[v7] RISC-V: enable XIP
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Message ID 20210409065115.11054-1-alex@ghiti.fr
State New
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  • [v7] RISC-V: enable XIP
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Commit Message

Alex Ghiti April 9, 2021, 6:51 a.m. UTC
From: Vitaly Wool <vitaly.wool@konsulko.com>

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. 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 for the time being only work on MMU-enabled
kernels.

Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> [ Rebase on top of "Move
kernel mapping outside the linear mapping ]
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
---

Changes 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.
Changes in v3:
- rebased against latest for-next
- XIP address fixup macro now takes an argument
- SMP related fixes
Changes in v4:
- rebased against the current for-next
- less #ifdef's in C/ASM code
- dedicated XIP_FIXUP_OFFSET assembler macro in head.S
- C-specific definitions moved into #ifndef __ASSEMBLY__
- Fixed multi-core boot
Changes in v5:
- fixed build error for non-XIP kernels
Changes in v6:
- XIP_PHYS_RAM_BASE config option renamed to PHYS_RAM_BASE
- added PHYS_RAM_BASE_FIXED config flag to allow usage of
  PHYS_RAM_BASE in non-XIP configurations if needed
- XIP_FIXUP macro rewritten with a tempoarary variable to avoid side
  effects
- fixed crash for non-XIP kernels that don't use built-in DTB
Changes in v7:
- Fix pfn_base that required FIXUP
- Fix copy_data which lacked + 1 in size to copy
- Fix pfn_valid for FLATMEM
- Rebased on top of "Move kernel mapping outside the linear mapping":
  this is the biggest change and affected mm/init.c,
  kernel/vmlinux-xip.lds.S and include/asm/pgtable.h: XIP kernel is now
  mapped like 'normal' kernel at the end of the address space.

 arch/riscv/Kconfig                  |  51 ++++++++++-
 arch/riscv/Makefile                 |   8 +-
 arch/riscv/boot/Makefile            |  13 +++
 arch/riscv/include/asm/page.h       |  28 ++++++
 arch/riscv/include/asm/pgtable.h    |  25 +++++-
 arch/riscv/kernel/head.S            |  46 +++++++++-
 arch/riscv/kernel/head.h            |   3 +
 arch/riscv/kernel/setup.c           |  10 ++-
 arch/riscv/kernel/vmlinux-xip.lds.S | 133 ++++++++++++++++++++++++++++
 arch/riscv/kernel/vmlinux.lds.S     |   6 ++
 arch/riscv/mm/init.c                | 118 ++++++++++++++++++++++--
 11 files changed, 424 insertions(+), 17 deletions(-)
 create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S

Comments

Alex Ghiti April 9, 2021, 7:14 a.m. UTC | #1
Le 4/9/21 à 2:51 AM, Alexandre Ghiti a écrit :
> From: Vitaly Wool <vitaly.wool@konsulko.com>
> 
> 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. 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 for the time being only work on MMU-enabled
> kernels.
>
I added linux-mm and linux-arch to get feedbacks because I noticed that 
DEBUG_VM_PGTABLE fails for SPARSEMEM (it works for FLATMEM but I think 
it does not do what is expected): the fact that we don't have any struct 
page to back the text and rodata in flash is the problem but to which 
extent ?

Thanks,

Alex

> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> [ Rebase on top of "Move
> kernel mapping outside the linear mapping ]
> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
> ---
> 
> Changes 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.
> Changes in v3:
> - rebased against latest for-next
> - XIP address fixup macro now takes an argument
> - SMP related fixes
> Changes in v4:
> - rebased against the current for-next
> - less #ifdef's in C/ASM code
> - dedicated XIP_FIXUP_OFFSET assembler macro in head.S
> - C-specific definitions moved into #ifndef __ASSEMBLY__
> - Fixed multi-core boot
> Changes in v5:
> - fixed build error for non-XIP kernels
> Changes in v6:
> - XIP_PHYS_RAM_BASE config option renamed to PHYS_RAM_BASE
> - added PHYS_RAM_BASE_FIXED config flag to allow usage of
>    PHYS_RAM_BASE in non-XIP configurations if needed
> - XIP_FIXUP macro rewritten with a tempoarary variable to avoid side
>    effects
> - fixed crash for non-XIP kernels that don't use built-in DTB
> Changes in v7:
> - Fix pfn_base that required FIXUP
> - Fix copy_data which lacked + 1 in size to copy
> - Fix pfn_valid for FLATMEM
> - Rebased on top of "Move kernel mapping outside the linear mapping":
>    this is the biggest change and affected mm/init.c,
>    kernel/vmlinux-xip.lds.S and include/asm/pgtable.h: XIP kernel is now
>    mapped like 'normal' kernel at the end of the address space.
> 
>   arch/riscv/Kconfig                  |  51 ++++++++++-
>   arch/riscv/Makefile                 |   8 +-
>   arch/riscv/boot/Makefile            |  13 +++
>   arch/riscv/include/asm/page.h       |  28 ++++++
>   arch/riscv/include/asm/pgtable.h    |  25 +++++-
>   arch/riscv/kernel/head.S            |  46 +++++++++-
>   arch/riscv/kernel/head.h            |   3 +
>   arch/riscv/kernel/setup.c           |  10 ++-
>   arch/riscv/kernel/vmlinux-xip.lds.S | 133 ++++++++++++++++++++++++++++
>   arch/riscv/kernel/vmlinux.lds.S     |   6 ++
>   arch/riscv/mm/init.c                | 118 ++++++++++++++++++++++--
>   11 files changed, 424 insertions(+), 17 deletions(-)
>   create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 8ea60a0a19ae..4d0153805927 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -28,7 +28,7 @@ config RISCV
>   	select ARCH_HAS_PTE_SPECIAL
>   	select ARCH_HAS_SET_DIRECT_MAP
>   	select ARCH_HAS_SET_MEMORY
> -	select ARCH_HAS_STRICT_KERNEL_RWX if MMU
> +	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>   	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>   	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>   	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> @@ -441,7 +441,7 @@ 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
> @@ -465,11 +465,56 @@ config STACKPROTECTOR_PER_TASK
>   	def_bool y
>   	depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
>   
> +config PHYS_RAM_BASE_FIXED
> +	bool "Explicitly specified physical RAM address"
> +	default n
> +
> +config PHYS_RAM_BASE
> +	hex "Platform Physical RAM address"
> +	depends on PHYS_RAM_BASE_FIXED
> +	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.
> +
> +config XIP_KERNEL
> +	bool "Kernel Execute-In-Place from ROM"
> +	depends on MMU
> +	select PHYS_RAM_BASE_FIXED
> +	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.
> +
>   endmenu
>   
>   config BUILTIN_DTB
> -	def_bool n
> +	bool
>   	depends on OF
> +	default y if XIP_KERNEL
>   
>   menu "Power management options"
>   
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index 1368d943f1f3..8fcbec03974d 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -82,7 +82,11 @@ 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
>   
> @@ -95,12 +99,14 @@ PHONY += vdso_install
>   vdso_install:
>   	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
>   
> +ifneq ($(CONFIG_XIP_KERNEL),y)
>   ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),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/page.h b/arch/riscv/include/asm/page.h
> index 22cfb2be60dc..6fe0ff8c8fa9 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -91,6 +91,9 @@ typedef struct page *pgtable_t;
>   #ifdef CONFIG_MMU
>   extern unsigned long va_pa_offset;
>   extern unsigned long va_kernel_pa_offset;
> +#ifdef CONFIG_XIP_KERNEL
> +extern unsigned long va_kernel_xip_pa_offset;
> +#endif
>   extern unsigned long pfn_base;
>   #define ARCH_PFN_OFFSET		(pfn_base)
>   #else
> @@ -102,11 +105,29 @@ extern unsigned long pfn_base;
>   extern unsigned long kernel_virt_addr;
>   
>   #define linear_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_pa_offset))
> +#ifdef CONFIG_XIP_KERNEL
> +#define kernel_mapping_pa_to_va(y)	({						\
> +	unsigned long _y = y;								\
> +	(_y >= CONFIG_PHYS_RAM_BASE) ?							\
> +		(void *)((unsigned long)(_y) + va_kernel_pa_offset + XIP_OFFSET) :	\
> +		(void *)((unsigned long)(_y) + va_kernel_xip_pa_offset);		\
> +	})
> +#else
>   #define kernel_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_kernel_pa_offset))
> +#endif
>   #define __pa_to_va_nodebug(x)		linear_mapping_pa_to_va(x)
>   
>   #define linear_mapping_va_to_pa(x)	((unsigned long)(x) - va_pa_offset)
> +#ifdef CONFIG_XIP_KERNEL
> +#define kernel_mapping_va_to_pa(y) ({						\
> +	unsigned long _y = y;							\
> +	(_y < kernel_virt_addr + XIP_OFFSET) ?					\
> +		((unsigned long)(_y) - va_kernel_xip_pa_offset) :		\
> +		((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET);	\
> +	})
> +#else
>   #define kernel_mapping_va_to_pa(x)	((unsigned long)(x) - va_kernel_pa_offset)
> +#endif
>   #define __va_to_pa_nodebug(x)	({						\
>   	unsigned long _x = x;							\
>   	(_x < kernel_virt_addr) ?						\
> @@ -139,9 +160,16 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
>   #define phys_to_page(paddr)	(pfn_to_page(phys_to_pfn(paddr)))
>   
>   #ifdef CONFIG_FLATMEM
> +#ifdef CONFIG_XIP_KERNEL
> +#define pfn_valid(pfn) \
> +	((((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr)) ||	\
> +		((pfn) >= PFN_DOWN(CONFIG_XIP_PHYS_ADDR) &&				\
> +		(((pfn) - PFN_DOWN(CONFIG_XIP_PHYS_ADDR)) < XIP_OFFSET)))
> +#else
>   #define pfn_valid(pfn) \
>   	(((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr))
>   #endif
> +#endif
>   
>   #endif /* __ASSEMBLY__ */
>   
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 80e63a93e903..c2dc4f83eed8 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -64,6 +64,19 @@
>   #define FIXADDR_SIZE     PGDIR_SIZE
>   #endif
>   #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
> +
> +#ifdef CONFIG_XIP_KERNEL
> +#define XIP_OFFSET		SZ_8M
> +#define XIP_FIXUP(addr) ({							\
> +	uintptr_t __a = (uintptr_t)(addr);					\
> +	(__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR + SZ_16M) ?	\
> +		__a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - XIP_OFFSET :\
> +		__a;								\
> +	})
> +#else
> +#define XIP_FIXUP(addr)		(addr)
> +#endif /* CONFIG_XIP_KERNEL */
> +
>   #endif
>   
>   #ifndef __ASSEMBLY__
> @@ -499,8 +512,16 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
>   #define kern_addr_valid(addr)   (1) /* FIXME */
>   
>   extern char _start[];
> -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);
>   void misc_mem_init(void);
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 6cb05f22e52a..89cc58ab52b4 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -9,11 +9,23 @@
>   #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
> +	REG_L t0, _xip_fixup
> +	add \reg, \reg, t0
> +.endm
> +_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
> +#else
> +.macro XIP_FIXUP_OFFSET reg
> +.endm
> +#endif /* CONFIG_XIP_KERNEL */
> +
>   __HEAD
>   ENTRY(_start)
>   	/*
> @@ -70,6 +82,7 @@ pe_head_start:
>   relocate:
>   	/* Relocate return address */
>   	la a1, kernel_virt_addr
> +	XIP_FIXUP_OFFSET a1
>   	REG_L a1, 0(a1)
>   	la a2, _start
>   	sub a1, a1, a2
> @@ -92,6 +105,7 @@ relocate:
>   	 * to ensure the new translations are in use.
>   	 */
>   	la a0, trampoline_pg_dir
> +	XIP_FIXUP_OFFSET a0
>   	srl a0, a0, PAGE_SHIFT
>   	or a0, a0, a1
>   	sfence.vma
> @@ -145,7 +159,9 @@ secondary_start_sbi:
>   
>   	slli a3, a0, LGREG
>   	la a4, __cpu_up_stack_pointer
> +	XIP_FIXUP_OFFSET a4
>   	la a5, __cpu_up_task_pointer
> +	XIP_FIXUP_OFFSET a5
>   	add a4, a3, a4
>   	add a5, a3, a5
>   	REG_L sp, (a4)
> @@ -157,6 +173,7 @@ secondary_start_common:
>   #ifdef CONFIG_MMU
>   	/* Enable virtual memory and relocate to virtual address */
>   	la a0, swapper_pg_dir
> +	XIP_FIXUP_OFFSET a0
>   	call relocate
>   #endif
>   	call setup_trap_vector
> @@ -237,12 +254,33 @@ pmp_done:
>   .Lgood_cores:
>   #endif
>   
> +#ifndef CONFIG_XIP_KERNEL
>   	/* Pick one hart to run the main boot sequence */
>   	la a3, hart_lottery
>   	li a2, 1
>   	amoadd.w a3, a2, (a3)
>   	bnez a3, .Lsecondary_start
>   
> +#else
> +	/* hart_lottery in flash contains a magic number */
> +	la a3, hart_lottery
> +	mv a2, a3
> +	XIP_FIXUP_OFFSET a2
> +	lw t1, (a3)
> +	amoswap.w t0, t1, (a2)
> +	/* first time here if hart_lottery in RAM is not set */
> +	beq t0, t1, .Lsecondary_start
> +
> +	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
> @@ -252,15 +290,18 @@ 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
> +	XIP_FIXUP_OFFSET a2
>   	REG_S a0, (a2)
>   
>   	/* Initialize page tables and relocate to virtual addresses */
>   	la sp, init_thread_union + THREAD_SIZE
> +	XIP_FIXUP_OFFSET sp
>   #ifdef CONFIG_BUILTIN_DTB
>   	la a0, __dtb_start
>   #else
> @@ -269,6 +310,7 @@ clear_bss_done:
>   	call setup_vm
>   #ifdef CONFIG_MMU
>   	la a0, early_pg_dir
> +	XIP_FIXUP_OFFSET a0
>   	call relocate
>   #endif /* CONFIG_MMU */
>   
> @@ -293,7 +335,9 @@ clear_bss_done:
>   
>   	slli a3, a0, LGREG
>   	la a1, __cpu_up_stack_pointer
> +	XIP_FIXUP_OFFSET a1
>   	la a2, __cpu_up_task_pointer
> +	XIP_FIXUP_OFFSET a2
>   	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 30e4af0fd50c..2ddf654c72bb 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(0xC001BEEF)
> +#endif
> +;
>   unsigned long boot_cpu_hartid;
>   static DEFINE_PER_CPU(struct cpu, cpu_devices);
>   
> @@ -254,7 +258,7 @@ 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(__va(XIP_FIXUP(dtb_early_pa))))
>   		unflatten_device_tree();
>   	else
>   		pr_err("No DTB found in kernel mappings\n");
> @@ -266,7 +270,7 @@ void __init setup_arch(char **cmdline_p)
>   	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
>   		protect_kernel_text_data();
>   
> -#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)
> +#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL)
>   	protect_kernel_linear_mapping_text_rodata();
>   #endif
>   
> diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
> new file mode 100644
> index 000000000000..4b29b9917f99
> --- /dev/null
> +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
> @@ -0,0 +1,133 @@
> +/* 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
> + */
> +
> +#include <asm/pgtable.h>
> +#define LOAD_OFFSET KERNEL_LINK_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 */
> +	. = LOAD_OFFSET;
> +	_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 */
> +	. = LOAD_OFFSET + XIP_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 0726c05e0336..0a59b65cf789 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -4,8 +4,13 @@
>    * Copyright (C) 2017 SiFive
>    */
>   
> +#ifdef CONFIG_XIP_KERNEL
> +#include "vmlinux-xip.lds.S"
> +#else
> +
>   #include <asm/pgtable.h>
>   #define LOAD_OFFSET KERNEL_LINK_ADDR
> +
>   #include <asm/vmlinux.lds.h>
>   #include <asm/page.h>
>   #include <asm/cache.h>
> @@ -133,3 +138,4 @@ SECTIONS
>   
>   	DISCARDS
>   }
> +#endif /* CONFIG_XIP_KERNEL */
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 093f3a96ecfc..9961573f9a55 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -27,6 +27,9 @@
>   
>   unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
>   EXPORT_SYMBOL(kernel_virt_addr);
> +#ifdef CONFIG_XIP_KERNEL
> +#define kernel_virt_addr       (*((unsigned long *)XIP_FIXUP(&kernel_virt_addr)))
> +#endif
>   
>   unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>   							__page_aligned_bss;
> @@ -34,8 +37,8 @@ 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);
> @@ -118,6 +121,10 @@ void __init setup_bootmem(void)
>   	phys_addr_t dram_end = memblock_end_of_DRAM();
>   	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
>   
> +#ifdef CONFIG_XIP_KERNEL
> +	vmlinux_start = __pa_symbol(&_sdata);
> +#endif
> +
>   	/* The maximal physical memory size is -PAGE_OFFSET. */
>   	memblock_enforce_memory_limit(-PAGE_OFFSET);
>   
> @@ -159,17 +166,44 @@ void __init setup_bootmem(void)
>   	memblock_allow_resize();
>   }
>   
> +#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
>   
>   /* Offset between linear mapping virtual address and kernel load address */
>   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
>   /* Offset between kernel mapping virtual address and kernel load address */
>   unsigned long va_kernel_pa_offset;
>   EXPORT_SYMBOL(va_kernel_pa_offset);
> +#ifdef CONFIG_XIP_KERNEL
> +#define va_kernel_pa_offset    (*((unsigned long *)XIP_FIXUP(&va_kernel_pa_offset)))
> +#endif
> +unsigned long va_kernel_xip_pa_offset;
> +EXPORT_SYMBOL(va_kernel_xip_pa_offset);
> +#ifdef CONFIG_XIP_KERNEL
> +#define va_kernel_xip_pa_offset        (*((unsigned long *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
> +#endif
>   unsigned long pfn_base;
>   EXPORT_SYMBOL(pfn_base);
> +#ifdef CONFIG_XIP_KERNEL
> +#define pfn_base       (*((unsigned long *)XIP_FIXUP(&pfn_base)))
> +#endif
>   
>   pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>   pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
> @@ -177,6 +211,12 @@ pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>   
>   pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>   
> +#ifdef CONFIG_XIP_KERNEL
> +#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))
> +#endif /* CONFIG_XIP_KERNEL */
> +
>   void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>   {
>   	unsigned long addr = __fix_to_virt(idx);
> @@ -252,6 +292,12 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
>   pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>   pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>   
> +#ifdef CONFIG_XIP_KERNEL
> +#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
> +#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_pmd))
> +#define early_pmd      ((pmd_t *)XIP_FIXUP(early_pmd))
> +#endif /* CONFIG_XIP_KERNEL */
> +
>   static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
>   {
>   	/* Before MMU is enabled */
> @@ -368,6 +414,19 @@ 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_PHYS_RAM_BASE;
> +	size_t sz = (size_t)(end - from + 1);
> +
> +	memcpy(to, from, sz);
> +}
> +#endif
> +
>   /*
>    * setup_vm() is called from head.S with MMU-off.
>    *
> @@ -387,7 +446,35 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>   #endif
>   
>   uintptr_t load_pa, load_sz;
> +#ifdef CONFIG_XIP_KERNEL
> +#define load_pa        (*((uintptr_t *)XIP_FIXUP(&load_pa)))
> +#define load_sz        (*((uintptr_t *)XIP_FIXUP(&load_sz)))
> +#endif
> +
> +#ifdef CONFIG_XIP_KERNEL
> +uintptr_t xiprom, xiprom_sz;
> +#define xiprom_sz      (*((uintptr_t *)XIP_FIXUP(&xiprom_sz)))
> +#define xiprom         (*((uintptr_t *)XIP_FIXUP(&xiprom)))
>   
> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
> +{
> +	uintptr_t va, end_va;
> +
> +	/* Map the flash resident part */
> +	end_va = kernel_virt_addr + xiprom_sz;
> +	for (va = kernel_virt_addr; va < end_va; va += map_size)
> +		create_pgd_mapping(pgdir, va,
> +				   xiprom + (va - kernel_virt_addr),
> +				   map_size, PAGE_KERNEL_EXEC);
> +
> +	/* Map the data in RAM */
> +	end_va = kernel_virt_addr + XIP_OFFSET + load_sz;
> +	for (va = kernel_virt_addr + XIP_OFFSET; va < end_va; va += map_size)
> +		create_pgd_mapping(pgdir, va,
> +				   load_pa + (va - (kernel_virt_addr + XIP_OFFSET)),
> +				   map_size, PAGE_KERNEL);
> +}
> +#else
>   static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>   {
>   	uintptr_t va, end_va;
> @@ -398,16 +485,28 @@ static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>   				   load_pa + (va - kernel_virt_addr),
>   				   map_size, PAGE_KERNEL_EXEC);
>   }
> +#endif
>   
>   asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   {
> -	uintptr_t pa;
> +	uintptr_t __maybe_unused pa;
>   	uintptr_t map_size;
>   #ifndef __PAGETABLE_PMD_FOLDED
>   	pmd_t fix_bmap_spmd, fix_bmap_epmd;
>   #endif
> +
> +#ifdef CONFIG_XIP_KERNEL
> +	xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
> +	xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
> +
> +	load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
> +	load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
> +
> +	va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
> +#else
>   	load_pa = (uintptr_t)(&_start);
>   	load_sz = (uintptr_t)(&_end) - load_pa;
> +#endif
>   
>   	va_pa_offset = PAGE_OFFSET - load_pa;
>   	va_kernel_pa_offset = kernel_virt_addr - load_pa;
> @@ -441,8 +540,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   	/* Setup trampoline PGD and PMD */
>   	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>   			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
> +#ifdef CONFIG_XIP_KERNEL
> +	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
> +			   xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
> +#else
>   	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>   			   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
> +#endif
>   #else
>   	/* Setup trampoline PGD */
>   	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
> @@ -474,7 +578,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   	 * whereas dtb_early_va will be used before setup_vm_final installs
>   	 * the linear mapping.
>   	 */
> -	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
> +	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>   #endif /* CONFIG_BUILTIN_DTB */
>   #else
>   #ifndef CONFIG_BUILTIN_DTB
> @@ -486,7 +590,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   			   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
>   	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
>   #else /* CONFIG_BUILTIN_DTB */
> -	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
> +	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>   #endif /* CONFIG_BUILTIN_DTB */
>   #endif
>   	dtb_early_pa = dtb_pa;
> @@ -522,7 +626,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>   #endif
>   }
>   
> -#ifdef CONFIG_64BIT
> +#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
>   void protect_kernel_linear_mapping_text_rodata(void)
>   {
>   	unsigned long text_start = (unsigned long)lm_alias(_start);
>
David Hildenbrand April 9, 2021, 8:23 a.m. UTC | #2
On 09.04.21 09:14, Alex Ghiti wrote:
> Le 4/9/21 à 2:51 AM, Alexandre Ghiti a écrit :
>> From: Vitaly Wool <vitaly.wool@konsulko.com>
>>
>> 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. 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 for the time being only work on MMU-enabled
>> kernels.
>>
> I added linux-mm and linux-arch to get feedbacks because I noticed that
> DEBUG_VM_PGTABLE fails for SPARSEMEM (it works for FLATMEM but I think
> it does not do what is expected): the fact that we don't have any struct
> page to back the text and rodata in flash is the problem but to which
> extent ?

