[PATCH v6 0/4] RISC-V Hibernation Support

[PATCH v6 0/4] RISC-V Hibernation Support

[Sia Jee Heng]

This series adds RISC-V Hibernation/suspend to disk support.
Low level Arch functions were created to support hibernation.
swsusp_arch_suspend() relies code from __cpu_suspend_enter() to write
cpu state onto the stack, then calling swsusp_save() to save the memory
image.

Arch specific hibernation header is implemented and is utilized by the
arch_hibernation_header_restore() and arch_hibernation_header_save()
functions. The arch specific hibernation header consists of satp, hartid,
and the cpu_resume address. The kernel built version is also need to be
saved into the hibernation image header to making sure only the same
kernel is restore when resume.

swsusp_arch_resume() creates a temporary page table that covering only
the linear map. It copies the restore code to a 'safe' page, then start to
restore the memory image. Once completed, it restores the original
kernel's page table. It then calls into __hibernate_cpu_resume()
to restore the CPU context. Finally, it follows the normal hibernation
path back to the hibernation core.

To enable hibernation/suspend to disk into RISCV, the below config
need to be enabled:
- CONFIG_ARCH_HIBERNATION_HEADER
- CONFIG_ARCH_HIBERNATION_POSSIBLE

At high-level, this series includes the following changes:
1) Change suspend_save_csrs() and suspend_restore_csrs()
   to public function as these functions are common to
   suspend/hibernation. (patch 1)
2) Refactor the common code in the __cpu_resume_enter() function and
   __hibernate_cpu_resume() function. The common code are used by
   hibernation and suspend. (patch 2)
3) Enhance kernel_page_present() function to support huge page. (patch 3)
4) Add arch/riscv low level functions to support
   hibernation/suspend to disk. (patch 4)

The above patches are based on kernel v6.3-rc2 and are tested on
StarFive VF2 SBC board and Qemu. 
ACPI platform mode is not supported in this series.

Changes since v5:
- Rebased to kernel v6.3-rc2
- Removed extra line at the commit msg
- Added comment to describe the reason to map the kernel address

Changes since v4:
- Rebased to kernel v6.3-rc1
- Resolved typo(s)
- Removed unnecessary helper function
- Removed unnecessary "addr" local variable
- Removed typecast of 'int'
- Used def_bool HIBERNATION
- Used "mv a0, zero" instead of "add a0, zero, zero"
- Make linear region as executable and writable when restoring the
  image

Changes since v3:
- Rebased to kernel v6.2
- Temporary page table code refactoring by reference to ARM64
- Resolved typo(s) and grammars
- Resolved documentation errors
- Resolved clang build issue
- Removed unnecessary comments
- Used kzalloc instead of kcalloc

Changes since v2:
- Rebased to kernel v6.2-rc5
- Refactor the common code used by hibernation and suspend
- Create copy_page macro
- Solved other comments from Andrew and Conor

Changes since v1:
- Rebased to kernel v6.2-rc3
- Fixed bot's compilation error

Sia Jee Heng (4):
  RISC-V: Change suspend_save_csrs and suspend_restore_csrs to public
    function
  RISC-V: Factor out common code of __cpu_resume_enter()
  RISC-V: mm: Enable huge page support to kernel_page_present() function
  RISC-V: Add arch functions to support hibernation/suspend-to-disk

 arch/riscv/Kconfig                 |   6 +
 arch/riscv/include/asm/assembler.h |  82 ++++++
 arch/riscv/include/asm/suspend.h   |  22 ++
 arch/riscv/kernel/Makefile         |   1 +
 arch/riscv/kernel/asm-offsets.c    |   5 +
 arch/riscv/kernel/hibernate-asm.S  |  77 ++++++
 arch/riscv/kernel/hibernate.c      | 427 +++++++++++++++++++++++++++++
 arch/riscv/kernel/suspend.c        |   4 +-
 arch/riscv/kernel/suspend_entry.S  |  34 +--
 arch/riscv/mm/pageattr.c           |   8 +
 10 files changed, 633 insertions(+), 33 deletions(-)
 create mode 100644 arch/riscv/include/asm/assembler.h
 create mode 100644 arch/riscv/kernel/hibernate-asm.S
 create mode 100644 arch/riscv/kernel/hibernate.c


base-commit: fc89d7fb499b0162e081f434d45e8d1b47e82ece
-- 
2.34.1


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[PATCH v6 1/4] RISC-V: Change suspend_save_csrs and suspend_restore_csrs to public function

[Sia Jee Heng]

Currently suspend_save_csrs() and suspend_restore_csrs() functions are
statically defined in the suspend.c. Change the function's attribute
to public so that the functions can be used by hibernation as well.

