;
+		KEEP(*(__soc_early_init_table))
+		__soc_early_init_table_end = .;
+	}
+	__soc_builtin_dtb_table : {
+		__soc_builtin_dtb_table_start = .;
+		KEEP(*(__soc_builtin_dtb_table))
+		__soc_builtin_dtb_table_end = .;
+	}
+	PERCPU_SECTION(L1_CACHE_BYTES)
+
+	. = ALIGN(PAGE_SIZE);
+	__init_end = .;
+
+	.sdata : {
+		__global_pointer$ = . + 0x800;
+		*(.sdata*)
+		*(.sbss*)
+	}
+
+	BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)
+	EXCEPTION_TABLE(0x10)
+
+	.rel.dyn : AT(ADDR(.rel.dyn) - LOAD_OFFSET) {
+		*(.rel.dyn*)
+	}
+
+	/*
+	 * End of copied data. We need a dummy section to get its LMA.
+	 * Also located before final ALIGN() as trailing padding is not stored
+	 * in the resulting binary file and useless to copy.
+	 */
+	.data.endmark : AT(ADDR(.data.endmark) - LOAD_OFFSET) { }
+	_edata_loc = LOADADDR(.data.endmark);
+
+	. = ALIGN(PAGE_SIZE);
+	_end = .;
+
+	STABS_DEBUG
+	DWARF_DEBUG
+
+	DISCARDS
+}
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index de03cb22d0e9..6745ec325930 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -4,7 +4,12 @@
  * Copyright (C) 2017 SiFive
  */
 
+#ifdef CONFIG_XIP_KERNEL
+#include "vmlinux-xip.lds.S"
+#else
+
 #define LOAD_OFFSET PAGE_OFFSET
+
 #include <asm/vmlinux.lds.h>
 #include <asm/page.h>
 #include <asm/cache.h>
@@ -132,3 +137,4 @@ SECTIONS
 
 	DISCARDS
 }
+#endif /* CONFIG_XIP_KERNEL */
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 87c305c566ac..8636432400df 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -30,8 +30,8 @@ EXPORT_SYMBOL(empty_zero_page);
 
 extern char _start[];
 #define DTB_EARLY_BASE_VA      PGDIR_SIZE
-void *dtb_early_va __initdata;
-uintptr_t dtb_early_pa __initdata;
+void *_dtb_early_va __initdata;
+uintptr_t _dtb_early_pa __initdata;
 
 struct pt_alloc_ops {
 	pte_t *(*get_pte_virt)(phys_addr_t pa);
@@ -87,6 +87,10 @@ static void print_vm_layout(void)
 		  (unsigned long)VMALLOC_END);
 	print_mlm("lowmem", (unsigned long)PAGE_OFFSET,
 		  (unsigned long)high_memory);
+#ifdef CONFIG_XIP_KERNEL
+	print_mlm("xip", (unsigned long)XIP_VIRT_ADDR_START,
+		  (unsigned long)XIP_VIRT_ADDR_START + SZ_16M);
+#endif /* CONFIG_XIP_KERNEL */
 }
 #else
 static void print_vm_layout(void) { }
@@ -163,6 +167,10 @@ void __init setup_bootmem(void)
 	phys_addr_t vmlinux_start = __pa_symbol(&_start);
 	u64 i;
 
+#ifdef CONFIG_XIP_KERNEL
+	vmlinux_start = __pa_symbol(&_sdata);
+#endif
+
 	/* Find the memory region containing the kernel */
 	for_each_mem_range(i, &start, &end) {
 		phys_addr_t size = end - start;
@@ -194,11 +202,18 @@ void __init setup_bootmem(void)
 	setup_initrd();
 #endif /* CONFIG_BLK_DEV_INITRD */
 