Just wondering, why can't we create a memmap for that memory -- or is it 
even desireable to not do that explicity? There might be some nasty side 
effects when not having a memmap for text and rodata.

I would assume stimply exposing the physical memory range to memblock as 
RAM and marking it reserved would create a memmap that's fully 
initialized like any bootmem (PG_reserved).

Or is there a reason why we cannot do that?

Also, will that memory properly be exposed in the resource tree as 
System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore) 
won't work as expected - the kernel won't be included in a dump.


> 
> Thanks,
> 
> Alex
> 
>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> [ Rebase on top of "Move
>> kernel mapping outside the linear mapping ]
>> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
>> ---
>>
>> Changes 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.
>> Changes in v3:
>> - rebased against latest for-next
>> - XIP address fixup macro now takes an argument
>> - SMP related fixes
>> Changes in v4:
>> - rebased against the current for-next
>> - less #ifdef's in C/ASM code
>> - dedicated XIP_FIXUP_OFFSET assembler macro in head.S
>> - C-specific definitions moved into #ifndef __ASSEMBLY__
>> - Fixed multi-core boot
>> Changes in v5:
>> - fixed build error for non-XIP kernels
>> Changes in v6:
>> - XIP_PHYS_RAM_BASE config option renamed to PHYS_RAM_BASE
>> - added PHYS_RAM_BASE_FIXED config flag to allow usage of
>>     PHYS_RAM_BASE in non-XIP configurations if needed
>> - XIP_FIXUP macro rewritten with a tempoarary variable to avoid side
>>     effects
>> - fixed crash for non-XIP kernels that don't use built-in DTB
>> Changes in v7:
>> - Fix pfn_base that required FIXUP
>> - Fix copy_data which lacked + 1 in size to copy
>> - Fix pfn_valid for FLATMEM
>> - Rebased on top of "Move kernel mapping outside the linear mapping":
>>     this is the biggest change and affected mm/init.c,
>>     kernel/vmlinux-xip.lds.S and include/asm/pgtable.h: XIP kernel is now
>>     mapped like 'normal' kernel at the end of the address space.
>>
>>    arch/riscv/Kconfig                  |  51 ++++++++++-
>>    arch/riscv/Makefile                 |   8 +-
>>    arch/riscv/boot/Makefile            |  13 +++
>>    arch/riscv/include/asm/page.h       |  28 ++++++
>>    arch/riscv/include/asm/pgtable.h    |  25 +++++-
>>    arch/riscv/kernel/head.S            |  46 +++++++++-
>>    arch/riscv/kernel/head.h            |   3 +
>>    arch/riscv/kernel/setup.c           |  10 ++-
>>    arch/riscv/kernel/vmlinux-xip.lds.S | 133 ++++++++++++++++++++++++++++
>>    arch/riscv/kernel/vmlinux.lds.S     |   6 ++
>>    arch/riscv/mm/init.c                | 118 ++++++++++++++++++++++--
>>    11 files changed, 424 insertions(+), 17 deletions(-)
>>    create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 8ea60a0a19ae..4d0153805927 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -28,7 +28,7 @@ config RISCV
>>    	select ARCH_HAS_PTE_SPECIAL
>>    	select ARCH_HAS_SET_DIRECT_MAP
>>    	select ARCH_HAS_SET_MEMORY
>> -	select ARCH_HAS_STRICT_KERNEL_RWX if MMU
>> +	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>>    	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>>    	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>>    	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>> @@ -441,7 +441,7 @@ 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
>> @@ -465,11 +465,56 @@ config STACKPROTECTOR_PER_TASK
>>    	def_bool y
>>    	depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
>>    
>> +config PHYS_RAM_BASE_FIXED
>> +	bool "Explicitly specified physical RAM address"
>> +	default n
>> +
>> +config PHYS_RAM_BASE
>> +	hex "Platform Physical RAM address"
>> +	depends on PHYS_RAM_BASE_FIXED
>> +	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.
>> +
>> +config XIP_KERNEL
>> +	bool "Kernel Execute-In-Place from ROM"
>> +	depends on MMU
>> +	select PHYS_RAM_BASE_FIXED
>> +	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.
>> +
>>    endmenu
>>    
>>    config BUILTIN_DTB
>> -	def_bool n
>> +	bool
>>    	depends on OF
>> +	default y if XIP_KERNEL
>>    
>>    menu "Power management options"
>>    
>> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
>> index 1368d943f1f3..8fcbec03974d 100644
>> --- a/arch/riscv/Makefile
>> +++ b/arch/riscv/Makefile
>> @@ -82,7 +82,11 @@ 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
>>    
>> @@ -95,12 +99,14 @@ PHONY += vdso_install
>>    vdso_install:
>>    	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
>>    
>> +ifneq ($(CONFIG_XIP_KERNEL),y)
>>    ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),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/page.h b/arch/riscv/include/asm/page.h
>> index 22cfb2be60dc..6fe0ff8c8fa9 100644
>> --- a/arch/riscv/include/asm/page.h
>> +++ b/arch/riscv/include/asm/page.h
>> @@ -91,6 +91,9 @@ typedef struct page *pgtable_t;
>>    #ifdef CONFIG_MMU
>>    extern unsigned long va_pa_offset;
>>    extern unsigned long va_kernel_pa_offset;
>> +#ifdef CONFIG_XIP_KERNEL
>> +extern unsigned long va_kernel_xip_pa_offset;
>> +#endif
>>    extern unsigned long pfn_base;
>>    #define ARCH_PFN_OFFSET		(pfn_base)
>>    #else
>> @@ -102,11 +105,29 @@ extern unsigned long pfn_base;
>>    extern unsigned long kernel_virt_addr;
>>    
>>    #define linear_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_pa_offset))
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define kernel_mapping_pa_to_va(y)	({						\
>> +	unsigned long _y = y;								\
>> +	(_y >= CONFIG_PHYS_RAM_BASE) ?							\
>> +		(void *)((unsigned long)(_y) + va_kernel_pa_offset + XIP_OFFSET) :	\
>> +		(void *)((unsigned long)(_y) + va_kernel_xip_pa_offset);		\
>> +	})
>> +#else
>>    #define kernel_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_kernel_pa_offset))
>> +#endif
>>    #define __pa_to_va_nodebug(x)		linear_mapping_pa_to_va(x)
>>    
>>    #define linear_mapping_va_to_pa(x)	((unsigned long)(x) - va_pa_offset)
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define kernel_mapping_va_to_pa(y) ({						\
>> +	unsigned long _y = y;							\
>> +	(_y < kernel_virt_addr + XIP_OFFSET) ?					\
>> +		((unsigned long)(_y) - va_kernel_xip_pa_offset) :		\
>> +		((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET);	\
>> +	})
>> +#else
>>    #define kernel_mapping_va_to_pa(x)	((unsigned long)(x) - va_kernel_pa_offset)
>> +#endif
>>    #define __va_to_pa_nodebug(x)	({						\
>>    	unsigned long _x = x;							\
>>    	(_x < kernel_virt_addr) ?						\
>> @@ -139,9 +160,16 @@ extern phys_addr_t __phys_addr_symbol(unsigned long x);
>>    #define phys_to_page(paddr)	(pfn_to_page(phys_to_pfn(paddr)))
>>    
>>    #ifdef CONFIG_FLATMEM
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define pfn_valid(pfn) \
>> +	((((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr)) ||	\
>> +		((pfn) >= PFN_DOWN(CONFIG_XIP_PHYS_ADDR) &&				\
>> +		(((pfn) - PFN_DOWN(CONFIG_XIP_PHYS_ADDR)) < XIP_OFFSET)))
>> +#else
>>    #define pfn_valid(pfn) \
>>    	(((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr))
>>    #endif
>> +#endif
>>    
>>    #endif /* __ASSEMBLY__ */
>>    
>> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
>> index 80e63a93e903..c2dc4f83eed8 100644
>> --- a/arch/riscv/include/asm/pgtable.h
>> +++ b/arch/riscv/include/asm/pgtable.h
>> @@ -64,6 +64,19 @@
>>    #define FIXADDR_SIZE     PGDIR_SIZE
>>    #endif
>>    #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
>> +
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define XIP_OFFSET		SZ_8M
>> +#define XIP_FIXUP(addr) ({							\
>> +	uintptr_t __a = (uintptr_t)(addr);					\
>> +	(__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR + SZ_16M) ?	\
>> +		__a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - XIP_OFFSET :\
>> +		__a;								\
>> +	})
>> +#else
>> +#define XIP_FIXUP(addr)		(addr)
>> +#endif /* CONFIG_XIP_KERNEL */
>> +
>>    #endif
>>    
>>    #ifndef __ASSEMBLY__
>> @@ -499,8 +512,16 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
>>    #define kern_addr_valid(addr)   (1) /* FIXME */
>>    
>>    extern char _start[];
>> -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);
>>    void misc_mem_init(void);
>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>> index 6cb05f22e52a..89cc58ab52b4 100644
>> --- a/arch/riscv/kernel/head.S
>> +++ b/arch/riscv/kernel/head.S
>> @@ -9,11 +9,23 @@
>>    #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
>> +	REG_L t0, _xip_fixup
>> +	add \reg, \reg, t0
>> +.endm
>> +_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
>> +#else
>> +.macro XIP_FIXUP_OFFSET reg
>> +.endm
>> +#endif /* CONFIG_XIP_KERNEL */
>> +
>>    __HEAD
>>    ENTRY(_start)
>>    	/*
>> @@ -70,6 +82,7 @@ pe_head_start:
>>    relocate:
>>    	/* Relocate return address */
>>    	la a1, kernel_virt_addr
>> +	XIP_FIXUP_OFFSET a1
>>    	REG_L a1, 0(a1)
>>    	la a2, _start
>>    	sub a1, a1, a2
>> @@ -92,6 +105,7 @@ relocate:
>>    	 * to ensure the new translations are in use.
>>    	 */
>>    	la a0, trampoline_pg_dir
>> +	XIP_FIXUP_OFFSET a0
>>    	srl a0, a0, PAGE_SHIFT
>>    	or a0, a0, a1
>>    	sfence.vma
>> @@ -145,7 +159,9 @@ secondary_start_sbi:
>>    
>>    	slli a3, a0, LGREG
>>    	la a4, __cpu_up_stack_pointer
>> +	XIP_FIXUP_OFFSET a4
>>    	la a5, __cpu_up_task_pointer
>> +	XIP_FIXUP_OFFSET a5
>>    	add a4, a3, a4
>>    	add a5, a3, a5
>>    	REG_L sp, (a4)
>> @@ -157,6 +173,7 @@ secondary_start_common:
>>    #ifdef CONFIG_MMU
>>    	/* Enable virtual memory and relocate to virtual address */
>>    	la a0, swapper_pg_dir
>> +	XIP_FIXUP_OFFSET a0
>>    	call relocate
>>    #endif
>>    	call setup_trap_vector
>> @@ -237,12 +254,33 @@ pmp_done:
>>    .Lgood_cores:
>>    #endif
>>    
>> +#ifndef CONFIG_XIP_KERNEL
>>    	/* Pick one hart to run the main boot sequence */
>>    	la a3, hart_lottery
>>    	li a2, 1
>>    	amoadd.w a3, a2, (a3)
>>    	bnez a3, .Lsecondary_start
>>    
>> +#else
>> +	/* hart_lottery in flash contains a magic number */
>> +	la a3, hart_lottery
>> +	mv a2, a3
>> +	XIP_FIXUP_OFFSET a2
>> +	lw t1, (a3)
>> +	amoswap.w t0, t1, (a2)
>> +	/* first time here if hart_lottery in RAM is not set */
>> +	beq t0, t1, .Lsecondary_start
>> +
>> +	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
>> @@ -252,15 +290,18 @@ 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
>> +	XIP_FIXUP_OFFSET a2
>>    	REG_S a0, (a2)
>>    
>>    	/* Initialize page tables and relocate to virtual addresses */
>>    	la sp, init_thread_union + THREAD_SIZE
>> +	XIP_FIXUP_OFFSET sp
>>    #ifdef CONFIG_BUILTIN_DTB
>>    	la a0, __dtb_start
>>    #else
>> @@ -269,6 +310,7 @@ clear_bss_done:
>>    	call setup_vm
>>    #ifdef CONFIG_MMU
>>    	la a0, early_pg_dir
>> +	XIP_FIXUP_OFFSET a0
>>    	call relocate
>>    #endif /* CONFIG_MMU */
>>    
>> @@ -293,7 +335,9 @@ clear_bss_done:
>>    
>>    	slli a3, a0, LGREG
>>    	la a1, __cpu_up_stack_pointer
>> +	XIP_FIXUP_OFFSET a1
>>    	la a2, __cpu_up_task_pointer
>> +	XIP_FIXUP_OFFSET a2
>>    	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 30e4af0fd50c..2ddf654c72bb 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(0xC001BEEF)
>> +#endif
>> +;
>>    unsigned long boot_cpu_hartid;
>>    static DEFINE_PER_CPU(struct cpu, cpu_devices);
>>    
>> @@ -254,7 +258,7 @@ 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(__va(XIP_FIXUP(dtb_early_pa))))
>>    		unflatten_device_tree();
>>    	else
>>    		pr_err("No DTB found in kernel mappings\n");
>> @@ -266,7 +270,7 @@ void __init setup_arch(char **cmdline_p)
>>    	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
>>    		protect_kernel_text_data();
>>    
>> -#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)
>> +#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL)
>>    	protect_kernel_linear_mapping_text_rodata();
>>    #endif
>>    
>> diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
>> new file mode 100644
>> index 000000000000..4b29b9917f99
>> --- /dev/null
>> +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
>> @@ -0,0 +1,133 @@
>> +/* 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
>> + */
>> +
>> +#include <asm/pgtable.h>
>> +#define LOAD_OFFSET KERNEL_LINK_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 */
>> +	. = LOAD_OFFSET;
>> +	_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 */
>> +	. = LOAD_OFFSET + XIP_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 0726c05e0336..0a59b65cf789 100644
>> --- a/arch/riscv/kernel/vmlinux.lds.S
>> +++ b/arch/riscv/kernel/vmlinux.lds.S
>> @@ -4,8 +4,13 @@
>>     * Copyright (C) 2017 SiFive
>>     */
>>    
>> +#ifdef CONFIG_XIP_KERNEL
>> +#include "vmlinux-xip.lds.S"
>> +#else
>> +
>>    #include <asm/pgtable.h>
>>    #define LOAD_OFFSET KERNEL_LINK_ADDR
>> +
>>    #include <asm/vmlinux.lds.h>
>>    #include <asm/page.h>
>>    #include <asm/cache.h>
>> @@ -133,3 +138,4 @@ SECTIONS
>>    
>>    	DISCARDS
>>    }
>> +#endif /* CONFIG_XIP_KERNEL */
>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>> index 093f3a96ecfc..9961573f9a55 100644
>> --- a/arch/riscv/mm/init.c
>> +++ b/arch/riscv/mm/init.c
>> @@ -27,6 +27,9 @@
>>    
>>    unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
>>    EXPORT_SYMBOL(kernel_virt_addr);
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define kernel_virt_addr       (*((unsigned long *)XIP_FIXUP(&kernel_virt_addr)))
>> +#endif
>>    
>>    unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>>    							__page_aligned_bss;
>> @@ -34,8 +37,8 @@ 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);
>> @@ -118,6 +121,10 @@ void __init setup_bootmem(void)
>>    	phys_addr_t dram_end = memblock_end_of_DRAM();
>>    	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
>>    
>> +#ifdef CONFIG_XIP_KERNEL
>> +	vmlinux_start = __pa_symbol(&_sdata);
>> +#endif
>> +
>>    	/* The maximal physical memory size is -PAGE_OFFSET. */
>>    	memblock_enforce_memory_limit(-PAGE_OFFSET);
>>    
>> @@ -159,17 +166,44 @@ void __init setup_bootmem(void)
>>    	memblock_allow_resize();
>>    }
>>    
>> +#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
>>    
>>    /* Offset between linear mapping virtual address and kernel load address */
>>    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
>>    /* Offset between kernel mapping virtual address and kernel load address */
>>    unsigned long va_kernel_pa_offset;
>>    EXPORT_SYMBOL(va_kernel_pa_offset);
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define va_kernel_pa_offset    (*((unsigned long *)XIP_FIXUP(&va_kernel_pa_offset)))
>> +#endif
>> +unsigned long va_kernel_xip_pa_offset;
>> +EXPORT_SYMBOL(va_kernel_xip_pa_offset);
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define va_kernel_xip_pa_offset        (*((unsigned long *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
>> +#endif
>>    unsigned long pfn_base;
>>    EXPORT_SYMBOL(pfn_base);
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define pfn_base       (*((unsigned long *)XIP_FIXUP(&pfn_base)))
>> +#endif
>>    
>>    pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>>    pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>> @@ -177,6 +211,12 @@ pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>>    
>>    pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>>    
>> +#ifdef CONFIG_XIP_KERNEL
>> +#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))
>> +#endif /* CONFIG_XIP_KERNEL */
>> +
>>    void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
>>    {
>>    	unsigned long addr = __fix_to_virt(idx);
>> @@ -252,6 +292,12 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
>>    pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>    pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>    
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
>> +#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_pmd))
>> +#define early_pmd      ((pmd_t *)XIP_FIXUP(early_pmd))
>> +#endif /* CONFIG_XIP_KERNEL */
>> +
>>    static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
>>    {
>>    	/* Before MMU is enabled */
>> @@ -368,6 +414,19 @@ 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_PHYS_RAM_BASE;
>> +	size_t sz = (size_t)(end - from + 1);
>> +
>> +	memcpy(to, from, sz);
>> +}
>> +#endif
>> +
>>    /*
>>     * setup_vm() is called from head.S with MMU-off.
>>     *
>> @@ -387,7 +446,35 @@ static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
>>    #endif
>>    
>>    uintptr_t load_pa, load_sz;
>> +#ifdef CONFIG_XIP_KERNEL
>> +#define load_pa        (*((uintptr_t *)XIP_FIXUP(&load_pa)))
>> +#define load_sz        (*((uintptr_t *)XIP_FIXUP(&load_sz)))
>> +#endif
>> +
>> +#ifdef CONFIG_XIP_KERNEL
>> +uintptr_t xiprom, xiprom_sz;
>> +#define xiprom_sz      (*((uintptr_t *)XIP_FIXUP(&xiprom_sz)))
>> +#define xiprom         (*((uintptr_t *)XIP_FIXUP(&xiprom)))
>>    
>> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>> +{
>> +	uintptr_t va, end_va;
>> +
>> +	/* Map the flash resident part */
>> +	end_va = kernel_virt_addr + xiprom_sz;
>> +	for (va = kernel_virt_addr; va < end_va; va += map_size)
>> +		create_pgd_mapping(pgdir, va,
>> +				   xiprom + (va - kernel_virt_addr),
>> +				   map_size, PAGE_KERNEL_EXEC);
>> +
>> +	/* Map the data in RAM */
>> +	end_va = kernel_virt_addr + XIP_OFFSET + load_sz;
>> +	for (va = kernel_virt_addr + XIP_OFFSET; va < end_va; va += map_size)
>> +		create_pgd_mapping(pgdir, va,
>> +				   load_pa + (va - (kernel_virt_addr + XIP_OFFSET)),
>> +				   map_size, PAGE_KERNEL);
>> +}
>> +#else
>>    static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>>    {
>>    	uintptr_t va, end_va;
>> @@ -398,16 +485,28 @@ static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>>    				   load_pa + (va - kernel_virt_addr),
>>    				   map_size, PAGE_KERNEL_EXEC);
>>    }
>> +#endif
>>    
>>    asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>    {
>> -	uintptr_t pa;
>> +	uintptr_t __maybe_unused pa;
>>    	uintptr_t map_size;
>>    #ifndef __PAGETABLE_PMD_FOLDED
>>    	pmd_t fix_bmap_spmd, fix_bmap_epmd;
>>    #endif
>> +
>> +#ifdef CONFIG_XIP_KERNEL
>> +	xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
>> +	xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
>> +
>> +	load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
>> +	load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
>> +
>> +	va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
>> +#else
>>    	load_pa = (uintptr_t)(&_start);
>>    	load_sz = (uintptr_t)(&_end) - load_pa;
>> +#endif
>>    
>>    	va_pa_offset = PAGE_OFFSET - load_pa;
>>    	va_kernel_pa_offset = kernel_virt_addr - load_pa;
>> @@ -441,8 +540,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>    	/* Setup trampoline PGD and PMD */
>>    	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>    			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
>> +#ifdef CONFIG_XIP_KERNEL
>> +	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>> +			   xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
>> +#else
>>    	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>>    			   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>> +#endif
>>    #else
>>    	/* Setup trampoline PGD */
>>    	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>> @@ -474,7 +578,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>    	 * whereas dtb_early_va will be used before setup_vm_final installs
>>    	 * the linear mapping.
>>    	 */
>> -	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
>> +	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>>    #endif /* CONFIG_BUILTIN_DTB */
>>    #else
>>    #ifndef CONFIG_BUILTIN_DTB
>> @@ -486,7 +590,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>    			   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
>>    	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
>>    #else /* CONFIG_BUILTIN_DTB */
>> -	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
>> +	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>>    #endif /* CONFIG_BUILTIN_DTB */
>>    #endif
>>    	dtb_early_pa = dtb_pa;
>> @@ -522,7 +626,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>    #endif
>>    }
>>    
>> -#ifdef CONFIG_64BIT
>> +#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
>>    void protect_kernel_linear_mapping_text_rodata(void)
>>    {
>>    	unsigned long text_start = (unsigned long)lm_alias(_start);
>>
>
Alex Ghiti April 9, 2021, 11:39 a.m. UTC | #3
Hi David,

Le 4/9/21 à 4:23 AM, David Hildenbrand a écrit :
> On 09.04.21 09:14, Alex Ghiti wrote:
>> Le 4/9/21 à 2:51 AM, Alexandre Ghiti a écrit :
>>> From: Vitaly Wool <vitaly.wool@konsulko.com>
>>>
>>> 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. 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 for the time being only work on MMU-enabled
>>> kernels.
>>>
>> I added linux-mm and linux-arch to get feedbacks because I noticed that
>> DEBUG_VM_PGTABLE fails for SPARSEMEM (it works for FLATMEM but I think
>> it does not do what is expected): the fact that we don't have any struct
>> page to back the text and rodata in flash is the problem but to which
>> extent ?
> 
> Just wondering, why can't we create a memmap for that memory -- or is it 
> even desireable to not do that explicity? There might be some nasty side 
> effects when not having a memmap for text and rodata.


Do you have examples of such effects ? Any feature that will not work 
without that ?


> 
> I would assume stimply exposing the physical memory range to memblock as 
> RAM and marking it reserved would create a memmap that's fully 
> initialized like any bootmem (PG_reserved).
> 
> Or is there a reason why we cannot do that?


I did not want to do that if it was not needed as the overall goal of 
XIP kernel is to save RAM (I may be cheap but 16MB backed by struct page 
represents ~220KB).



> 
> Also, will that memory properly be exposed in the resource tree as 
> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore) 
> won't work as expected - the kernel won't be included in a dump.


I have just checked and it does not appear in /proc/iomem.

Ok your conclusion would be to have struct page, I'm going to implement 
this version then using memblock as you described.