Signed-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
Reviewed-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
Reviewed-by: Mason Huo <mason.huo@starfivetech.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---
 arch/riscv/include/asm/suspend.h | 3 +++
 arch/riscv/kernel/suspend.c      | 4 ++--
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h
index 8be391c2aecb..67e047445662 100644
--- a/arch/riscv/include/asm/suspend.h
+++ b/arch/riscv/include/asm/suspend.h
@@ -33,4 +33,7 @@ int cpu_suspend(unsigned long arg,
 /* Low-level CPU resume entry function */
 int __cpu_resume_enter(unsigned long hartid, unsigned long context);
 
+/* Used to save and restore the CSRs */
+void suspend_save_csrs(struct suspend_context *context);
+void suspend_restore_csrs(struct suspend_context *context);
 #endif
diff --git a/arch/riscv/kernel/suspend.c b/arch/riscv/kernel/suspend.c
index 9ba24fb8cc93..3c89b8ec69c4 100644
--- a/arch/riscv/kernel/suspend.c
+++ b/arch/riscv/kernel/suspend.c
@@ -8,7 +8,7 @@
 #include <asm/csr.h>
 #include <asm/suspend.h>
 
-static void suspend_save_csrs(struct suspend_context *context)
+void suspend_save_csrs(struct suspend_context *context)
 {
 	context->scratch = csr_read(CSR_SCRATCH);
 	context->tvec = csr_read(CSR_TVEC);
@@ -29,7 +29,7 @@ static void suspend_save_csrs(struct suspend_context *context)
 #endif
 }
 
-static void suspend_restore_csrs(struct suspend_context *context)
+void suspend_restore_csrs(struct suspend_context *context)
 {
 	csr_write(CSR_SCRATCH, context->scratch);
 	csr_write(CSR_TVEC, context->tvec);
-- 
2.34.1


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[PATCH v6 2/4] RISC-V: Factor out common code of __cpu_resume_enter()

[Sia Jee Heng]

The cpu_resume() function is very similar for the suspend to disk and
suspend to ram cases. Factor out the common code into suspend_restore_csrs
macro and suspend_restore_regs macro.

Signed-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
---
 arch/riscv/include/asm/assembler.h | 62 ++++++++++++++++++++++++++++++
 arch/riscv/kernel/suspend_entry.S  | 34 ++--------------
 2 files changed, 65 insertions(+), 31 deletions(-)
 create mode 100644 arch/riscv/include/asm/assembler.h

diff --git a/arch/riscv/include/asm/assembler.h b/arch/riscv/include/asm/assembler.h
new file mode 100644
index 000000000000..ba59d38f8937
--- /dev/null
+++ b/arch/riscv/include/asm/assembler.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2023 StarFive Technology Co., Ltd.
+ *
+ * Author: Jee Heng Sia <jeeheng.sia@starfivetech.com>
+ */
+
+#ifndef __ASSEMBLY__
+#error "Only include this from assembly code"
+#endif
+
+#ifndef __ASM_ASSEMBLER_H
+#define __ASM_ASSEMBLER_H
+
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/csr.h>
+
+/*
+ * suspend_restore_csrs - restore CSRs
+ */
+	.macro suspend_restore_csrs
+		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_EPC)(a0)
+		csrw	CSR_EPC, t0
+		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_STATUS)(a0)
+		csrw	CSR_STATUS, t0
+		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_BADADDR)(a0)
+		csrw	CSR_TVAL, t0
+		REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_CAUSE)(a0)
+		csrw	CSR_CAUSE, t0
+	.endm
+
+/*
+ * suspend_restore_regs - Restore registers (except A0 and T0-T6)
+ */
+	.macro suspend_restore_regs
+		REG_L	ra, (SUSPEND_CONTEXT_REGS + PT_RA)(a0)
+		REG_L	sp, (SUSPEND_CONTEXT_REGS + PT_SP)(a0)
+		REG_L	gp, (SUSPEND_CONTEXT_REGS + PT_GP)(a0)
+		REG_L	tp, (SUSPEND_CONTEXT_REGS + PT_TP)(a0)
+		REG_L	s0, (SUSPEND_CONTEXT_REGS + PT_S0)(a0)
+		REG_L	s1, (SUSPEND_CONTEXT_REGS + PT_S1)(a0)
+		REG_L	a1, (SUSPEND_CONTEXT_REGS + PT_A1)(a0)
+		REG_L	a2, (SUSPEND_CONTEXT_REGS + PT_A2)(a0)
+		REG_L	a3, (SUSPEND_CONTEXT_REGS + PT_A3)(a0)
+		REG_L	a4, (SUSPEND_CONTEXT_REGS + PT_A4)(a0)
+		REG_L	a5, (SUSPEND_CONTEXT_REGS + PT_A5)(a0)
+		REG_L	a6, (SUSPEND_CONTEXT_REGS + PT_A6)(a0)
+		REG_L	a7, (SUSPEND_CONTEXT_REGS + PT_A7)(a0)
+		REG_L	s2, (SUSPEND_CONTEXT_REGS + PT_S2)(a0)
+		REG_L	s3, (SUSPEND_CONTEXT_REGS + PT_S3)(a0)
+		REG_L	s4, (SUSPEND_CONTEXT_REGS + PT_S4)(a0)
+		REG_L	s5, (SUSPEND_CONTEXT_REGS + PT_S5)(a0)
+		REG_L	s6, (SUSPEND_CONTEXT_REGS + PT_S6)(a0)
+		REG_L	s7, (SUSPEND_CONTEXT_REGS + PT_S7)(a0)
+		REG_L	s8, (SUSPEND_CONTEXT_REGS + PT_S8)(a0)
+		REG_L	s9, (SUSPEND_CONTEXT_REGS + PT_S9)(a0)
+		REG_L	s10, (SUSPEND_CONTEXT_REGS + PT_S10)(a0)
+		REG_L	s11, (SUSPEND_CONTEXT_REGS + PT_S11)(a0)
+	.endm
+
+#endif	/* __ASM_ASSEMBLER_H */
diff --git a/arch/riscv/kernel/suspend_entry.S b/arch/riscv/kernel/suspend_entry.S
index aafcca58c19d..12b52afe09a4 100644
--- a/arch/riscv/kernel/suspend_entry.S
+++ b/arch/riscv/kernel/suspend_entry.S
@@ -7,6 +7,7 @@
 #include <linux/linkage.h>
 #include <asm/asm.h>
 #include <asm/asm-offsets.h>
+#include <asm/assembler.h>
 #include <asm/csr.h>
 #include <asm/xip_fixup.h>
 