-	/*
-	 * Avoid using early_init_fdt_reserve_self() since __pa() does
-	 * not work for DTB pointers that are fixmap addresses
-	 */
-	memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
+#ifdef CONFIG_XIP_KERNEL
+	if (dtb_early_pa < CONFIG_XIP_PHYS_ADDR ||
+	    dtb_early_pa > CONFIG_XIP_PHYS_ADDR + SZ_16M)
+#endif
+	{
+		/*
+		 * Avoid using early_init_fdt_reserve_self() since __pa() does
+		 * not work for DTB pointers that are fixmap addresses
+		 */
+		memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
+		dtb_early_va = __va(dtb_early_pa);
+	}
 
 	early_init_fdt_scan_reserved_mem();
 	dma_contiguous_reserve(dma32_phys_limit);
@@ -206,21 +221,47 @@ void __init setup_bootmem(void)
 	memblock_dump_all();
 }
 
+#ifdef CONFIG_XIP_KERNEL
+
+extern char _xiprom[], _exiprom[];
+extern char _sdata[], _edata[];
+
+#endif /* CONFIG_XIP_KERNEL */
+
 #ifdef CONFIG_MMU
-static struct pt_alloc_ops pt_ops;
+static struct pt_alloc_ops _pt_ops;
+
+#ifdef CONFIG_XIP_KERNEL
+#define pt_ops (*(struct pt_alloc_ops *)__XIP_FIXUP(&_pt_ops))
+#else
+#define pt_ops	_pt_ops
+#endif
 
 unsigned long va_pa_offset;
 EXPORT_SYMBOL(va_pa_offset);
+#ifdef CONFIG_XIP_KERNEL
+#define va_pa_offset	(*((unsigned long *)__XIP_FIXUP(&va_pa_offset)))
+#endif
 unsigned long pfn_base;
 EXPORT_SYMBOL(pfn_base);
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
-pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
-pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
 
 #define MAX_EARLY_MAPPING_SIZE	SZ_128M
 
+#ifdef CONFIG_XIP_KERNEL
+pgd_t _trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
+pte_t _fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
+pgd_t _early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+
+#define trampoline_pg_dir	((pgd_t *)__XIP_FIXUP(_trampoline_pg_dir))
+#define fixmap_pte		((pte_t *)__XIP_FIXUP(_fixmap_pte))
+#define early_pg_dir		((pgd_t *)__XIP_FIXUP(_early_pg_dir))
+#else
+pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
+pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
 pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
+#endif /* CONFIG_XIP_KERNEL */
 
 void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
 {
@@ -292,15 +333,27 @@ static void __init create_pte_mapping(pte_t *ptep,
 
 #ifndef __PAGETABLE_PMD_FOLDED
 
-pmd_t trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
-pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
-
 #if MAX_EARLY_MAPPING_SIZE < PGDIR_SIZE
 #define NUM_EARLY_PMDS		1UL
 #else
 #define NUM_EARLY_PMDS		(1UL + MAX_EARLY_MAPPING_SIZE / PGDIR_SIZE)
 #endif
+
+#ifdef CONFIG_XIP_KERNEL
+pmd_t _trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
+pmd_t _fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
+pmd_t _xip_pmd[PTRS_PER_PGD * NUM_EARLY_PMDS] __page_aligned_bss;
+pmd_t _early_pmd[PTRS_PER_PMD * NUM_EARLY_PMDS] __initdata __aligned(PAGE_SIZE);
+
+#define trampoline_pmd	((pmd_t *)__XIP_FIXUP(_trampoline_pmd))
+#define fixmap_pmd	((pmd_t *)__XIP_FIXUP(_fixmap_pmd))
+#define xip_pmd		((pmd_t *)__XIP_FIXUP(_xip_pmd))
+#define early_pmd	((pmd_t *)__XIP_FIXUP(_early_pmd))
+#else
+pmd_t trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
+pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
 pmd_t early_pmd[PTRS_PER_PMD * NUM_EARLY_PMDS] __initdata __aligned(PAGE_SIZE);
+#endif
 
 static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
 {
@@ -420,6 +473,19 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
 	return PMD_SIZE;
 }
 