Thanks David,

Alex

> 
> 
>>
>> Thanks,
>>
>> Alex
>>
>>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> [ Rebase on top of "Move
>>> kernel mapping outside the linear mapping ]
>>> Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
>>> ---
>>>
>>> Changes 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.
>>> Changes in v3:
>>> - rebased against latest for-next
>>> - XIP address fixup macro now takes an argument
>>> - SMP related fixes
>>> Changes in v4:
>>> - rebased against the current for-next
>>> - less #ifdef's in C/ASM code
>>> - dedicated XIP_FIXUP_OFFSET assembler macro in head.S
>>> - C-specific definitions moved into #ifndef __ASSEMBLY__
>>> - Fixed multi-core boot
>>> Changes in v5:
>>> - fixed build error for non-XIP kernels
>>> Changes in v6:
>>> - XIP_PHYS_RAM_BASE config option renamed to PHYS_RAM_BASE
>>> - added PHYS_RAM_BASE_FIXED config flag to allow usage of
>>>     PHYS_RAM_BASE in non-XIP configurations if needed
>>> - XIP_FIXUP macro rewritten with a tempoarary variable to avoid side
>>>     effects
>>> - fixed crash for non-XIP kernels that don't use built-in DTB
>>> Changes in v7:
>>> - Fix pfn_base that required FIXUP
>>> - Fix copy_data which lacked + 1 in size to copy
>>> - Fix pfn_valid for FLATMEM
>>> - Rebased on top of "Move kernel mapping outside the linear mapping":
>>>     this is the biggest change and affected mm/init.c,
>>>     kernel/vmlinux-xip.lds.S and include/asm/pgtable.h: XIP kernel is 
>>> now
>>>     mapped like 'normal' kernel at the end of the address space.
>>>
>>>    arch/riscv/Kconfig                  |  51 ++++++++++-
>>>    arch/riscv/Makefile                 |   8 +-
>>>    arch/riscv/boot/Makefile            |  13 +++
>>>    arch/riscv/include/asm/page.h       |  28 ++++++
>>>    arch/riscv/include/asm/pgtable.h    |  25 +++++-
>>>    arch/riscv/kernel/head.S            |  46 +++++++++-
>>>    arch/riscv/kernel/head.h            |   3 +
>>>    arch/riscv/kernel/setup.c           |  10 ++-
>>>    arch/riscv/kernel/vmlinux-xip.lds.S | 133 
>>> ++++++++++++++++++++++++++++
>>>    arch/riscv/kernel/vmlinux.lds.S     |   6 ++
>>>    arch/riscv/mm/init.c                | 118 ++++++++++++++++++++++--
>>>    11 files changed, 424 insertions(+), 17 deletions(-)
>>>    create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
>>>
>>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>>> index 8ea60a0a19ae..4d0153805927 100644
>>> --- a/arch/riscv/Kconfig
>>> +++ b/arch/riscv/Kconfig
>>> @@ -28,7 +28,7 @@ config RISCV
>>>        select ARCH_HAS_PTE_SPECIAL
>>>        select ARCH_HAS_SET_DIRECT_MAP
>>>        select ARCH_HAS_SET_MEMORY
>>> -    select ARCH_HAS_STRICT_KERNEL_RWX if MMU
>>> +    select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
>>>        select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
>>>        select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
>>>        select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
>>> @@ -441,7 +441,7 @@ 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
>>> @@ -465,11 +465,56 @@ config STACKPROTECTOR_PER_TASK
>>>        def_bool y
>>>        depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
>>> +config PHYS_RAM_BASE_FIXED
>>> +    bool "Explicitly specified physical RAM address"
>>> +    default n
>>> +
>>> +config PHYS_RAM_BASE
>>> +    hex "Platform Physical RAM address"
>>> +    depends on PHYS_RAM_BASE_FIXED
>>> +    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.
>>> +
>>> +config XIP_KERNEL
>>> +    bool "Kernel Execute-In-Place from ROM"
>>> +    depends on MMU
>>> +    select PHYS_RAM_BASE_FIXED
>>> +    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.
>>> +
>>>    endmenu
>>>    config BUILTIN_DTB
>>> -    def_bool n
>>> +    bool
>>>        depends on OF
>>> +    default y if XIP_KERNEL
>>>    menu "Power management options"
>>> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
>>> index 1368d943f1f3..8fcbec03974d 100644
>>> --- a/arch/riscv/Makefile
>>> +++ b/arch/riscv/Makefile
>>> @@ -82,7 +82,11 @@ 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
>>> @@ -95,12 +99,14 @@ PHONY += vdso_install
>>>    vdso_install:
>>>        $(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
>>> +ifneq ($(CONFIG_XIP_KERNEL),y)
>>>    ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),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/page.h 
>>> b/arch/riscv/include/asm/page.h
>>> index 22cfb2be60dc..6fe0ff8c8fa9 100644
>>> --- a/arch/riscv/include/asm/page.h
>>> +++ b/arch/riscv/include/asm/page.h
>>> @@ -91,6 +91,9 @@ typedef struct page *pgtable_t;
>>>    #ifdef CONFIG_MMU
>>>    extern unsigned long va_pa_offset;
>>>    extern unsigned long va_kernel_pa_offset;
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +extern unsigned long va_kernel_xip_pa_offset;
>>> +#endif
>>>    extern unsigned long pfn_base;
>>>    #define ARCH_PFN_OFFSET        (pfn_base)
>>>    #else
>>> @@ -102,11 +105,29 @@ extern unsigned long pfn_base;
>>>    extern unsigned long kernel_virt_addr;
>>>    #define linear_mapping_pa_to_va(x)    ((void *)((unsigned long)(x) 
>>> + va_pa_offset))
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define kernel_mapping_pa_to_va(y)    ({                        \
>>> +    unsigned long _y = y;                                \
>>> +    (_y >= CONFIG_PHYS_RAM_BASE) ?                            \
>>> +        (void *)((unsigned long)(_y) + va_kernel_pa_offset + 
>>> XIP_OFFSET) :    \
>>> +        (void *)((unsigned long)(_y) + 
>>> va_kernel_xip_pa_offset);        \
>>> +    })
>>> +#else
>>>    #define kernel_mapping_pa_to_va(x)    ((void *)((unsigned long)(x) 
>>> + va_kernel_pa_offset))
>>> +#endif
>>>    #define __pa_to_va_nodebug(x)        linear_mapping_pa_to_va(x)
>>>    #define linear_mapping_va_to_pa(x)    ((unsigned long)(x) - 
>>> va_pa_offset)
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define kernel_mapping_va_to_pa(y) ({                        \
>>> +    unsigned long _y = y;                            \
>>> +    (_y < kernel_virt_addr + XIP_OFFSET) ?                    \
>>> +        ((unsigned long)(_y) - va_kernel_xip_pa_offset) :        \
>>> +        ((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET);    \
>>> +    })
>>> +#else
>>>    #define kernel_mapping_va_to_pa(x)    ((unsigned long)(x) - 
>>> va_kernel_pa_offset)
>>> +#endif
>>>    #define __va_to_pa_nodebug(x)    ({                        \
>>>        unsigned long _x = x;                            \
>>>        (_x < kernel_virt_addr) ?                        \
>>> @@ -139,9 +160,16 @@ extern phys_addr_t __phys_addr_symbol(unsigned 
>>> long x);
>>>    #define phys_to_page(paddr)    (pfn_to_page(phys_to_pfn(paddr)))
>>>    #ifdef CONFIG_FLATMEM
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define pfn_valid(pfn) \
>>> +    ((((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < 
>>> max_mapnr)) ||    \
>>> +        ((pfn) >= PFN_DOWN(CONFIG_XIP_PHYS_ADDR) &&                \
>>> +        (((pfn) - PFN_DOWN(CONFIG_XIP_PHYS_ADDR)) < XIP_OFFSET)))
>>> +#else
>>>    #define pfn_valid(pfn) \
>>>        (((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < 
>>> max_mapnr))
>>>    #endif
>>> +#endif
>>>    #endif /* __ASSEMBLY__ */
>>> diff --git a/arch/riscv/include/asm/pgtable.h 
>>> b/arch/riscv/include/asm/pgtable.h
>>> index 80e63a93e903..c2dc4f83eed8 100644
>>> --- a/arch/riscv/include/asm/pgtable.h
>>> +++ b/arch/riscv/include/asm/pgtable.h
>>> @@ -64,6 +64,19 @@
>>>    #define FIXADDR_SIZE     PGDIR_SIZE
>>>    #endif
>>>    #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
>>> +
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define XIP_OFFSET        SZ_8M
>>> +#define XIP_FIXUP(addr) ({                            \
>>> +    uintptr_t __a = (uintptr_t)(addr);                    \
>>> +    (__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR + 
>>> SZ_16M) ?    \
>>> +        __a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - 
>>> XIP_OFFSET :\
>>> +        __a;                                \
>>> +    })
>>> +#else
>>> +#define XIP_FIXUP(addr)        (addr)
>>> +#endif /* CONFIG_XIP_KERNEL */
>>> +
>>>    #endif
>>>    #ifndef __ASSEMBLY__
>>> @@ -499,8 +512,16 @@ static inline int ptep_clear_flush_young(struct 
>>> vm_area_struct *vma,
>>>    #define kern_addr_valid(addr)   (1) /* FIXME */
>>>    extern char _start[];
>>> -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);
>>>    void misc_mem_init(void);
>>> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
>>> index 6cb05f22e52a..89cc58ab52b4 100644
>>> --- a/arch/riscv/kernel/head.S
>>> +++ b/arch/riscv/kernel/head.S
>>> @@ -9,11 +9,23 @@
>>>    #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
>>> +    REG_L t0, _xip_fixup
>>> +    add \reg, \reg, t0
>>> +.endm
>>> +_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - 
>>> XIP_OFFSET
>>> +#else
>>> +.macro XIP_FIXUP_OFFSET reg
>>> +.endm
>>> +#endif /* CONFIG_XIP_KERNEL */
>>> +
>>>    __HEAD
>>>    ENTRY(_start)
>>>        /*
>>> @@ -70,6 +82,7 @@ pe_head_start:
>>>    relocate:
>>>        /* Relocate return address */
>>>        la a1, kernel_virt_addr
>>> +    XIP_FIXUP_OFFSET a1
>>>        REG_L a1, 0(a1)
>>>        la a2, _start
>>>        sub a1, a1, a2
>>> @@ -92,6 +105,7 @@ relocate:
>>>         * to ensure the new translations are in use.
>>>         */
>>>        la a0, trampoline_pg_dir
>>> +    XIP_FIXUP_OFFSET a0
>>>        srl a0, a0, PAGE_SHIFT
>>>        or a0, a0, a1
>>>        sfence.vma
>>> @@ -145,7 +159,9 @@ secondary_start_sbi:
>>>        slli a3, a0, LGREG
>>>        la a4, __cpu_up_stack_pointer
>>> +    XIP_FIXUP_OFFSET a4
>>>        la a5, __cpu_up_task_pointer
>>> +    XIP_FIXUP_OFFSET a5
>>>        add a4, a3, a4
>>>        add a5, a3, a5
>>>        REG_L sp, (a4)
>>> @@ -157,6 +173,7 @@ secondary_start_common:
>>>    #ifdef CONFIG_MMU
>>>        /* Enable virtual memory and relocate to virtual address */
>>>        la a0, swapper_pg_dir
>>> +    XIP_FIXUP_OFFSET a0
>>>        call relocate
>>>    #endif
>>>        call setup_trap_vector
>>> @@ -237,12 +254,33 @@ pmp_done:
>>>    .Lgood_cores:
>>>    #endif
>>> +#ifndef CONFIG_XIP_KERNEL
>>>        /* Pick one hart to run the main boot sequence */
>>>        la a3, hart_lottery
>>>        li a2, 1
>>>        amoadd.w a3, a2, (a3)
>>>        bnez a3, .Lsecondary_start
>>> +#else
>>> +    /* hart_lottery in flash contains a magic number */
>>> +    la a3, hart_lottery
>>> +    mv a2, a3
>>> +    XIP_FIXUP_OFFSET a2
>>> +    lw t1, (a3)
>>> +    amoswap.w t0, t1, (a2)
>>> +    /* first time here if hart_lottery in RAM is not set */
>>> +    beq t0, t1, .Lsecondary_start
>>> +
>>> +    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
>>> @@ -252,15 +290,18 @@ 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
>>> +    XIP_FIXUP_OFFSET a2
>>>        REG_S a0, (a2)
>>>        /* Initialize page tables and relocate to virtual addresses */
>>>        la sp, init_thread_union + THREAD_SIZE
>>> +    XIP_FIXUP_OFFSET sp
>>>    #ifdef CONFIG_BUILTIN_DTB
>>>        la a0, __dtb_start
>>>    #else
>>> @@ -269,6 +310,7 @@ clear_bss_done:
>>>        call setup_vm
>>>    #ifdef CONFIG_MMU
>>>        la a0, early_pg_dir
>>> +    XIP_FIXUP_OFFSET a0
>>>        call relocate
>>>    #endif /* CONFIG_MMU */
>>> @@ -293,7 +335,9 @@ clear_bss_done:
>>>        slli a3, a0, LGREG
>>>        la a1, __cpu_up_stack_pointer
>>> +    XIP_FIXUP_OFFSET a1
>>>        la a2, __cpu_up_task_pointer
>>> +    XIP_FIXUP_OFFSET a2
>>>        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 30e4af0fd50c..2ddf654c72bb 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(0xC001BEEF)
>>> +#endif
>>> +;
>>>    unsigned long boot_cpu_hartid;
>>>    static DEFINE_PER_CPU(struct cpu, cpu_devices);
>>> @@ -254,7 +258,7 @@ 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(__va(XIP_FIXUP(dtb_early_pa))))
>>>            unflatten_device_tree();
>>>        else
>>>            pr_err("No DTB found in kernel mappings\n");
>>> @@ -266,7 +270,7 @@ void __init setup_arch(char **cmdline_p)
>>>        if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
>>>            protect_kernel_text_data();
>>> -#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)
>>> +#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) && 
>>> !defined(CONFIG_XIP_KERNEL)
>>>        protect_kernel_linear_mapping_text_rodata();
>>>    #endif
>>> diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S 
>>> b/arch/riscv/kernel/vmlinux-xip.lds.S
>>> new file mode 100644
>>> index 000000000000..4b29b9917f99
>>> --- /dev/null
>>> +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
>>> @@ -0,0 +1,133 @@
>>> +/* 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
>>> + */
>>> +
>>> +#include <asm/pgtable.h>
>>> +#define LOAD_OFFSET KERNEL_LINK_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 */
>>> +    . = LOAD_OFFSET;
>>> +    _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 */
>>> +    . = LOAD_OFFSET + XIP_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 0726c05e0336..0a59b65cf789 100644
>>> --- a/arch/riscv/kernel/vmlinux.lds.S
>>> +++ b/arch/riscv/kernel/vmlinux.lds.S
>>> @@ -4,8 +4,13 @@
>>>     * Copyright (C) 2017 SiFive
>>>     */
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#include "vmlinux-xip.lds.S"
>>> +#else
>>> +
>>>    #include <asm/pgtable.h>
>>>    #define LOAD_OFFSET KERNEL_LINK_ADDR
>>> +
>>>    #include <asm/vmlinux.lds.h>
>>>    #include <asm/page.h>
>>>    #include <asm/cache.h>
>>> @@ -133,3 +138,4 @@ SECTIONS
>>>        DISCARDS
>>>    }
>>> +#endif /* CONFIG_XIP_KERNEL */
>>> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
>>> index 093f3a96ecfc..9961573f9a55 100644
>>> --- a/arch/riscv/mm/init.c
>>> +++ b/arch/riscv/mm/init.c
>>> @@ -27,6 +27,9 @@
>>>    unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
>>>    EXPORT_SYMBOL(kernel_virt_addr);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define kernel_virt_addr       (*((unsigned long 
>>> *)XIP_FIXUP(&kernel_virt_addr)))
>>> +#endif
>>>    unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
>>>                                __page_aligned_bss;
>>> @@ -34,8 +37,8 @@ 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);
>>> @@ -118,6 +121,10 @@ void __init setup_bootmem(void)
>>>        phys_addr_t dram_end = memblock_end_of_DRAM();
>>>        phys_addr_t max_mapped_addr = __pa(~(ulong)0);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +    vmlinux_start = __pa_symbol(&_sdata);
>>> +#endif
>>> +
>>>        /* The maximal physical memory size is -PAGE_OFFSET. */
>>>        memblock_enforce_memory_limit(-PAGE_OFFSET);
>>> @@ -159,17 +166,44 @@ void __init setup_bootmem(void)
>>>        memblock_allow_resize();
>>>    }
>>> +#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
>>>    /* Offset between linear mapping virtual address and kernel load 
>>> address */
>>>    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
>>>    /* Offset between kernel mapping virtual address and kernel load 
>>> address */
>>>    unsigned long va_kernel_pa_offset;
>>>    EXPORT_SYMBOL(va_kernel_pa_offset);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define va_kernel_pa_offset    (*((unsigned long 
>>> *)XIP_FIXUP(&va_kernel_pa_offset)))
>>> +#endif
>>> +unsigned long va_kernel_xip_pa_offset;
>>> +EXPORT_SYMBOL(va_kernel_xip_pa_offset);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define va_kernel_xip_pa_offset        (*((unsigned long 
>>> *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
>>> +#endif
>>>    unsigned long pfn_base;
>>>    EXPORT_SYMBOL(pfn_base);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define pfn_base       (*((unsigned long *)XIP_FIXUP(&pfn_base)))
>>> +#endif
>>>    pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>>>    pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>>> @@ -177,6 +211,12 @@ pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
>>>    pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#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))
>>> +#endif /* CONFIG_XIP_KERNEL */
>>> +
>>>    void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, 
>>> pgprot_t prot)
>>>    {
>>>        unsigned long addr = __fix_to_virt(idx);
>>> @@ -252,6 +292,12 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
>>>    pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>>    pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
>>> +#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_pmd))
>>> +#define early_pmd      ((pmd_t *)XIP_FIXUP(early_pmd))
>>> +#endif /* CONFIG_XIP_KERNEL */
>>> +
>>>    static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
>>>    {
>>>        /* Before MMU is enabled */
>>> @@ -368,6 +414,19 @@ 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_PHYS_RAM_BASE;
>>> +    size_t sz = (size_t)(end - from + 1);
>>> +
>>> +    memcpy(to, from, sz);
>>> +}
>>> +#endif
>>> +
>>>    /*
>>>     * setup_vm() is called from head.S with MMU-off.
>>>     *
>>> @@ -387,7 +446,35 @@ static uintptr_t __init 
>>> best_map_size(phys_addr_t base, phys_addr_t size)
>>>    #endif
>>>    uintptr_t load_pa, load_sz;
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +#define load_pa        (*((uintptr_t *)XIP_FIXUP(&load_pa)))
>>> +#define load_sz        (*((uintptr_t *)XIP_FIXUP(&load_sz)))
>>> +#endif
>>> +
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +uintptr_t xiprom, xiprom_sz;
>>> +#define xiprom_sz      (*((uintptr_t *)XIP_FIXUP(&xiprom_sz)))
>>> +#define xiprom         (*((uintptr_t *)XIP_FIXUP(&xiprom)))
>>> +static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t 
>>> map_size)
>>> +{
>>> +    uintptr_t va, end_va;
>>> +
>>> +    /* Map the flash resident part */
>>> +    end_va = kernel_virt_addr + xiprom_sz;
>>> +    for (va = kernel_virt_addr; va < end_va; va += map_size)
>>> +        create_pgd_mapping(pgdir, va,
>>> +                   xiprom + (va - kernel_virt_addr),
>>> +                   map_size, PAGE_KERNEL_EXEC);
>>> +
>>> +    /* Map the data in RAM */
>>> +    end_va = kernel_virt_addr + XIP_OFFSET + load_sz;
>>> +    for (va = kernel_virt_addr + XIP_OFFSET; va < end_va; va += 
>>> map_size)
>>> +        create_pgd_mapping(pgdir, va,
>>> +                   load_pa + (va - (kernel_virt_addr + XIP_OFFSET)),
>>> +                   map_size, PAGE_KERNEL);
>>> +}
>>> +#else
>>>    static void __init create_kernel_page_table(pgd_t *pgdir, 
>>> uintptr_t map_size)
>>>    {
>>>        uintptr_t va, end_va;
>>> @@ -398,16 +485,28 @@ static void __init 
>>> create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
>>>                       load_pa + (va - kernel_virt_addr),
>>>                       map_size, PAGE_KERNEL_EXEC);
>>>    }
>>> +#endif
>>>    asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>    {
>>> -    uintptr_t pa;
>>> +    uintptr_t __maybe_unused pa;
>>>        uintptr_t map_size;
>>>    #ifndef __PAGETABLE_PMD_FOLDED
>>>        pmd_t fix_bmap_spmd, fix_bmap_epmd;
>>>    #endif
>>> +
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +    xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
>>> +    xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
>>> +
>>> +    load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
>>> +    load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
>>> +
>>> +    va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
>>> +#else
>>>        load_pa = (uintptr_t)(&_start);
>>>        load_sz = (uintptr_t)(&_end) - load_pa;
>>> +#endif
>>>        va_pa_offset = PAGE_OFFSET - load_pa;
>>>        va_kernel_pa_offset = kernel_virt_addr - load_pa;
>>> @@ -441,8 +540,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>        /* Setup trampoline PGD and PMD */
>>>        create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>>                   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
>>> +#ifdef CONFIG_XIP_KERNEL
>>> +    create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>>> +               xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
>>> +#else
>>>        create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
>>>                   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
>>> +#endif
>>>    #else
>>>        /* Setup trampoline PGD */
>>>        create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
>>> @@ -474,7 +578,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>         * whereas dtb_early_va will be used before setup_vm_final 
>>> installs
>>>         * the linear mapping.
>>>         */
>>> -    dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
>>> +    dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>>>    #endif /* CONFIG_BUILTIN_DTB */
>>>    #else
>>>    #ifndef CONFIG_BUILTIN_DTB
>>> @@ -486,7 +590,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>                   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
>>>        dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & 
>>> (PGDIR_SIZE - 1));
>>>    #else /* CONFIG_BUILTIN_DTB */
>>> -    dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
>>> +    dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
>>>    #endif /* CONFIG_BUILTIN_DTB */
>>>    #endif
>>>        dtb_early_pa = dtb_pa;
>>> @@ -522,7 +626,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
>>>    #endif
>>>    }
>>> -#ifdef CONFIG_64BIT
>>> +#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
>>>    void protect_kernel_linear_mapping_text_rodata(void)
>>>    {
>>>        unsigned long text_start = (unsigned long)lm_alias(_start);
>>>
>>
> 
>
David Hildenbrand April 9, 2021, 12:07 p.m. UTC | #4
On 09.04.21 13:39, Alex Ghiti wrote:
> Hi David,
> 
> Le 4/9/21 à 4:23 AM, David Hildenbrand a écrit :
>> On 09.04.21 09:14, Alex Ghiti wrote:
>>> Le 4/9/21 à 2:51 AM, Alexandre Ghiti a écrit :
>>>> From: Vitaly Wool <vitaly.wool@konsulko.com>
>>>>
>>>> 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. 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 for the time being only work on MMU-enabled
>>>> kernels.
>>>>
>>> I added linux-mm and linux-arch to get feedbacks because I noticed that
>>> DEBUG_VM_PGTABLE fails for SPARSEMEM (it works for FLATMEM but I think
>>> it does not do what is expected): the fact that we don't have any struct
>>> page to back the text and rodata in flash is the problem but to which
>>> extent ?
>>
>> Just wondering, why can't we create a memmap for that memory -- or is it
>> even desireable to not do that explicity? There might be some nasty side
>> effects when not having a memmap for text and rodata.
> 
> 
> Do you have examples of such effects ? Any feature that will not work
> without that ?
> 