@@ -83,39 +84,10 @@ ENTRY(__cpu_resume_enter)
 	add	a0, a1, zero
 
 	/* Restore CSRs */
-	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_EPC)(a0)
-	csrw	CSR_EPC, t0
-	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_STATUS)(a0)
-	csrw	CSR_STATUS, t0
-	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_BADADDR)(a0)
-	csrw	CSR_TVAL, t0
-	REG_L	t0, (SUSPEND_CONTEXT_REGS + PT_CAUSE)(a0)
-	csrw	CSR_CAUSE, t0
+	suspend_restore_csrs
 
 	/* Restore registers (except A0 and T0-T6) */
-	REG_L	ra, (SUSPEND_CONTEXT_REGS + PT_RA)(a0)
-	REG_L	sp, (SUSPEND_CONTEXT_REGS + PT_SP)(a0)
-	REG_L	gp, (SUSPEND_CONTEXT_REGS + PT_GP)(a0)
-	REG_L	tp, (SUSPEND_CONTEXT_REGS + PT_TP)(a0)
-	REG_L	s0, (SUSPEND_CONTEXT_REGS + PT_S0)(a0)
-	REG_L	s1, (SUSPEND_CONTEXT_REGS + PT_S1)(a0)
-	REG_L	a1, (SUSPEND_CONTEXT_REGS + PT_A1)(a0)
-	REG_L	a2, (SUSPEND_CONTEXT_REGS + PT_A2)(a0)
-	REG_L	a3, (SUSPEND_CONTEXT_REGS + PT_A3)(a0)
-	REG_L	a4, (SUSPEND_CONTEXT_REGS + PT_A4)(a0)
-	REG_L	a5, (SUSPEND_CONTEXT_REGS + PT_A5)(a0)
-	REG_L	a6, (SUSPEND_CONTEXT_REGS + PT_A6)(a0)
-	REG_L	a7, (SUSPEND_CONTEXT_REGS + PT_A7)(a0)
-	REG_L	s2, (SUSPEND_CONTEXT_REGS + PT_S2)(a0)
-	REG_L	s3, (SUSPEND_CONTEXT_REGS + PT_S3)(a0)
-	REG_L	s4, (SUSPEND_CONTEXT_REGS + PT_S4)(a0)
-	REG_L	s5, (SUSPEND_CONTEXT_REGS + PT_S5)(a0)
-	REG_L	s6, (SUSPEND_CONTEXT_REGS + PT_S6)(a0)
-	REG_L	s7, (SUSPEND_CONTEXT_REGS + PT_S7)(a0)
-	REG_L	s8, (SUSPEND_CONTEXT_REGS + PT_S8)(a0)
-	REG_L	s9, (SUSPEND_CONTEXT_REGS + PT_S9)(a0)
-	REG_L	s10, (SUSPEND_CONTEXT_REGS + PT_S10)(a0)
-	REG_L	s11, (SUSPEND_CONTEXT_REGS + PT_S11)(a0)
+	suspend_restore_regs
 
 	/* Return zero value */
 	add	a0, zero, zero
-- 
2.34.1


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[PATCH v6 3/4] RISC-V: mm: Enable huge page support to kernel_page_present() function

[Sia Jee Heng]

Currently kernel_page_present() function doesn't support huge page
detection causes the function to mistakenly return false to the
hibernation core.

Add huge page detection to the function to solve the problem.

Fixes: 9e953cda5cdf ("riscv: Introduce huge page support for 32/64bit kernel")
Signed-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
Reviewed-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
Reviewed-by: Mason Huo <mason.huo@starfivetech.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
---
 arch/riscv/mm/pageattr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/riscv/mm/pageattr.c b/arch/riscv/mm/pageattr.c
index 86c56616e5de..ea3d61de065b 100644
--- a/arch/riscv/mm/pageattr.c
+++ b/arch/riscv/mm/pageattr.c
@@ -217,18 +217,26 @@ bool kernel_page_present(struct page *page)
 	pgd = pgd_offset_k(addr);
 	if (!pgd_present(*pgd))
 		return false;
+	if (pgd_leaf(*pgd))
+		return true;
 
 	p4d = p4d_offset(pgd, addr);
 	if (!p4d_present(*p4d))
 		return false;
+	if (p4d_leaf(*p4d))
+		return true;
 
 	pud = pud_offset(p4d, addr);
 	if (!pud_present(*pud))
 		return false;
+	if (pud_leaf(*pud))
+		return true;
 
 	pmd = pmd_offset(pud, addr);
 	if (!pmd_present(*pmd))
 		return false;
+	if (pmd_leaf(*pmd))
+		return true;
 
 	pte = pte_offset_kernel(pmd, addr);
 	return pte_present(*pte);
-- 
2.34.1


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[PATCH v6 4/4] RISC-V: Add arch functions to support hibernation/suspend-to-disk

[Sia Jee Heng]

Low level Arch functions were created to support hibernation.
swsusp_arch_suspend() relies code from __cpu_suspend_enter() to write
cpu state onto the stack, then calling swsusp_save() to save the memory
image.