+#ifdef CONFIG_XIP_KERNEL
+/* called from head.S with MMU off */
+asmlinkage void __init __copy_data(void)
+{
+	void *from = (void *)(&_sdata);
+	void *end = (void *)(&_end);
+	void *to = (void *)CONFIG_XIP_PHYS_RAM_BASE;
+	size_t sz = (size_t)(end - from);
+
+	memcpy(to, from, sz);
+}
+#endif
+
 /*
  * setup_vm() is called from head.S with MMU-off.
  *
@@ -448,6 +514,19 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	pmd_t fix_bmap_spmd, fix_bmap_epmd;
 #endif
 
+#ifdef CONFIG_XIP_KERNEL
+	uintptr_t xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
+	uintptr_t xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
+	uintptr_t xip_map_size = best_map_size(xiprom,
+					       MAX_EARLY_MAPPING_SIZE);
+
+	BUG_ON((xiprom % xip_map_size) != 0);
+	BUG_ON(xiprom_sz > MAX_EARLY_MAPPING_SIZE);
+
+	load_pa = (uintptr_t)CONFIG_XIP_PHYS_RAM_BASE;
+	load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
+	map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
+#endif
 	va_pa_offset = PAGE_OFFSET - load_pa;
 	pfn_base = PFN_DOWN(load_pa);
 
@@ -487,6 +566,21 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 			   load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
 #endif
 
+#ifdef CONFIG_XIP_KERNEL
+	create_pgd_mapping(trampoline_pg_dir, XIP_VIRT_ADDR_START,
+			   (uintptr_t)xip_pmd, PGDIR_SIZE, PAGE_TABLE);
+	for (va = XIP_VIRT_ADDR_START;
+	     va < XIP_VIRT_ADDR_START + xiprom_sz;
+	     va += PMD_SIZE) {
+		create_pmd_mapping(xip_pmd, va,
+				   xiprom + (va - XIP_VIRT_ADDR_START),
+				   PMD_SIZE, PAGE_KERNEL_EXEC);
+	}
+
+	create_pgd_mapping(early_pg_dir, XIP_VIRT_ADDR_START,
+			   (uintptr_t)xip_pmd, PGDIR_SIZE, PAGE_TABLE);
+#endif
+
 	/*
 	 * Setup early PGD covering entire kernel which will allows
 	 * us to reach paging_init(). We map all memory banks later
@@ -543,6 +637,9 @@ static void __init setup_vm_final(void)
 	uintptr_t va, map_size;
 	phys_addr_t pa, start, end;
 	u64 i;
+#ifdef CONFIG_XIP_KERNEL
+	uintptr_t xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
+#endif
 
 	/**
 	 * MMU is enabled at this point. But page table setup is not complete yet.
@@ -574,6 +671,25 @@ static void __init setup_vm_final(void)
 					   map_size, PAGE_KERNEL_EXEC);
 		}
 	}
+#ifdef CONFIG_XIP_KERNEL
+	for (va = XIP_VIRT_ADDR_START;
+	     va < XIP_VIRT_ADDR_START + xiprom_sz;
+	     va += PMD_SIZE)
+		create_pgd_mapping(swapper_pg_dir, va,
+				   CONFIG_XIP_PHYS_ADDR + (va - XIP_VIRT_ADDR_START),
+				   PMD_SIZE, PAGE_KERNEL_EXEC);
+
+	/* if DT is in NOR, keep the early mapping */
+	if (dtb_early_pa >= CONFIG_XIP_PHYS_ADDR &&
+	    dtb_early_pa <= CONFIG_XIP_PHYS_ADDR + SZ_16M) {
+		pa = dtb_early_pa & ~(PGDIR_SIZE - 1);
+		va = DTB_EARLY_BASE_VA;
+		create_pgd_mapping(swapper_pg_dir, va,
+				   pa, PGDIR_SIZE, PAGE_KERNEL);
+		create_pgd_mapping(swapper_pg_dir, va + PGDIR_SIZE,
+				   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
+	}
+#endif
 
 	/* Clear fixmap PTE and PMD mappings */
 	clear_fixmap(FIX_PTE);
-- 
2.29.2