At least if it's not part of /proc/iomem in any way (maybe "System RAM" 
is not what we want without a memmap, TBD), kexec-tools won't be able to 
handle it properly e.g., for kdump. But not sure if that is really 
relevant in your setup.

Regarding other features, anything that does a pfn_valid(), 
pfn_to_page() or pfn_to_online_page() would behave differently now -- 
assuming the kernel doesn't fall into a section with other System RAM 
(whereby we would still allocate the memmap for the whole section).

I guess you might stumble over some surprises in some code paths, but 
nothing really comes to mind. Not sure if your zeropage is part of the 
kernel image on RISC-V (I remember that we sometimes need a memmap 
there, but I might be wrong)?

I assume you still somehow create the direct mapping for the kernel, 
right? So it's really some memory region with a direct mapping but 
without a memmap (and right now, without a resource), correct?

[...]

>>
>> Also, will that memory properly be exposed in the resource tree as
>> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
>> won't work as expected - the kernel won't be included in a dump.
> 
> 
> I have just checked and it does not appear in /proc/iomem.
> 
> Ok your conclusion would be to have struct page, I'm going to implement
> this version then using memblock as you described.

Let's first evaluate what the harm could be. You could (and should?) 
create the kernel resource manually - IIRC, that's independent of the 
memmap/memblock thing.

@Mike, what's your take on not having a memmap for kernel text and ro data?
Mike Rapoport April 9, 2021, 12:12 p.m. UTC | #5
On Fri, Apr 09, 2021 at 07:39:59AM -0400, Alex Ghiti wrote:
> Hi David,
> 
> Le 4/9/21 à 4:23 AM, David Hildenbrand a écrit :
> > On 09.04.21 09:14, Alex Ghiti wrote:
> > > Le 4/9/21 à 2:51 AM, Alexandre Ghiti a écrit :
> > > > From: Vitaly Wool <vitaly.wool@konsulko.com>
> > > > 
> > > > 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. 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 for the time being only work on MMU-enabled
> > > > kernels.
> > > > 
> > > I added linux-mm and linux-arch to get feedbacks because I noticed that
> > > DEBUG_VM_PGTABLE fails for SPARSEMEM (it works for FLATMEM but I think
> > > it does not do what is expected): the fact that we don't have any struct
> > > page to back the text and rodata in flash is the problem but to which
> > > extent ?
> > 
> > Just wondering, why can't we create a memmap for that memory -- or is it
> > even desireable to not do that explicity? There might be some nasty side
> > effects when not having a memmap for text and rodata.
> 
> 
> Do you have examples of such effects ? Any feature that will not work
> without that ?
> 
> 
> > 
> > I would assume stimply exposing the physical memory range to memblock as
> > RAM and marking it reserved would create a memmap that's fully
> > initialized like any bootmem (PG_reserved).
> > 
> > Or is there a reason why we cannot do that?
> 
> 
> I did not want to do that if it was not needed as the overall goal of XIP
> kernel is to save RAM (I may be cheap but 16MB backed by struct page
> represents ~220KB).
> 
> 
> 
> > 
> > Also, will that memory properly be exposed in the resource tree as
> > System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
> > won't work as expected - the kernel won't be included in a dump.
 
Do we really need a XIP kernel to included in kdump? 
And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)

> I have just checked and it does not appear in /proc/iomem.
> 
> Ok your conclusion would be to have struct page, I'm going to implement this
> version then using memblock as you described.

I'm not sure this is required. With XIP kernel text never gets into RAM, so
it does not seem to require struct page.

XIP by definition has some limitations relatively to "normal" operation,
so lack of kdump could be one of them. 

I might be wrong, but IMHO, artificially creating a memory map for part of
flash would cause more problems in the long run.

BTW, how does XIP account the kernel text on other architectures that
implement it?
 