Arch specific hibernation header is implemented and is utilized by the
arch_hibernation_header_restore() and arch_hibernation_header_save()
functions. The arch specific hibernation header consists of satp, hartid,
and the cpu_resume address. The kernel built version is also need to be
saved into the hibernation image header to making sure only the same
kernel is restore when resume.

swsusp_arch_resume() creates a temporary page table that covering only
the linear map. It copies the restore code to a 'safe' page, then start
to restore the memory image. Once completed, it restores the original
kernel's page table. It then calls into __hibernate_cpu_resume()
to restore the CPU context. Finally, it follows the normal hibernation
path back to the hibernation core.

To enable hibernation/suspend to disk into RISCV, the below config
need to be enabled:
- CONFIG_ARCH_HIBERNATION_HEADER
- CONFIG_ARCH_HIBERNATION_POSSIBLE

Signed-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
Reviewed-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
Reviewed-by: Mason Huo <mason.huo@starfivetech.com>
---
 arch/riscv/Kconfig                 |   6 +
 arch/riscv/include/asm/assembler.h |  20 ++
 arch/riscv/include/asm/suspend.h   |  19 ++
 arch/riscv/kernel/Makefile         |   1 +
 arch/riscv/kernel/asm-offsets.c    |   5 +
 arch/riscv/kernel/hibernate-asm.S  |  77 ++++++
 arch/riscv/kernel/hibernate.c      | 427 +++++++++++++++++++++++++++++
 7 files changed, 555 insertions(+)
 create mode 100644 arch/riscv/kernel/hibernate-asm.S
 create mode 100644 arch/riscv/kernel/hibernate.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c5e42cc37604..473c2a1a6884 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -707,6 +707,12 @@ menu "Power management options"
 
 source "kernel/power/Kconfig"
 
+config ARCH_HIBERNATION_POSSIBLE
+	def_bool y
+
+config ARCH_HIBERNATION_HEADER
+	def_bool HIBERNATION
+
 endmenu # "Power management options"
 
 menu "CPU Power Management"
diff --git a/arch/riscv/include/asm/assembler.h b/arch/riscv/include/asm/assembler.h
index ba59d38f8937..44b1457d3e95 100644
--- a/arch/riscv/include/asm/assembler.h
+++ b/arch/riscv/include/asm/assembler.h
@@ -59,4 +59,24 @@
 		REG_L	s11, (SUSPEND_CONTEXT_REGS + PT_S11)(a0)
 	.endm
 
+/*
+ * copy_page - copy 1 page (4KB) of data from source to destination
+ * @a0 - destination
+ * @a1 - source
+ */
+	.macro	copy_page a0, a1
+		lui	a2, 0x1
+		add	a2, a2, a0
+1 :
+		REG_L	t0, 0(a1)
+		REG_L	t1, SZREG(a1)
+
+		REG_S	t0, 0(a0)
+		REG_S	t1, SZREG(a0)
+
+		addi	a0, a0, 2 * SZREG
+		addi	a1, a1, 2 * SZREG
+		bne	a2, a0, 1b
+	.endm
+
 #endif	/* __ASM_ASSEMBLER_H */
diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h
index 67e047445662..02f87867389a 100644
--- a/arch/riscv/include/asm/suspend.h
+++ b/arch/riscv/include/asm/suspend.h
@@ -21,6 +21,11 @@ struct suspend_context {
 #endif
 };
 
+/*
+ * Used by hibernation core and cleared during resume sequence
+ */
+extern int in_suspend;
+
 /* Low-level CPU suspend entry function */
 int __cpu_suspend_enter(struct suspend_context *context);
 
@@ -36,4 +41,18 @@ int __cpu_resume_enter(unsigned long hartid, unsigned long context);
 /* Used to save and restore the CSRs */
 void suspend_save_csrs(struct suspend_context *context);
 void suspend_restore_csrs(struct suspend_context *context);
+
+/* Low-level API to support hibernation */
+int swsusp_arch_suspend(void);
+int swsusp_arch_resume(void);
+int arch_hibernation_header_save(void *addr, unsigned int max_size);
+int arch_hibernation_header_restore(void *addr);
+int __hibernate_cpu_resume(void);
+
+/* Used to resume on the CPU we hibernated on */
+int hibernate_resume_nonboot_cpu_disable(void);
+
+asmlinkage void hibernate_restore_image(unsigned long resume_satp, unsigned long satp_temp,
+					unsigned long cpu_resume);
+asmlinkage int hibernate_core_restore_code(void);
 #endif
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 4cf303a779ab..daab341d55e4 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -64,6 +64,7 @@ obj-$(CONFIG_MODULES)		+= module.o
 obj-$(CONFIG_MODULE_SECTIONS)	+= module-sections.o
 