> Thanks David,
> 
> Alex
> 
> > 
> > 
> > > 
> > > Thanks,
> > > 
> > > Alex
> > > 
> > > > Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> [ Rebase on top of "Move
> > > > kernel mapping outside the linear mapping ]
> > > > Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
> > > > ---
> > > > 
> > > > Changes 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.
> > > > Changes in v3:
> > > > - rebased against latest for-next
> > > > - XIP address fixup macro now takes an argument
> > > > - SMP related fixes
> > > > Changes in v4:
> > > > - rebased against the current for-next
> > > > - less #ifdef's in C/ASM code
> > > > - dedicated XIP_FIXUP_OFFSET assembler macro in head.S
> > > > - C-specific definitions moved into #ifndef __ASSEMBLY__
> > > > - Fixed multi-core boot
> > > > Changes in v5:
> > > > - fixed build error for non-XIP kernels
> > > > Changes in v6:
> > > > - XIP_PHYS_RAM_BASE config option renamed to PHYS_RAM_BASE
> > > > - added PHYS_RAM_BASE_FIXED config flag to allow usage of
> > > >     PHYS_RAM_BASE in non-XIP configurations if needed
> > > > - XIP_FIXUP macro rewritten with a tempoarary variable to avoid side
> > > >     effects
> > > > - fixed crash for non-XIP kernels that don't use built-in DTB
> > > > Changes in v7:
> > > > - Fix pfn_base that required FIXUP
> > > > - Fix copy_data which lacked + 1 in size to copy
> > > > - Fix pfn_valid for FLATMEM
> > > > - Rebased on top of "Move kernel mapping outside the linear mapping":
> > > >     this is the biggest change and affected mm/init.c,
> > > >     kernel/vmlinux-xip.lds.S and include/asm/pgtable.h: XIP
> > > > kernel is now
> > > >     mapped like 'normal' kernel at the end of the address space.
> > > > 
> > > >    arch/riscv/Kconfig                  |  51 ++++++++++-
> > > >    arch/riscv/Makefile                 |   8 +-
> > > >    arch/riscv/boot/Makefile            |  13 +++
> > > >    arch/riscv/include/asm/page.h       |  28 ++++++
> > > >    arch/riscv/include/asm/pgtable.h    |  25 +++++-
> > > >    arch/riscv/kernel/head.S            |  46 +++++++++-
> > > >    arch/riscv/kernel/head.h            |   3 +
> > > >    arch/riscv/kernel/setup.c           |  10 ++-
> > > >    arch/riscv/kernel/vmlinux-xip.lds.S | 133
> > > > ++++++++++++++++++++++++++++
> > > >    arch/riscv/kernel/vmlinux.lds.S     |   6 ++
> > > >    arch/riscv/mm/init.c                | 118 ++++++++++++++++++++++--
> > > >    11 files changed, 424 insertions(+), 17 deletions(-)
> > > >    create mode 100644 arch/riscv/kernel/vmlinux-xip.lds.S
> > > > 
> > > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > > > index 8ea60a0a19ae..4d0153805927 100644
> > > > --- a/arch/riscv/Kconfig
> > > > +++ b/arch/riscv/Kconfig
> > > > @@ -28,7 +28,7 @@ config RISCV
> > > >        select ARCH_HAS_PTE_SPECIAL
> > > >        select ARCH_HAS_SET_DIRECT_MAP
> > > >        select ARCH_HAS_SET_MEMORY
> > > > -    select ARCH_HAS_STRICT_KERNEL_RWX if MMU
> > > > +    select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
> > > >        select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> > > >        select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
> > > >        select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
> > > > @@ -441,7 +441,7 @@ 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
> > > > @@ -465,11 +465,56 @@ config STACKPROTECTOR_PER_TASK
> > > >        def_bool y
> > > >        depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
> > > > +config PHYS_RAM_BASE_FIXED
> > > > +    bool "Explicitly specified physical RAM address"
> > > > +    default n
> > > > +
> > > > +config PHYS_RAM_BASE
> > > > +    hex "Platform Physical RAM address"
> > > > +    depends on PHYS_RAM_BASE_FIXED
> > > > +    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.
> > > > +
> > > > +config XIP_KERNEL
> > > > +    bool "Kernel Execute-In-Place from ROM"
> > > > +    depends on MMU
> > > > +    select PHYS_RAM_BASE_FIXED
> > > > +    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.
> > > > +
> > > >    endmenu
> > > >    config BUILTIN_DTB
> > > > -    def_bool n
> > > > +    bool
> > > >        depends on OF
> > > > +    default y if XIP_KERNEL
> > > >    menu "Power management options"
> > > > diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> > > > index 1368d943f1f3..8fcbec03974d 100644
> > > > --- a/arch/riscv/Makefile
> > > > +++ b/arch/riscv/Makefile
> > > > @@ -82,7 +82,11 @@ 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
> > > > @@ -95,12 +99,14 @@ PHONY += vdso_install
> > > >    vdso_install:
> > > >        $(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
> > > > +ifneq ($(CONFIG_XIP_KERNEL),y)
> > > >    ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),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/page.h
> > > > b/arch/riscv/include/asm/page.h
> > > > index 22cfb2be60dc..6fe0ff8c8fa9 100644
> > > > --- a/arch/riscv/include/asm/page.h
> > > > +++ b/arch/riscv/include/asm/page.h
> > > > @@ -91,6 +91,9 @@ typedef struct page *pgtable_t;
> > > >    #ifdef CONFIG_MMU
> > > >    extern unsigned long va_pa_offset;
> > > >    extern unsigned long va_kernel_pa_offset;
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +extern unsigned long va_kernel_xip_pa_offset;
> > > > +#endif
> > > >    extern unsigned long pfn_base;
> > > >    #define ARCH_PFN_OFFSET        (pfn_base)
> > > >    #else
> > > > @@ -102,11 +105,29 @@ extern unsigned long pfn_base;
> > > >    extern unsigned long kernel_virt_addr;
> > > >    #define linear_mapping_pa_to_va(x)    ((void *)((unsigned
> > > > long)(x) + va_pa_offset))
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define kernel_mapping_pa_to_va(y)    ({                        \
> > > > +    unsigned long _y = y;                                \
> > > > +    (_y >= CONFIG_PHYS_RAM_BASE) ?                            \
> > > > +        (void *)((unsigned long)(_y) + va_kernel_pa_offset +
> > > > XIP_OFFSET) :    \
> > > > +        (void *)((unsigned long)(_y) +
> > > > va_kernel_xip_pa_offset);        \
> > > > +    })
> > > > +#else
> > > >    #define kernel_mapping_pa_to_va(x)    ((void *)((unsigned
> > > > long)(x) + va_kernel_pa_offset))
> > > > +#endif
> > > >    #define __pa_to_va_nodebug(x)        linear_mapping_pa_to_va(x)
> > > >    #define linear_mapping_va_to_pa(x)    ((unsigned long)(x) -
> > > > va_pa_offset)
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define kernel_mapping_va_to_pa(y) ({                        \
> > > > +    unsigned long _y = y;                            \
> > > > +    (_y < kernel_virt_addr + XIP_OFFSET) ?                    \
> > > > +        ((unsigned long)(_y) - va_kernel_xip_pa_offset) :        \
> > > > +        ((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET);    \
> > > > +    })
> > > > +#else
> > > >    #define kernel_mapping_va_to_pa(x)    ((unsigned long)(x) -
> > > > va_kernel_pa_offset)
> > > > +#endif
> > > >    #define __va_to_pa_nodebug(x)    ({                        \
> > > >        unsigned long _x = x;                            \
> > > >        (_x < kernel_virt_addr) ?                        \
> > > > @@ -139,9 +160,16 @@ extern phys_addr_t
> > > > __phys_addr_symbol(unsigned long x);
> > > >    #define phys_to_page(paddr)    (pfn_to_page(phys_to_pfn(paddr)))
> > > >    #ifdef CONFIG_FLATMEM
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define pfn_valid(pfn) \
> > > > +    ((((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET)
> > > > < max_mapnr)) ||    \
> > > > +        ((pfn) >= PFN_DOWN(CONFIG_XIP_PHYS_ADDR) &&                \
> > > > +        (((pfn) - PFN_DOWN(CONFIG_XIP_PHYS_ADDR)) < XIP_OFFSET)))
> > > > +#else
> > > >    #define pfn_valid(pfn) \
> > > >        (((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET)
> > > > < max_mapnr))
> > > >    #endif
> > > > +#endif
> > > >    #endif /* __ASSEMBLY__ */
> > > > diff --git a/arch/riscv/include/asm/pgtable.h
> > > > b/arch/riscv/include/asm/pgtable.h
> > > > index 80e63a93e903..c2dc4f83eed8 100644
> > > > --- a/arch/riscv/include/asm/pgtable.h
> > > > +++ b/arch/riscv/include/asm/pgtable.h
> > > > @@ -64,6 +64,19 @@
> > > >    #define FIXADDR_SIZE     PGDIR_SIZE
> > > >    #endif
> > > >    #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
> > > > +
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define XIP_OFFSET        SZ_8M
> > > > +#define XIP_FIXUP(addr) ({                            \
> > > > +    uintptr_t __a = (uintptr_t)(addr);                    \
> > > > +    (__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR
> > > > + SZ_16M) ?    \
> > > > +        __a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE -
> > > > XIP_OFFSET :\
> > > > +        __a;                                \
> > > > +    })
> > > > +#else
> > > > +#define XIP_FIXUP(addr)        (addr)
> > > > +#endif /* CONFIG_XIP_KERNEL */
> > > > +
> > > >    #endif
> > > >    #ifndef __ASSEMBLY__
> > > > @@ -499,8 +512,16 @@ static inline int
> > > > ptep_clear_flush_young(struct vm_area_struct *vma,
> > > >    #define kern_addr_valid(addr)   (1) /* FIXME */
> > > >    extern char _start[];
> > > > -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);
> > > >    void misc_mem_init(void);
> > > > diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> > > > index 6cb05f22e52a..89cc58ab52b4 100644
> > > > --- a/arch/riscv/kernel/head.S
> > > > +++ b/arch/riscv/kernel/head.S
> > > > @@ -9,11 +9,23 @@
> > > >    #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
> > > > +    REG_L t0, _xip_fixup
> > > > +    add \reg, \reg, t0
> > > > +.endm
> > > > +_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR
> > > > - XIP_OFFSET
> > > > +#else
> > > > +.macro XIP_FIXUP_OFFSET reg
> > > > +.endm
> > > > +#endif /* CONFIG_XIP_KERNEL */
> > > > +
> > > >    __HEAD
> > > >    ENTRY(_start)
> > > >        /*
> > > > @@ -70,6 +82,7 @@ pe_head_start:
> > > >    relocate:
> > > >        /* Relocate return address */
> > > >        la a1, kernel_virt_addr
> > > > +    XIP_FIXUP_OFFSET a1
> > > >        REG_L a1, 0(a1)
> > > >        la a2, _start
> > > >        sub a1, a1, a2
> > > > @@ -92,6 +105,7 @@ relocate:
> > > >         * to ensure the new translations are in use.
> > > >         */
> > > >        la a0, trampoline_pg_dir
> > > > +    XIP_FIXUP_OFFSET a0
> > > >        srl a0, a0, PAGE_SHIFT
> > > >        or a0, a0, a1
> > > >        sfence.vma
> > > > @@ -145,7 +159,9 @@ secondary_start_sbi:
> > > >        slli a3, a0, LGREG
> > > >        la a4, __cpu_up_stack_pointer
> > > > +    XIP_FIXUP_OFFSET a4
> > > >        la a5, __cpu_up_task_pointer
> > > > +    XIP_FIXUP_OFFSET a5
> > > >        add a4, a3, a4
> > > >        add a5, a3, a5
> > > >        REG_L sp, (a4)
> > > > @@ -157,6 +173,7 @@ secondary_start_common:
> > > >    #ifdef CONFIG_MMU
> > > >        /* Enable virtual memory and relocate to virtual address */
> > > >        la a0, swapper_pg_dir
> > > > +    XIP_FIXUP_OFFSET a0
> > > >        call relocate
> > > >    #endif
> > > >        call setup_trap_vector
> > > > @@ -237,12 +254,33 @@ pmp_done:
> > > >    .Lgood_cores:
> > > >    #endif
> > > > +#ifndef CONFIG_XIP_KERNEL
> > > >        /* Pick one hart to run the main boot sequence */
> > > >        la a3, hart_lottery
> > > >        li a2, 1
> > > >        amoadd.w a3, a2, (a3)
> > > >        bnez a3, .Lsecondary_start
> > > > +#else
> > > > +    /* hart_lottery in flash contains a magic number */
> > > > +    la a3, hart_lottery
> > > > +    mv a2, a3
> > > > +    XIP_FIXUP_OFFSET a2
> > > > +    lw t1, (a3)
> > > > +    amoswap.w t0, t1, (a2)
> > > > +    /* first time here if hart_lottery in RAM is not set */
> > > > +    beq t0, t1, .Lsecondary_start
> > > > +
> > > > +    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
> > > > @@ -252,15 +290,18 @@ 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
> > > > +    XIP_FIXUP_OFFSET a2
> > > >        REG_S a0, (a2)
> > > >        /* Initialize page tables and relocate to virtual addresses */
> > > >        la sp, init_thread_union + THREAD_SIZE
> > > > +    XIP_FIXUP_OFFSET sp
> > > >    #ifdef CONFIG_BUILTIN_DTB
> > > >        la a0, __dtb_start
> > > >    #else
> > > > @@ -269,6 +310,7 @@ clear_bss_done:
> > > >        call setup_vm
> > > >    #ifdef CONFIG_MMU
> > > >        la a0, early_pg_dir
> > > > +    XIP_FIXUP_OFFSET a0
> > > >        call relocate
> > > >    #endif /* CONFIG_MMU */
> > > > @@ -293,7 +335,9 @@ clear_bss_done:
> > > >        slli a3, a0, LGREG
> > > >        la a1, __cpu_up_stack_pointer
> > > > +    XIP_FIXUP_OFFSET a1
> > > >        la a2, __cpu_up_task_pointer
> > > > +    XIP_FIXUP_OFFSET a2
> > > >        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 30e4af0fd50c..2ddf654c72bb 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(0xC001BEEF)
> > > > +#endif
> > > > +;
> > > >    unsigned long boot_cpu_hartid;
> > > >    static DEFINE_PER_CPU(struct cpu, cpu_devices);
> > > > @@ -254,7 +258,7 @@ 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(__va(XIP_FIXUP(dtb_early_pa))))
> > > >            unflatten_device_tree();
> > > >        else
> > > >            pr_err("No DTB found in kernel mappings\n");
> > > > @@ -266,7 +270,7 @@ void __init setup_arch(char **cmdline_p)
> > > >        if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
> > > >            protect_kernel_text_data();
> > > > -#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)
> > > > +#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) &&
> > > > !defined(CONFIG_XIP_KERNEL)
> > > >        protect_kernel_linear_mapping_text_rodata();
> > > >    #endif
> > > > diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S
> > > > b/arch/riscv/kernel/vmlinux-xip.lds.S
> > > > new file mode 100644
> > > > index 000000000000..4b29b9917f99
> > > > --- /dev/null
> > > > +++ b/arch/riscv/kernel/vmlinux-xip.lds.S
> > > > @@ -0,0 +1,133 @@
> > > > +/* 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
> > > > + */
> > > > +
> > > > +#include <asm/pgtable.h>
> > > > +#define LOAD_OFFSET KERNEL_LINK_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 */
> > > > +    . = LOAD_OFFSET;
> > > > +    _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 */
> > > > +    . = LOAD_OFFSET + XIP_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 0726c05e0336..0a59b65cf789 100644
> > > > --- a/arch/riscv/kernel/vmlinux.lds.S
> > > > +++ b/arch/riscv/kernel/vmlinux.lds.S
> > > > @@ -4,8 +4,13 @@
> > > >     * Copyright (C) 2017 SiFive
> > > >     */
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#include "vmlinux-xip.lds.S"
> > > > +#else
> > > > +
> > > >    #include <asm/pgtable.h>
> > > >    #define LOAD_OFFSET KERNEL_LINK_ADDR
> > > > +
> > > >    #include <asm/vmlinux.lds.h>
> > > >    #include <asm/page.h>
> > > >    #include <asm/cache.h>
> > > > @@ -133,3 +138,4 @@ SECTIONS
> > > >        DISCARDS
> > > >    }
> > > > +#endif /* CONFIG_XIP_KERNEL */
> > > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > > > index 093f3a96ecfc..9961573f9a55 100644
> > > > --- a/arch/riscv/mm/init.c
> > > > +++ b/arch/riscv/mm/init.c
> > > > @@ -27,6 +27,9 @@
> > > >    unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
> > > >    EXPORT_SYMBOL(kernel_virt_addr);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define kernel_virt_addr       (*((unsigned long
> > > > *)XIP_FIXUP(&kernel_virt_addr)))
> > > > +#endif
> > > >    unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
> > > >                                __page_aligned_bss;
> > > > @@ -34,8 +37,8 @@ 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);
> > > > @@ -118,6 +121,10 @@ void __init setup_bootmem(void)
> > > >        phys_addr_t dram_end = memblock_end_of_DRAM();
> > > >        phys_addr_t max_mapped_addr = __pa(~(ulong)0);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +    vmlinux_start = __pa_symbol(&_sdata);
> > > > +#endif
> > > > +
> > > >        /* The maximal physical memory size is -PAGE_OFFSET. */
> > > >        memblock_enforce_memory_limit(-PAGE_OFFSET);
> > > > @@ -159,17 +166,44 @@ void __init setup_bootmem(void)
> > > >        memblock_allow_resize();
> > > >    }
> > > > +#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
> > > >    /* Offset between linear mapping virtual address and kernel
> > > > load address */
> > > >    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
> > > >    /* Offset between kernel mapping virtual address and kernel
> > > > load address */
> > > >    unsigned long va_kernel_pa_offset;
> > > >    EXPORT_SYMBOL(va_kernel_pa_offset);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define va_kernel_pa_offset    (*((unsigned long
> > > > *)XIP_FIXUP(&va_kernel_pa_offset)))
> > > > +#endif
> > > > +unsigned long va_kernel_xip_pa_offset;
> > > > +EXPORT_SYMBOL(va_kernel_xip_pa_offset);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define va_kernel_xip_pa_offset        (*((unsigned long
> > > > *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
> > > > +#endif
> > > >    unsigned long pfn_base;
> > > >    EXPORT_SYMBOL(pfn_base);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define pfn_base       (*((unsigned long *)XIP_FIXUP(&pfn_base)))
> > > > +#endif
> > > >    pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
> > > >    pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
> > > > @@ -177,6 +211,12 @@ pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
> > > >    pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#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))
> > > > +#endif /* CONFIG_XIP_KERNEL */
> > > > +
> > > >    void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys,
> > > > pgprot_t prot)
> > > >    {
> > > >        unsigned long addr = __fix_to_virt(idx);
> > > > @@ -252,6 +292,12 @@ pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
> > > >    pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
> > > >    pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
> > > > +#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_pmd))
> > > > +#define early_pmd      ((pmd_t *)XIP_FIXUP(early_pmd))
> > > > +#endif /* CONFIG_XIP_KERNEL */
> > > > +
> > > >    static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
> > > >    {
> > > >        /* Before MMU is enabled */
> > > > @@ -368,6 +414,19 @@ 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_PHYS_RAM_BASE;
> > > > +    size_t sz = (size_t)(end - from + 1);
> > > > +
> > > > +    memcpy(to, from, sz);
> > > > +}
> > > > +#endif
> > > > +
> > > >    /*
> > > >     * setup_vm() is called from head.S with MMU-off.
> > > >     *
> > > > @@ -387,7 +446,35 @@ static uintptr_t __init
> > > > best_map_size(phys_addr_t base, phys_addr_t size)
> > > >    #endif
> > > >    uintptr_t load_pa, load_sz;
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +#define load_pa        (*((uintptr_t *)XIP_FIXUP(&load_pa)))
> > > > +#define load_sz        (*((uintptr_t *)XIP_FIXUP(&load_sz)))
> > > > +#endif
> > > > +
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +uintptr_t xiprom, xiprom_sz;
> > > > +#define xiprom_sz      (*((uintptr_t *)XIP_FIXUP(&xiprom_sz)))
> > > > +#define xiprom         (*((uintptr_t *)XIP_FIXUP(&xiprom)))
> > > > +static void __init create_kernel_page_table(pgd_t *pgdir,
> > > > uintptr_t map_size)
> > > > +{
> > > > +    uintptr_t va, end_va;
> > > > +
> > > > +    /* Map the flash resident part */
> > > > +    end_va = kernel_virt_addr + xiprom_sz;
> > > > +    for (va = kernel_virt_addr; va < end_va; va += map_size)
> > > > +        create_pgd_mapping(pgdir, va,
> > > > +                   xiprom + (va - kernel_virt_addr),
> > > > +                   map_size, PAGE_KERNEL_EXEC);
> > > > +
> > > > +    /* Map the data in RAM */
> > > > +    end_va = kernel_virt_addr + XIP_OFFSET + load_sz;
> > > > +    for (va = kernel_virt_addr + XIP_OFFSET; va < end_va; va +=
> > > > map_size)
> > > > +        create_pgd_mapping(pgdir, va,
> > > > +                   load_pa + (va - (kernel_virt_addr + XIP_OFFSET)),
> > > > +                   map_size, PAGE_KERNEL);
> > > > +}
> > > > +#else
> > > >    static void __init create_kernel_page_table(pgd_t *pgdir,
> > > > uintptr_t map_size)
> > > >    {
> > > >        uintptr_t va, end_va;
> > > > @@ -398,16 +485,28 @@ static void __init
> > > > create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
> > > >                       load_pa + (va - kernel_virt_addr),
> > > >                       map_size, PAGE_KERNEL_EXEC);
> > > >    }
> > > > +#endif
> > > >    asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> > > >    {
> > > > -    uintptr_t pa;
> > > > +    uintptr_t __maybe_unused pa;
> > > >        uintptr_t map_size;
> > > >    #ifndef __PAGETABLE_PMD_FOLDED
> > > >        pmd_t fix_bmap_spmd, fix_bmap_epmd;
> > > >    #endif
> > > > +
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +    xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
> > > > +    xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
> > > > +
> > > > +    load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
> > > > +    load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
> > > > +
> > > > +    va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
> > > > +#else
> > > >        load_pa = (uintptr_t)(&_start);
> > > >        load_sz = (uintptr_t)(&_end) - load_pa;
> > > > +#endif
> > > >        va_pa_offset = PAGE_OFFSET - load_pa;
> > > >        va_kernel_pa_offset = kernel_virt_addr - load_pa;
> > > > @@ -441,8 +540,13 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> > > >        /* Setup trampoline PGD and PMD */
> > > >        create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
> > > >                   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
> > > > +#ifdef CONFIG_XIP_KERNEL
> > > > +    create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
> > > > +               xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
> > > > +#else
> > > >        create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
> > > >                   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
> > > > +#endif
> > > >    #else
> > > >        /* Setup trampoline PGD */
> > > >        create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
> > > > @@ -474,7 +578,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> > > >         * whereas dtb_early_va will be used before
> > > > setup_vm_final installs
> > > >         * the linear mapping.
> > > >         */
> > > > -    dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
> > > > +    dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
> > > >    #endif /* CONFIG_BUILTIN_DTB */
> > > >    #else
> > > >    #ifndef CONFIG_BUILTIN_DTB
> > > > @@ -486,7 +590,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> > > >                   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
> > > >        dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa &
> > > > (PGDIR_SIZE - 1));
> > > >    #else /* CONFIG_BUILTIN_DTB */
> > > > -    dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
> > > > +    dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
> > > >    #endif /* CONFIG_BUILTIN_DTB */
> > > >    #endif
> > > >        dtb_early_pa = dtb_pa;
> > > > @@ -522,7 +626,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> > > >    #endif
> > > >    }
> > > > -#ifdef CONFIG_64BIT
> > > > +#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
> > > >    void protect_kernel_linear_mapping_text_rodata(void)
> > > >    {
> > > >        unsigned long text_start = (unsigned long)lm_alias(_start);
> > > > 
> > > 
> > 
> > 
>
David Hildenbrand April 9, 2021, 12:46 p.m. UTC | #6
>>> Also, will that memory properly be exposed in the resource tree as
>>> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
>>> won't work as expected - the kernel won't be included in a dump.
>   
> Do we really need a XIP kernel to included in kdump?
> And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)

See my other mail, maybe we actually want something different.

> 
>> I have just checked and it does not appear in /proc/iomem.
>>
>> Ok your conclusion would be to have struct page, I'm going to implement this
>> version then using memblock as you described.
> 
> I'm not sure this is required. With XIP kernel text never gets into RAM, so
> it does not seem to require struct page.
> 
> XIP by definition has some limitations relatively to "normal" operation,
> so lack of kdump could be one of them.

I agree.

> 
> I might be wrong, but IMHO, artificially creating a memory map for part of
> flash would cause more problems in the long run.

Can you elaborate?

> 
> BTW, how does XIP account the kernel text on other architectures that
> implement it?

Interesting point, I thought XIP would be something new on RISC-V (well, 
at least to me :) ). If that concept exists already, we better mimic 
what existing implementations do.
Alex Ghiti April 9, 2021, 12:57 p.m. UTC | #7
Le 4/9/21 à 8:07 AM, David Hildenbrand a écrit :
> On 09.04.21 13:39, Alex Ghiti wrote:
>> Hi David,
>>
>> Le 4/9/21 à 4:23 AM, David Hildenbrand a écrit :
>>> On 09.04.21 09:14, Alex Ghiti wrote:
>>>> Le 4/9/21 à 2:51 AM, Alexandre Ghiti a écrit :
>>>>> From: Vitaly Wool <vitaly.wool@konsulko.com>
>>>>>
>>>>> 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. 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 for the time being only work on MMU-enabled
>>>>> kernels.
>>>>>
>>>> I added linux-mm and linux-arch to get feedbacks because I noticed that
>>>> DEBUG_VM_PGTABLE fails for SPARSEMEM (it works for FLATMEM but I think
>>>> it does not do what is expected): the fact that we don't have any 
>>>> struct
>>>> page to back the text and rodata in flash is the problem but to which
>>>> extent ?
>>>
>>> Just wondering, why can't we create a memmap for that memory -- or is it
>>> even desireable to not do that explicity? There might be some nasty side
>>> effects when not having a memmap for text and rodata.
>>
>>
>> Do you have examples of such effects ? Any feature that will not work
>> without that ?
>>
> 
> At least if it's not part of /proc/iomem in any way (maybe "System RAM" 
> is not what we want without a memmap, TBD), kexec-tools won't be able to 
> handle it properly e.g., for kdump. But not sure if that is really 
> relevant in your setup.
> 
> Regarding other features, anything that does a pfn_valid(), 
> pfn_to_page() or pfn_to_online_page() would behave differently now -- 
> assuming the kernel doesn't fall into a section with other System RAM 
> (whereby we would still allocate the memmap for the whole section).
> 
> I guess you might stumble over some surprises in some code paths, but 
> nothing really comes to mind. Not sure if your zeropage is part of the 
> kernel image on RISC-V (I remember that we sometimes need a memmap 
> there, but I might be wrong)?