 obj-$(CONFIG_CPU_PM)		+= suspend_entry.o suspend.o
+obj-$(CONFIG_HIBERNATION)	+= hibernate.o hibernate-asm.o
 
 obj-$(CONFIG_FUNCTION_TRACER)	+= mcount.o ftrace.o
 obj-$(CONFIG_DYNAMIC_FTRACE)	+= mcount-dyn.o
diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index df9444397908..d6a75aac1d27 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -9,6 +9,7 @@
 #include <linux/kbuild.h>
 #include <linux/mm.h>
 #include <linux/sched.h>
+#include <linux/suspend.h>
 #include <asm/kvm_host.h>
 #include <asm/thread_info.h>
 #include <asm/ptrace.h>
@@ -116,6 +117,10 @@ void asm_offsets(void)
 
 	OFFSET(SUSPEND_CONTEXT_REGS, suspend_context, regs);
 
+	OFFSET(HIBERN_PBE_ADDR, pbe, address);
+	OFFSET(HIBERN_PBE_ORIG, pbe, orig_address);
+	OFFSET(HIBERN_PBE_NEXT, pbe, next);
+
 	OFFSET(KVM_ARCH_GUEST_ZERO, kvm_vcpu_arch, guest_context.zero);
 	OFFSET(KVM_ARCH_GUEST_RA, kvm_vcpu_arch, guest_context.ra);
 	OFFSET(KVM_ARCH_GUEST_SP, kvm_vcpu_arch, guest_context.sp);
diff --git a/arch/riscv/kernel/hibernate-asm.S b/arch/riscv/kernel/hibernate-asm.S
new file mode 100644
index 000000000000..effaf5ca5da0
--- /dev/null
+++ b/arch/riscv/kernel/hibernate-asm.S
@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Hibernation low level support for RISCV.
+ *
+ * Copyright (C) 2023 StarFive Technology Co., Ltd.
+ *
+ * Author: Jee Heng Sia <jeeheng.sia@starfivetech.com>
+ */
+
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/assembler.h>
+#include <asm/csr.h>
+
+#include <linux/linkage.h>
+
+/*
+ * int __hibernate_cpu_resume(void)
+ * Switch back to the hibernated image's page table prior to restoring the CPU
+ * context.
+ *
+ * Always returns 0
+ */
+ENTRY(__hibernate_cpu_resume)
+	/* switch to hibernated image's page table. */
+	csrw CSR_SATP, s0
+	sfence.vma
+
+	REG_L	a0, hibernate_cpu_context
+
+	suspend_restore_csrs
+	suspend_restore_regs
+
+	/* Return zero value. */
+	mv	a0, zero
+
+	ret
+END(__hibernate_cpu_resume)
+
+/*
+ * Prepare to restore the image.
+ * a0: satp of saved page tables.
+ * a1: satp of temporary page tables.
+ * a2: cpu_resume.
+ */
+ENTRY(hibernate_restore_image)
+	mv	s0, a0
+	mv	s1, a1
+	mv	s2, a2
+	REG_L	s4, restore_pblist
+	REG_L	a1, relocated_restore_code
+
+	jalr	a1
+END(hibernate_restore_image)
+
+/*
+ * The below code will be executed from a 'safe' page.
+ * It first switches to the temporary page table, then starts to copy the pages
+ * back to the original memory location. Finally, it jumps to __hibernate_cpu_resume()
+ * to restore the CPU context.
+ */
+ENTRY(hibernate_core_restore_code)
+	/* switch to temp page table. */
+	csrw satp, s1
+	sfence.vma
+.Lcopy:
+	/* The below code will restore the hibernated image. */
+	REG_L	a1, HIBERN_PBE_ADDR(s4)
+	REG_L	a0, HIBERN_PBE_ORIG(s4)
+
+	copy_page a0, a1
+
+	REG_L	s4, HIBERN_PBE_NEXT(s4)
+	bnez	s4, .Lcopy
+
+	jalr	s2
+END(hibernate_core_restore_code)
diff --git a/arch/riscv/kernel/hibernate.c b/arch/riscv/kernel/hibernate.c
new file mode 100644
index 000000000000..f11be60b0668
--- /dev/null
+++ b/arch/riscv/kernel/hibernate.c
@@ -0,0 +1,427 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Hibernation support for RISCV
+ *
+ * Copyright (C) 2023 StarFive Technology Co., Ltd.
+ *
+ * Author: Jee Heng Sia <jeeheng.sia@starfivetech.com>
+ */
+
+#include <asm/barrier.h>
+#include <asm/cacheflush.h>
+#include <asm/mmu_context.h>
+#include <asm/page.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+#include <asm/sections.h>
+#include <asm/set_memory.h>
+#include <asm/smp.h>
+#include <asm/suspend.h>
+
+#include <linux/cpu.h>
+#include <linux/memblock.h>
+#include <linux/pm.h>
+#include <linux/sched.h>
+#include <linux/suspend.h>
+#include <linux/utsname.h>
+
+/* The logical cpu number we should resume on, initialised to a non-cpu number. */
+static int sleep_cpu = -EINVAL;
+
+/* Pointer to the temporary resume page table. */
+static pgd_t *resume_pg_dir;
+
+/* CPU context to be saved. */
+struct suspend_context *hibernate_cpu_context;
+EXPORT_SYMBOL_GPL(hibernate_cpu_context);
+
+unsigned long relocated_restore_code;
+EXPORT_SYMBOL_GPL(relocated_restore_code);
+
+/**
+ * struct arch_hibernate_hdr_invariants - container to store kernel build version.
+ * @uts_version: to save the build number and date so that the we do not resume with
+ *		a different kernel.
+ */
+struct arch_hibernate_hdr_invariants {
+	char		uts_version[__NEW_UTS_LEN + 1];
+};
+
+/**
+ * struct arch_hibernate_hdr - helper parameters that help us to restore the image.
+ * @invariants: container to store kernel build version.
+ * @hartid: to make sure same boot_cpu executes the hibernate/restore code.
+ * @saved_satp: original page table used by the hibernated image.
+ * @restore_cpu_addr: the kernel's image address to restore the CPU context.
+ */
+static struct arch_hibernate_hdr {
+	struct arch_hibernate_hdr_invariants invariants;
+	unsigned long	hartid;
+	unsigned long	saved_satp;
+	unsigned long	restore_cpu_addr;
+} resume_hdr;
+
+static void arch_hdr_invariants(struct arch_hibernate_hdr_invariants *i)
+{
+	memset(i, 0, sizeof(*i));
+	memcpy(i->uts_version, init_utsname()->version, sizeof(i->uts_version));
+}
+
+/*
+ * Check if the given pfn is in the 'nosave' section.
+ */
+int pfn_is_nosave(unsigned long pfn)
+{
+	unsigned long nosave_begin_pfn = sym_to_pfn(&__nosave_begin);
+	unsigned long nosave_end_pfn = sym_to_pfn(&__nosave_end - 1);
+
+	return ((pfn >= nosave_begin_pfn) && (pfn <= nosave_end_pfn));
+}
+
+void notrace save_processor_state(void)
+{
+	WARN_ON(num_online_cpus() != 1);
+}
+
+void notrace restore_processor_state(void)
+{
+}
+
+/*
+ * Helper parameters need to be saved to the hibernation image header.
+ */
+int arch_hibernation_header_save(void *addr, unsigned int max_size)
+{
+	struct arch_hibernate_hdr *hdr = addr;
+
+	if (max_size < sizeof(*hdr))
+		return -EOVERFLOW;
+
+	arch_hdr_invariants(&hdr->invariants);
+
+	hdr->hartid = cpuid_to_hartid_map(sleep_cpu);
+	hdr->saved_satp = csr_read(CSR_SATP);
+	hdr->restore_cpu_addr = (unsigned long)__hibernate_cpu_resume;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(arch_hibernation_header_save);
+
+/*
+ * Retrieve the helper parameters from the hibernation image header.
+ */
+int arch_hibernation_header_restore(void *addr)
+{
+	struct arch_hibernate_hdr_invariants invariants;
+	struct arch_hibernate_hdr *hdr = addr;
+	int ret = 0;
+
+	arch_hdr_invariants(&invariants);
+
+	if (memcmp(&hdr->invariants, &invariants, sizeof(invariants))) {
+		pr_crit("Hibernate image not generated by this kernel!\n");
+		return -EINVAL;
+	}
+
+	sleep_cpu = riscv_hartid_to_cpuid(hdr->hartid);
+	if (sleep_cpu < 0) {
+		pr_crit("Hibernated on a CPU not known to this kernel!\n");
+		sleep_cpu = -EINVAL;
+		return -EINVAL;
+	}
+
+#ifdef CONFIG_SMP
+	ret = bringup_hibernate_cpu(sleep_cpu);
+	if (ret) {
+		sleep_cpu = -EINVAL;
+		return ret;
+	}
+#endif
+	resume_hdr = *hdr;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(arch_hibernation_header_restore);
+
+int swsusp_arch_suspend(void)
+{
+	int ret = 0;
+
+	if (__cpu_suspend_enter(hibernate_cpu_context)) {
+		sleep_cpu = smp_processor_id();
+		suspend_save_csrs(hibernate_cpu_context);
+		ret = swsusp_save();
+	} else {
+		suspend_restore_csrs(hibernate_cpu_context);
+		flush_tlb_all();
+		flush_icache_all();
+
+		/*
+		 * Tell the hibernation core that we've just restored the memory.
+		 */
+		in_suspend = 0;
+		sleep_cpu = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int temp_pgtable_map_pte(pmd_t *dst_pmdp, pmd_t *src_pmdp, unsigned long start,
+				unsigned long end, pgprot_t prot)
+{
+	pte_t *src_ptep;
+	pte_t *dst_ptep;
+
+	if (pmd_none(READ_ONCE(*dst_pmdp))) {
+		dst_ptep = (pte_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_ptep)
+			return -ENOMEM;
+
+		pmd_populate_kernel(NULL, dst_pmdp, dst_ptep);
+	}
+
+	dst_ptep = pte_offset_kernel(dst_pmdp, start);
+	src_ptep = pte_offset_kernel(src_pmdp, start);
+
+	do {
+		pte_t pte = READ_ONCE(*src_ptep);
+
+		if (pte_present(pte))
+			set_pte(dst_ptep, __pte(pte_val(pte) | pgprot_val(prot)));
+	} while (dst_ptep++, src_ptep++, start += PAGE_SIZE, start < end);
+
+	return 0;
+}
+
+static int temp_pgtable_map_pmd(pud_t *dst_pudp, pud_t *src_pudp, unsigned long start,
+				unsigned long end, pgprot_t prot)
+{
+	unsigned long next;
+	unsigned long ret;
+	pmd_t *src_pmdp;
+	pmd_t *dst_pmdp;
+
+	if (pud_none(READ_ONCE(*dst_pudp))) {
+		dst_pmdp = (pmd_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_pmdp)
+			return -ENOMEM;
+
+		pud_populate(NULL, dst_pudp, dst_pmdp);
+	}
+
+	dst_pmdp = pmd_offset(dst_pudp, start);
+	src_pmdp = pmd_offset(src_pudp, start);
+
+	do {
+		pmd_t pmd = READ_ONCE(*src_pmdp);
+
+		next = pmd_addr_end(start, end);
+
+		if (pmd_none(pmd))
+			continue;
+
+		if (pmd_leaf(pmd)) {
+			set_pmd(dst_pmdp, __pmd(pmd_val(pmd) | pgprot_val(prot)));
+		} else {
+			ret = temp_pgtable_map_pte(dst_pmdp, src_pmdp, start, next, prot);
+			if (ret)
+				return -ENOMEM;
+		}
+	} while (dst_pmdp++, src_pmdp++, start = next, start != end);
+
+	return 0;
+}
+
+static int temp_pgtable_map_pud(p4d_t *dst_p4dp, p4d_t *src_p4dp, unsigned long start,
+				unsigned long end, pgprot_t prot)
+{
+	unsigned long next;
+	unsigned long ret;
+	pud_t *dst_pudp;
+	pud_t *src_pudp;
+
+	if (p4d_none(READ_ONCE(*dst_p4dp))) {
+		dst_pudp = (pud_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_pudp)
+			return -ENOMEM;
+