It is in the kernel image and is located in bss which will be in RAM and 
then be backed by a memmap.


> 
> I assume you still somehow create the direct mapping for the kernel, 
> right? So it's really some memory region with a direct mapping but 
> without a memmap (and right now, without a resource), correct?
> 


No I don't create any direct mapping for the text and the rodata.


> [...]
> 
>>>
>>> Also, will that memory properly be exposed in the resource tree as
>>> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
>>> won't work as expected - the kernel won't be included in a dump.
>>
>>
>> I have just checked and it does not appear in /proc/iomem.
>>
>> Ok your conclusion would be to have struct page, I'm going to implement
>> this version then using memblock as you described.
> 
> Let's first evaluate what the harm could be. You could (and should?) 
> create the kernel resource manually - IIRC, that's independent of the 
> memmap/memblock thing.
> 
> @Mike, what's your take on not having a memmap for kernel text and ro data?
>
Mike Rapoport April 9, 2021, 1:59 p.m. UTC | #8
On Fri, Apr 09, 2021 at 02:46:17PM +0200, David Hildenbrand wrote:
> > > > Also, will that memory properly be exposed in the resource tree as
> > > > System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
> > > > won't work as expected - the kernel won't be included in a dump.
> > Do we really need a XIP kernel to included in kdump?
> > And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)
> 
> See my other mail, maybe we actually want something different.
> 
> > 
> > > I have just checked and it does not appear in /proc/iomem.
> > > 
> > > Ok your conclusion would be to have struct page, I'm going to implement this
> > > version then using memblock as you described.
> > 
> > I'm not sure this is required. With XIP kernel text never gets into RAM, so
> > it does not seem to require struct page.
> > 
> > XIP by definition has some limitations relatively to "normal" operation,
> > so lack of kdump could be one of them.
> 
> I agree.
> 
> > 
> > I might be wrong, but IMHO, artificially creating a memory map for part of
> > flash would cause more problems in the long run.
> 
> Can you elaborate?

Nothing particular, just a gut feeling. Usually, when you force something
it comes out the wrong way later.
 
> > 
> > BTW, how does XIP account the kernel text on other architectures that
> > implement it?
> 
> Interesting point, I thought XIP would be something new on RISC-V (well, at
> least to me :) ). If that concept exists already, we better mimic what
> existing implementations do.

I had quick glance at ARM, it seems that kernel text does not have memory
map and does not show up in System RAM.
David Hildenbrand April 9, 2021, 2:10 p.m. UTC | #9
> Am 09.04.2021 um 15:59 schrieb Mike Rapoport <rppt@linux.ibm.com>:
> 
> On Fri, Apr 09, 2021 at 02:46:17PM +0200, David Hildenbrand wrote:
>>>>> Also, will that memory properly be exposed in the resource tree as
>>>>> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
>>>>> won't work as expected - the kernel won't be included in a dump.
>>> Do we really need a XIP kernel to included in kdump?
>>> And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)
>> 
>> See my other mail, maybe we actually want something different.
>> 
>>> 
>>>> I have just checked and it does not appear in /proc/iomem.
>>>> 
>>>> Ok your conclusion would be to have struct page, I'm going to implement this
>>>> version then using memblock as you described.
>>> 
>>> I'm not sure this is required. With XIP kernel text never gets into RAM, so
>>> it does not seem to require struct page.
>>> 
>>> XIP by definition has some limitations relatively to "normal" operation,
>>> so lack of kdump could be one of them.
>> 
>> I agree.
>> 
>>> 
>>> I might be wrong, but IMHO, artificially creating a memory map for part of
>>> flash would cause more problems in the long run.
>> 
>> Can you elaborate?
> 
> Nothing particular, just a gut feeling. Usually, when you force something
> it comes out the wrong way later.
> 
>>> 
>>> BTW, how does XIP account the kernel text on other architectures that
>>> implement it?
>> 
>> Interesting point, I thought XIP would be something new on RISC-V (well, at
>> least to me :) ). If that concept exists already, we better mimic what
>> existing implementations do.
> 
> I had quick glance at ARM, it seems that kernel text does not have memory
> map and does not show up in System RAM.
> 

Does it show up in a different way or not at all?

> -- 
> Sincerely yours,
> Mike.
>
Mike Rapoport April 9, 2021, 2:10 p.m. UTC | #10
On Fri, Apr 09, 2021 at 02:07:24PM +0200, David Hildenbrand wrote:
> On 09.04.21 13:39, Alex Ghiti wrote:
> > Hi David,
> 
> I assume you still somehow create the direct mapping for the kernel, right?
> So it's really some memory region with a direct mapping but without a memmap
> (and right now, without a resource), correct?

XIP kernel text is not a region in memory to begin with ;-)

It resides in a flash and it is executed directly from there without being
relocated to RAM.

That's why it does not need neither direct mapping, nor struct pages.
David Hildenbrand April 9, 2021, 2:16 p.m. UTC | #11
On 09.04.21 16:10, Mike Rapoport wrote:
> On Fri, Apr 09, 2021 at 02:07:24PM +0200, David Hildenbrand wrote:
>> On 09.04.21 13:39, Alex Ghiti wrote:
>>> Hi David,
>>
>> I assume you still somehow create the direct mapping for the kernel, right?
>> So it's really some memory region with a direct mapping but without a memmap
>> (and right now, without a resource), correct?
> 
> XIP kernel text is not a region in memory to begin with ;-)

I think that's the part that confused me. I thought it would be mapped 
somehow into physical address space and would be addressed like other 
memory -- just that reads would be rewired to go to flash.

> 
> It resides in a flash and it is executed directly from there without being
> relocated to RAM.
> 
> That's why it does not need neither direct mapping, nor struct pages.

Thanks for clarifying! :)
Vitaly Wool April 9, 2021, 2:42 p.m. UTC | #12
On Fri, Apr 9, 2021 at 3:59 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
>
> On Fri, Apr 09, 2021 at 02:46:17PM +0200, David Hildenbrand wrote:
> > > > > Also, will that memory properly be exposed in the resource tree as
> > > > > System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
> > > > > won't work as expected - the kernel won't be included in a dump.
> > > Do we really need a XIP kernel to included in kdump?
> > > And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)
> >
> > See my other mail, maybe we actually want something different.
> >
> > >
> > > > I have just checked and it does not appear in /proc/iomem.
> > > >
> > > > Ok your conclusion would be to have struct page, I'm going to implement this
> > > > version then using memblock as you described.
> > >
> > > I'm not sure this is required. With XIP kernel text never gets into RAM, so
> > > it does not seem to require struct page.
> > >
> > > XIP by definition has some limitations relatively to "normal" operation,
> > > so lack of kdump could be one of them.
> >
> > I agree.
> >
> > >
> > > I might be wrong, but IMHO, artificially creating a memory map for part of
> > > flash would cause more problems in the long run.
> >
> > Can you elaborate?
>
> Nothing particular, just a gut feeling. Usually, when you force something
> it comes out the wrong way later.

It's possible still that MTD_XIP is implemented allowing to write to
the flash used for XIP. While flash is being written, memory map
doesn't make sense at all. I can't come up with a real life example
when it can actually lead to problems but it is indeed weird when
System RAM suddenly becomes unreadable. I really don't think exposing
it in /proc/iomem is a good idea.

> > > BTW, how does XIP account the kernel text on other architectures that
> > > implement it?
> >
> > Interesting point, I thought XIP would be something new on RISC-V (well, at
> > least to me :) ). If that concept exists already, we better mimic what
> > existing implementations do.
>
> I had quick glance at ARM, it seems that kernel text does not have memory
> map and does not show up in System RAM.

Exactly, and I believe ARM64 won't do that too when it gets its own
XIP support (which is underway).

Best regards,
   Vitaly
Alex Ghiti April 12, 2021, 5:12 a.m. UTC | #13
Le 4/9/21 à 10:42 AM, Vitaly Wool a écrit :
> On Fri, Apr 9, 2021 at 3:59 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
>>
>> On Fri, Apr 09, 2021 at 02:46:17PM +0200, David Hildenbrand wrote:
>>>>>> Also, will that memory properly be exposed in the resource tree as
>>>>>> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
>>>>>> won't work as expected - the kernel won't be included in a dump.
>>>> Do we really need a XIP kernel to included in kdump?
>>>> And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)
>>>
>>> See my other mail, maybe we actually want something different.
>>>
>>>>
>>>>> I have just checked and it does not appear in /proc/iomem.
>>>>>
>>>>> Ok your conclusion would be to have struct page, I'm going to implement this
>>>>> version then using memblock as you described.
>>>>
>>>> I'm not sure this is required. With XIP kernel text never gets into RAM, so
>>>> it does not seem to require struct page.
>>>>
>>>> XIP by definition has some limitations relatively to "normal" operation,
>>>> so lack of kdump could be one of them.
>>>
>>> I agree.
>>>
>>>>
>>>> I might be wrong, but IMHO, artificially creating a memory map for part of
>>>> flash would cause more problems in the long run.
>>>
>>> Can you elaborate?
>>
>> Nothing particular, just a gut feeling. Usually, when you force something
>> it comes out the wrong way later.
> 
> It's possible still that MTD_XIP is implemented allowing to write to
> the flash used for XIP. While flash is being written, memory map
> doesn't make sense at all. I can't come up with a real life example
> when it can actually lead to problems but it is indeed weird when
> System RAM suddenly becomes unreadable. I really don't think exposing
> it in /proc/iomem is a good idea.
> 
>>>> BTW, how does XIP account the kernel text on other architectures that
>>>> implement it?
>>>
>>> Interesting point, I thought XIP would be something new on RISC-V (well, at
>>> least to me :) ). If that concept exists already, we better mimic what
>>> existing implementations do.
>>
>> I had quick glance at ARM, it seems that kernel text does not have memory
>> map and does not show up in System RAM.
> 
> Exactly, and I believe ARM64 won't do that too when it gets its own
> XIP support (which is underway).
> 


memmap does not seem necessary and ARM/ARM64 do not use it.

But if someone tries to get a struct page from a physical address that 
lies in flash, as mentioned by David, that could lead to silent 
corruptions if something exists at the address where the struct page 
should be. And it is hard to know which features in the kernel depends 
on that.

Regarding SPARSEMEM, the vmemmap lies in its own region so that's 
unlikely to happen, so we will catch those invalid accesses (and that's 
what I observed on riscv).

But for FLATMEM, memmap is in the linear mapping, then that could very 
likely happen silently.

Could a simple solution be to force SPARSEMEM for those XIP kernels ? 
Then wrong things could happen, but we would see those and avoid 
spending hours to debug :)

I will at least send a v8 to remove the pfn_valid modifications for 
FLATMEM that now returns true to pfn in flash.

Thanks,



> Best regards,
>     Vitaly
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
>
Vitaly Wool April 12, 2021, 7:49 a.m. UTC | #14
On Mon, Apr 12, 2021 at 7:12 AM Alex Ghiti <alex@ghiti.fr> wrote:
>
> Le 4/9/21 à 10:42 AM, Vitaly Wool a écrit :
> > On Fri, Apr 9, 2021 at 3:59 PM Mike Rapoport <rppt@linux.ibm.com> wrote:
> >>
> >> On Fri, Apr 09, 2021 at 02:46:17PM +0200, David Hildenbrand wrote:
> >>>>>> Also, will that memory properly be exposed in the resource tree as
> >>>>>> System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore)
> >>>>>> won't work as expected - the kernel won't be included in a dump.
> >>>> Do we really need a XIP kernel to included in kdump?
> >>>> And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-)
> >>>
> >>> See my other mail, maybe we actually want something different.
> >>>
> >>>>
> >>>>> I have just checked and it does not appear in /proc/iomem.
> >>>>>
> >>>>> Ok your conclusion would be to have struct page, I'm going to implement this
> >>>>> version then using memblock as you described.
> >>>>
> >>>> I'm not sure this is required. With XIP kernel text never gets into RAM, so
> >>>> it does not seem to require struct page.
> >>>>
> >>>> XIP by definition has some limitations relatively to "normal" operation,
> >>>> so lack of kdump could be one of them.
> >>>
> >>> I agree.
> >>>
> >>>>
> >>>> I might be wrong, but IMHO, artificially creating a memory map for part of
> >>>> flash would cause more problems in the long run.
> >>>
> >>> Can you elaborate?
> >>
> >> Nothing particular, just a gut feeling. Usually, when you force something
> >> it comes out the wrong way later.
> >
> > It's possible still that MTD_XIP is implemented allowing to write to
> > the flash used for XIP. While flash is being written, memory map
> > doesn't make sense at all. I can't come up with a real life example
> > when it can actually lead to problems but it is indeed weird when
> > System RAM suddenly becomes unreadable. I really don't think exposing
> > it in /proc/iomem is a good idea.
> >
> >>>> BTW, how does XIP account the kernel text on other architectures that
> >>>> implement it?
> >>>
> >>> Interesting point, I thought XIP would be something new on RISC-V (well, at
> >>> least to me :) ). If that concept exists already, we better mimic what
> >>> existing implementations do.
> >>
> >> I had quick glance at ARM, it seems that kernel text does not have memory
> >> map and does not show up in System RAM.
> >
> > Exactly, and I believe ARM64 won't do that too when it gets its own
> > XIP support (which is underway).
> >
>
>
> memmap does not seem necessary and ARM/ARM64 do not use it.
>
> But if someone tries to get a struct page from a physical address that
> lies in flash, as mentioned by David, that could lead to silent
> corruptions if something exists at the address where the struct page
> should be. And it is hard to know which features in the kernel depends
> on that.
>
> Regarding SPARSEMEM, the vmemmap lies in its own region so that's
> unlikely to happen, so we will catch those invalid accesses (and that's
> what I observed on riscv).
>
> But for FLATMEM, memmap is in the linear mapping, then that could very
> likely happen silently.
>
> Could a simple solution be to force SPARSEMEM for those XIP kernels ?
> Then wrong things could happen, but we would see those and avoid
> spending hours to debug :)
>
> I will at least send a v8 to remove the pfn_valid modifications for
> FLATMEM that now returns true to pfn in flash.

That sounds good to me. I am not very keen on spending 200K on struct
pages for flash (we can think of this as of an option but I would
definitely like to have the option to compile it out in the end), so
let's remove pfn_valid and fix things that will eventually break, if
some.