+		p4d_populate(NULL, dst_p4dp, dst_pudp);
+	}
+
+	dst_pudp = pud_offset(dst_p4dp, start);
+	src_pudp = pud_offset(src_p4dp, start);
+
+	do {
+		pud_t pud = READ_ONCE(*src_pudp);
+
+		next = pud_addr_end(start, end);
+
+		if (pud_none(pud))
+			continue;
+
+		if (pud_leaf(pud)) {
+			set_pud(dst_pudp, __pud(pud_val(pud) | pgprot_val(prot)));
+		} else {
+			ret = temp_pgtable_map_pmd(dst_pudp, src_pudp, start, next, prot);
+			if (ret)
+				return -ENOMEM;
+		}
+	} while (dst_pudp++, src_pudp++, start = next, start != end);
+
+	return 0;
+}
+
+static int temp_pgtable_map_p4d(pgd_t *dst_pgdp, pgd_t *src_pgdp, unsigned long start,
+				unsigned long end, pgprot_t prot)
+{
+	unsigned long next;
+	unsigned long ret;
+	p4d_t *dst_p4dp;
+	p4d_t *src_p4dp;
+
+	if (pgd_none(READ_ONCE(*dst_pgdp))) {
+		dst_p4dp = (p4d_t *)get_safe_page(GFP_ATOMIC);
+		if (!dst_p4dp)
+			return -ENOMEM;
+
+		pgd_populate(NULL, dst_pgdp, dst_p4dp);
+	}
+
+	dst_p4dp = p4d_offset(dst_pgdp, start);
+	src_p4dp = p4d_offset(src_pgdp, start);
+
+	do {
+		p4d_t p4d = READ_ONCE(*src_p4dp);
+
+		next = p4d_addr_end(start, end);
+
+		if (p4d_none(p4d))
+			continue;
+
+		if (p4d_leaf(p4d)) {
+			set_p4d(dst_p4dp, __p4d(p4d_val(p4d) | pgprot_val(prot)));
+		} else {
+			ret = temp_pgtable_map_pud(dst_p4dp, src_p4dp, start, next, prot);
+			if (ret)
+				return -ENOMEM;
+		}
+	} while (dst_p4dp++, src_p4dp++, start = next, start != end);
+
+	return 0;
+}
+
+static int temp_pgtable_mapping(pgd_t *pgdp, unsigned long start, unsigned long end, pgprot_t prot)
+{
+	pgd_t *dst_pgdp = pgd_offset_pgd(pgdp, start);
+	pgd_t *src_pgdp = pgd_offset_k(start);
+	unsigned long next;
+	unsigned long ret;
+
+	do {
+		pgd_t pgd = READ_ONCE(*src_pgdp);
+
+		next = pgd_addr_end(start, end);
+
+		if (pgd_none(pgd))
+			continue;
+
+		if (pgd_leaf(pgd)) {
+			set_pgd(dst_pgdp, __pgd(pgd_val(pgd) | pgprot_val(prot)));
+		} else {
+			ret = temp_pgtable_map_p4d(dst_pgdp, src_pgdp, start, next, prot);
+			if (ret)
+				return -ENOMEM;
+		}
+	} while (dst_pgdp++, src_pgdp++, start = next, start != end);
+
+	return 0;
+}
+
+static unsigned long relocate_restore_code(void)
+{
+	void *page = (void *)get_safe_page(GFP_ATOMIC);
+
+	if (!page)
+		return -ENOMEM;
+
+	copy_page(page, hibernate_core_restore_code);
+
+	/* Make the page containing the relocated code executable. */
+	set_memory_x((unsigned long)page, 1);
+
+	return (unsigned long)page;
+}
+
+int swsusp_arch_resume(void)
+{
+	unsigned long end = (unsigned long)pfn_to_virt(max_low_pfn);
+	unsigned long start = PAGE_OFFSET;
+	int ret;
+
+	/*
+	 * Memory allocated by get_safe_page() will be dealt with by the hibernation core,
+	 * we don't need to free it here.
+	 */
+	resume_pg_dir = (pgd_t *)get_safe_page(GFP_ATOMIC);
+	if (!resume_pg_dir)
+		return -ENOMEM;
+
+	/*
+	 * Create a temporary page table and map the whole linear region as executable and
+	 * writable.
+	 */
+	ret = temp_pgtable_mapping(resume_pg_dir, start, end, __pgprot(_PAGE_WRITE | _PAGE_EXEC));
+	if (ret)
+		return ret;
+
+	/* Move the restore code to a new page so that it doesn't get overwritten by itself. */
+	relocated_restore_code = relocate_restore_code();
+	if (relocated_restore_code == -ENOMEM)
+		return -ENOMEM;
+
+	/*
+	 * Map the __hibernate_cpu_resume() address to the temporary page table so that the
+	 * restore code can jumps to it after finished restore the image. The next execution
+	 * code doesn't find itself in a different address space after switching over to the
+	 * original page table used by the hibernated image.
+	 * The __hibernate_cpu_resume() mapping is unnecessary for RV32 since the kernel and
+	 * linear addresses are identical, but different for RV64. To ensure consistency, we
+	 * map it for both RV32 and RV64 kernels.
+	 * Additionally, we should ensure that the page is writable before restoring the image.
+	 */
+	start = (unsigned long)resume_hdr.restore_cpu_addr;
+	end = start + PAGE_SIZE;
+
+	ret = temp_pgtable_mapping(resume_pg_dir, start, end, __pgprot(_PAGE_WRITE));
+	if (ret)
+		return ret;
+
+	hibernate_restore_image(resume_hdr.saved_satp, (PFN_DOWN(__pa(resume_pg_dir)) | satp_mode),
+				resume_hdr.restore_cpu_addr);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP_SMP
+int hibernate_resume_nonboot_cpu_disable(void)
+{
+	if (sleep_cpu < 0) {
+		pr_err("Failing to resume from hibernate on an unknown CPU\n");
+		return -ENODEV;
+	}
+
+	return freeze_secondary_cpus(sleep_cpu);
+}
+#endif
+
+static int __init riscv_hibernate_init(void)
+{
+	hibernate_cpu_context = kzalloc(sizeof(*hibernate_cpu_context), GFP_KERNEL);
+
+	if (WARN_ON(!hibernate_cpu_context))
+		return -ENOMEM;
+
+	return 0;
+}
+
+early_initcall(riscv_hibernate_init);
-- 
2.34.1