Best regards,
   Vitaly

Patch
diff mbox series

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 8ea60a0a19ae..4d0153805927 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -28,7 +28,7 @@  config RISCV
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SET_DIRECT_MAP
 	select ARCH_HAS_SET_MEMORY
-	select ARCH_HAS_STRICT_KERNEL_RWX if MMU
+	select ARCH_HAS_STRICT_KERNEL_RWX if MMU && !XIP_KERNEL
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
 	select ARCH_OPTIONAL_KERNEL_RWX_DEFAULT
@@ -441,7 +441,7 @@  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
@@ -465,11 +465,56 @@  config STACKPROTECTOR_PER_TASK
 	def_bool y
 	depends on STACKPROTECTOR && CC_HAVE_STACKPROTECTOR_TLS
 
+config PHYS_RAM_BASE_FIXED
+	bool "Explicitly specified physical RAM address"
+	default n
+
+config PHYS_RAM_BASE
+	hex "Platform Physical RAM address"
+	depends on PHYS_RAM_BASE_FIXED
+	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.
+
+config XIP_KERNEL
+	bool "Kernel Execute-In-Place from ROM"
+	depends on MMU
+	select PHYS_RAM_BASE_FIXED
+	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.
+
 endmenu
 
 config BUILTIN_DTB
-	def_bool n
+	bool
 	depends on OF
+	default y if XIP_KERNEL
 
 menu "Power management options"
 
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 1368d943f1f3..8fcbec03974d 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -82,7 +82,11 @@  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
 
@@ -95,12 +99,14 @@  PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
 
+ifneq ($(CONFIG_XIP_KERNEL),y)
 ifeq ($(CONFIG_RISCV_M_MODE)$(CONFIG_SOC_CANAAN),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/page.h b/arch/riscv/include/asm/page.h
index 22cfb2be60dc..6fe0ff8c8fa9 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -91,6 +91,9 @@  typedef struct page *pgtable_t;
 #ifdef CONFIG_MMU
 extern unsigned long va_pa_offset;
 extern unsigned long va_kernel_pa_offset;
+#ifdef CONFIG_XIP_KERNEL
+extern unsigned long va_kernel_xip_pa_offset;
+#endif
 extern unsigned long pfn_base;
 #define ARCH_PFN_OFFSET		(pfn_base)
 #else
@@ -102,11 +105,29 @@  extern unsigned long pfn_base;
 extern unsigned long kernel_virt_addr;
 
 #define linear_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_pa_offset))
+#ifdef CONFIG_XIP_KERNEL
+#define kernel_mapping_pa_to_va(y)	({						\
+	unsigned long _y = y;								\
+	(_y >= CONFIG_PHYS_RAM_BASE) ?							\
+		(void *)((unsigned long)(_y) + va_kernel_pa_offset + XIP_OFFSET) :	\
+		(void *)((unsigned long)(_y) + va_kernel_xip_pa_offset);		\
+	})
+#else
 #define kernel_mapping_pa_to_va(x)	((void *)((unsigned long)(x) + va_kernel_pa_offset))
+#endif
 #define __pa_to_va_nodebug(x)		linear_mapping_pa_to_va(x)
 
 #define linear_mapping_va_to_pa(x)	((unsigned long)(x) - va_pa_offset)
+#ifdef CONFIG_XIP_KERNEL
+#define kernel_mapping_va_to_pa(y) ({						\
+	unsigned long _y = y;							\
+	(_y < kernel_virt_addr + XIP_OFFSET) ?					\
+		((unsigned long)(_y) - va_kernel_xip_pa_offset) :		\
+		((unsigned long)(_y) - va_kernel_pa_offset - XIP_OFFSET);	\
+	})
+#else
 #define kernel_mapping_va_to_pa(x)	((unsigned long)(x) - va_kernel_pa_offset)
+#endif
 #define __va_to_pa_nodebug(x)	({						\
 	unsigned long _x = x;							\
 	(_x < kernel_virt_addr) ?						\
@@ -139,9 +160,16 @@  extern phys_addr_t __phys_addr_symbol(unsigned long x);
 #define phys_to_page(paddr)	(pfn_to_page(phys_to_pfn(paddr)))
 
 #ifdef CONFIG_FLATMEM
+#ifdef CONFIG_XIP_KERNEL
+#define pfn_valid(pfn) \
+	((((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr)) ||	\
+		((pfn) >= PFN_DOWN(CONFIG_XIP_PHYS_ADDR) &&				\
+		(((pfn) - PFN_DOWN(CONFIG_XIP_PHYS_ADDR)) < XIP_OFFSET)))
+#else
 #define pfn_valid(pfn) \
 	(((pfn) >= ARCH_PFN_OFFSET) && (((pfn) - ARCH_PFN_OFFSET) < max_mapnr))
 #endif
+#endif
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 80e63a93e903..c2dc4f83eed8 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -64,6 +64,19 @@ 
 #define FIXADDR_SIZE     PGDIR_SIZE
 #endif
 #define FIXADDR_START    (FIXADDR_TOP - FIXADDR_SIZE)
+
+#ifdef CONFIG_XIP_KERNEL
+#define XIP_OFFSET		SZ_8M
+#define XIP_FIXUP(addr) ({							\
+	uintptr_t __a = (uintptr_t)(addr);					\
+	(__a >= CONFIG_XIP_PHYS_ADDR && __a < CONFIG_XIP_PHYS_ADDR + SZ_16M) ?	\
+		__a - CONFIG_XIP_PHYS_ADDR + CONFIG_PHYS_RAM_BASE - XIP_OFFSET :\
+		__a;								\
+	})
+#else
+#define XIP_FIXUP(addr)		(addr)
+#endif /* CONFIG_XIP_KERNEL */
+
 #endif
 
 #ifndef __ASSEMBLY__
@@ -499,8 +512,16 @@  static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
 #define kern_addr_valid(addr)   (1) /* FIXME */
 
 extern char _start[];
-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);
 void misc_mem_init(void);
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 6cb05f22e52a..89cc58ab52b4 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -9,11 +9,23 @@ 
 #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
+	REG_L t0, _xip_fixup
+	add \reg, \reg, t0
+.endm
+_xip_fixup: .dword CONFIG_PHYS_RAM_BASE - CONFIG_XIP_PHYS_ADDR - XIP_OFFSET
+#else
+.macro XIP_FIXUP_OFFSET reg
+.endm
+#endif /* CONFIG_XIP_KERNEL */
+
 __HEAD
 ENTRY(_start)
 	/*
@@ -70,6 +82,7 @@  pe_head_start:
 relocate:
 	/* Relocate return address */
 	la a1, kernel_virt_addr
+	XIP_FIXUP_OFFSET a1
 	REG_L a1, 0(a1)
 	la a2, _start
 	sub a1, a1, a2
@@ -92,6 +105,7 @@  relocate:
 	 * to ensure the new translations are in use.
 	 */
 	la a0, trampoline_pg_dir
+	XIP_FIXUP_OFFSET a0
 	srl a0, a0, PAGE_SHIFT
 	or a0, a0, a1
 	sfence.vma
@@ -145,7 +159,9 @@  secondary_start_sbi:
 
 	slli a3, a0, LGREG
 	la a4, __cpu_up_stack_pointer
+	XIP_FIXUP_OFFSET a4
 	la a5, __cpu_up_task_pointer
+	XIP_FIXUP_OFFSET a5
 	add a4, a3, a4
 	add a5, a3, a5
 	REG_L sp, (a4)
@@ -157,6 +173,7 @@  secondary_start_common:
 #ifdef CONFIG_MMU
 	/* Enable virtual memory and relocate to virtual address */
 	la a0, swapper_pg_dir
+	XIP_FIXUP_OFFSET a0
 	call relocate
 #endif
 	call setup_trap_vector
@@ -237,12 +254,33 @@  pmp_done:
 .Lgood_cores:
 #endif
 
+#ifndef CONFIG_XIP_KERNEL
 	/* Pick one hart to run the main boot sequence */
 	la a3, hart_lottery
 	li a2, 1
 	amoadd.w a3, a2, (a3)
 	bnez a3, .Lsecondary_start
 
+#else
+	/* hart_lottery in flash contains a magic number */
+	la a3, hart_lottery
+	mv a2, a3
+	XIP_FIXUP_OFFSET a2
+	lw t1, (a3)
+	amoswap.w t0, t1, (a2)
+	/* first time here if hart_lottery in RAM is not set */
+	beq t0, t1, .Lsecondary_start
+
+	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
@@ -252,15 +290,18 @@  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
+	XIP_FIXUP_OFFSET a2
 	REG_S a0, (a2)
 
 	/* Initialize page tables and relocate to virtual addresses */
 	la sp, init_thread_union + THREAD_SIZE
+	XIP_FIXUP_OFFSET sp
 #ifdef CONFIG_BUILTIN_DTB
 	la a0, __dtb_start
 #else
@@ -269,6 +310,7 @@  clear_bss_done:
 	call setup_vm
 #ifdef CONFIG_MMU
 	la a0, early_pg_dir
+	XIP_FIXUP_OFFSET a0
 	call relocate
 #endif /* CONFIG_MMU */
 
@@ -293,7 +335,9 @@  clear_bss_done:
 
 	slli a3, a0, LGREG
 	la a1, __cpu_up_stack_pointer
+	XIP_FIXUP_OFFSET a1
 	la a2, __cpu_up_task_pointer
+	XIP_FIXUP_OFFSET a2
 	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 30e4af0fd50c..2ddf654c72bb 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(0xC001BEEF)
+#endif
+;
 unsigned long boot_cpu_hartid;
 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 
@@ -254,7 +258,7 @@  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(__va(XIP_FIXUP(dtb_early_pa))))
 		unflatten_device_tree();
 	else
 		pr_err("No DTB found in kernel mappings\n");
@@ -266,7 +270,7 @@  void __init setup_arch(char **cmdline_p)
 	if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
 		protect_kernel_text_data();
 
-#if defined(CONFIG_64BIT) && defined(CONFIG_MMU)
+#if defined(CONFIG_64BIT) && defined(CONFIG_MMU) && !defined(CONFIG_XIP_KERNEL)
 	protect_kernel_linear_mapping_text_rodata();
 #endif
 
diff --git a/arch/riscv/kernel/vmlinux-xip.lds.S b/arch/riscv/kernel/vmlinux-xip.lds.S
new file mode 100644
index 000000000000..4b29b9917f99
--- /dev/null
+++ b/arch/riscv/kernel/vmlinux-xip.lds.S
@@ -0,0 +1,133 @@ 
+/* 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
+ */
+
+#include <asm/pgtable.h>
+#define LOAD_OFFSET KERNEL_LINK_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 */
+	. = LOAD_OFFSET;
+	_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 */
+	. = LOAD_OFFSET + XIP_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 0726c05e0336..0a59b65cf789 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -4,8 +4,13 @@ 
  * Copyright (C) 2017 SiFive
  */
 
+#ifdef CONFIG_XIP_KERNEL
+#include "vmlinux-xip.lds.S"
+#else
+
 #include <asm/pgtable.h>
 #define LOAD_OFFSET KERNEL_LINK_ADDR
+
 #include <asm/vmlinux.lds.h>
 #include <asm/page.h>
 #include <asm/cache.h>
@@ -133,3 +138,4 @@  SECTIONS
 
 	DISCARDS
 }
+#endif /* CONFIG_XIP_KERNEL */
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 093f3a96ecfc..9961573f9a55 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -27,6 +27,9 @@ 
 
 unsigned long kernel_virt_addr = KERNEL_LINK_ADDR;
 EXPORT_SYMBOL(kernel_virt_addr);
+#ifdef CONFIG_XIP_KERNEL
+#define kernel_virt_addr       (*((unsigned long *)XIP_FIXUP(&kernel_virt_addr)))
+#endif
 
 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
 							__page_aligned_bss;
@@ -34,8 +37,8 @@  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);
@@ -118,6 +121,10 @@  void __init setup_bootmem(void)
 	phys_addr_t dram_end = memblock_end_of_DRAM();
 	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
 
+#ifdef CONFIG_XIP_KERNEL
+	vmlinux_start = __pa_symbol(&_sdata);
+#endif
+
 	/* The maximal physical memory size is -PAGE_OFFSET. */
 	memblock_enforce_memory_limit(-PAGE_OFFSET);
 
@@ -159,17 +166,44 @@  void __init setup_bootmem(void)
 	memblock_allow_resize();
 }
 
+#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
 
 /* Offset between linear mapping virtual address and kernel load address */
 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
 /* Offset between kernel mapping virtual address and kernel load address */
 unsigned long va_kernel_pa_offset;
 EXPORT_SYMBOL(va_kernel_pa_offset);
+#ifdef CONFIG_XIP_KERNEL
+#define va_kernel_pa_offset    (*((unsigned long *)XIP_FIXUP(&va_kernel_pa_offset)))
+#endif
+unsigned long va_kernel_xip_pa_offset;
+EXPORT_SYMBOL(va_kernel_xip_pa_offset);
+#ifdef CONFIG_XIP_KERNEL
+#define va_kernel_xip_pa_offset        (*((unsigned long *)XIP_FIXUP(&va_kernel_xip_pa_offset)))
+#endif
 unsigned long pfn_base;
 EXPORT_SYMBOL(pfn_base);
+#ifdef CONFIG_XIP_KERNEL
+#define pfn_base       (*((unsigned long *)XIP_FIXUP(&pfn_base)))
+#endif
 
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
 pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
@@ -177,6 +211,12 @@  pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
 
 pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
 
+#ifdef CONFIG_XIP_KERNEL
+#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))
+#endif /* CONFIG_XIP_KERNEL */
+
 void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
 {
 	unsigned long addr = __fix_to_virt(idx);
@@ -252,6 +292,12 @@  pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
 pmd_t early_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
 pmd_t early_dtb_pmd[PTRS_PER_PMD] __initdata __aligned(PAGE_SIZE);
 
+#ifdef CONFIG_XIP_KERNEL
+#define trampoline_pmd ((pmd_t *)XIP_FIXUP(trampoline_pmd))
+#define fixmap_pmd     ((pmd_t *)XIP_FIXUP(fixmap_pmd))
+#define early_pmd      ((pmd_t *)XIP_FIXUP(early_pmd))
+#endif /* CONFIG_XIP_KERNEL */
+
 static pmd_t *__init get_pmd_virt_early(phys_addr_t pa)
 {
 	/* Before MMU is enabled */
@@ -368,6 +414,19 @@  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_PHYS_RAM_BASE;
+	size_t sz = (size_t)(end - from + 1);
+
+	memcpy(to, from, sz);
+}
+#endif
+
 /*
  * setup_vm() is called from head.S with MMU-off.
  *
@@ -387,7 +446,35 @@  static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
 #endif
 
 uintptr_t load_pa, load_sz;
+#ifdef CONFIG_XIP_KERNEL
+#define load_pa        (*((uintptr_t *)XIP_FIXUP(&load_pa)))
+#define load_sz        (*((uintptr_t *)XIP_FIXUP(&load_sz)))
+#endif
+
+#ifdef CONFIG_XIP_KERNEL
+uintptr_t xiprom, xiprom_sz;
+#define xiprom_sz      (*((uintptr_t *)XIP_FIXUP(&xiprom_sz)))
+#define xiprom         (*((uintptr_t *)XIP_FIXUP(&xiprom)))
 
+static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
+{
+	uintptr_t va, end_va;
+
+	/* Map the flash resident part */
+	end_va = kernel_virt_addr + xiprom_sz;
+	for (va = kernel_virt_addr; va < end_va; va += map_size)
+		create_pgd_mapping(pgdir, va,
+				   xiprom + (va - kernel_virt_addr),
+				   map_size, PAGE_KERNEL_EXEC);
+
+	/* Map the data in RAM */
+	end_va = kernel_virt_addr + XIP_OFFSET + load_sz;
+	for (va = kernel_virt_addr + XIP_OFFSET; va < end_va; va += map_size)
+		create_pgd_mapping(pgdir, va,
+				   load_pa + (va - (kernel_virt_addr + XIP_OFFSET)),
+				   map_size, PAGE_KERNEL);
+}
+#else
 static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
 {
 	uintptr_t va, end_va;
@@ -398,16 +485,28 @@  static void __init create_kernel_page_table(pgd_t *pgdir, uintptr_t map_size)
 				   load_pa + (va - kernel_virt_addr),
 				   map_size, PAGE_KERNEL_EXEC);
 }
+#endif
 
 asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 {
-	uintptr_t pa;
+	uintptr_t __maybe_unused pa;
 	uintptr_t map_size;
 #ifndef __PAGETABLE_PMD_FOLDED
 	pmd_t fix_bmap_spmd, fix_bmap_epmd;
 #endif
+
+#ifdef CONFIG_XIP_KERNEL
+	xiprom = (uintptr_t)CONFIG_XIP_PHYS_ADDR;
+	xiprom_sz = (uintptr_t)(&_exiprom) - (uintptr_t)(&_xiprom);
+
+	load_pa = (uintptr_t)CONFIG_PHYS_RAM_BASE;
+	load_sz = (uintptr_t)(&_end) - (uintptr_t)(&_sdata);
+
+	va_kernel_xip_pa_offset = kernel_virt_addr - xiprom;
+#else
 	load_pa = (uintptr_t)(&_start);
 	load_sz = (uintptr_t)(&_end) - load_pa;
+#endif
 
 	va_pa_offset = PAGE_OFFSET - load_pa;
 	va_kernel_pa_offset = kernel_virt_addr - load_pa;
@@ -441,8 +540,13 @@  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	/* Setup trampoline PGD and PMD */
 	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
 			   (uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
+#ifdef CONFIG_XIP_KERNEL
+	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
+			   xiprom, PMD_SIZE, PAGE_KERNEL_EXEC);
+#else
 	create_pmd_mapping(trampoline_pmd, kernel_virt_addr,
 			   load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
+#endif
 #else
 	/* Setup trampoline PGD */
 	create_pgd_mapping(trampoline_pg_dir, kernel_virt_addr,
@@ -474,7 +578,7 @@  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 	 * whereas dtb_early_va will be used before setup_vm_final installs
 	 * the linear mapping.
 	 */
-	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
+	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
 #endif /* CONFIG_BUILTIN_DTB */
 #else
 #ifndef CONFIG_BUILTIN_DTB
@@ -486,7 +590,7 @@  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 			   pa + PGDIR_SIZE, PGDIR_SIZE, PAGE_KERNEL);
 	dtb_early_va = (void *)DTB_EARLY_BASE_VA + (dtb_pa & (PGDIR_SIZE - 1));
 #else /* CONFIG_BUILTIN_DTB */
-	dtb_early_va = kernel_mapping_pa_to_va(dtb_pa);
+	dtb_early_va = kernel_mapping_pa_to_va(XIP_FIXUP(dtb_pa));
 #endif /* CONFIG_BUILTIN_DTB */
 #endif
 	dtb_early_pa = dtb_pa;
@@ -522,7 +626,7 @@  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 #endif
 }
 
-#ifdef CONFIG_64BIT
+#if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
 void protect_kernel_linear_mapping_text_rodata(void)
 {
 	unsigned long text_start = (unsigned long)lm_alias(_start);