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RE: [PATCH v6 0/4] RISC-V Hibernation Support

[JeeHeng Sia]

Hi,

I understand that you must be extremely busy, but I was wondering if there are any comments for the below v6 patch series?

Thanks
Regards
Jee Heng

> -----Original Message-----
> From: JeeHeng Sia <jeeheng.sia@starfivetech.com>
> Sent: Tuesday, March 14, 2023 1:03 PM
> To: paul.walmsley@sifive.com; palmer@dabbelt.com; aou@eecs.berkeley.edu
> Cc: linux-riscv@lists.infradead.org; linux-kernel@vger.kernel.org; JeeHeng Sia <jeeheng.sia@starfivetech.com>; Leyfoon Tan
> <leyfoon.tan@starfivetech.com>; Mason Huo <mason.huo@starfivetech.com>
> Subject: [PATCH v6 0/4] RISC-V Hibernation Support
> 
> This series adds RISC-V Hibernation/suspend to disk support.
> Low level Arch functions were created to support hibernation.
> swsusp_arch_suspend() relies code from __cpu_suspend_enter() to write
> cpu state onto the stack, then calling swsusp_save() to save the memory
> image.
> 
> Arch specific hibernation header is implemented and is utilized by the
> arch_hibernation_header_restore() and arch_hibernation_header_save()
> functions. The arch specific hibernation header consists of satp, hartid,
> and the cpu_resume address. The kernel built version is also need to be
> saved into the hibernation image header to making sure only the same
> kernel is restore when resume.
> 
> swsusp_arch_resume() creates a temporary page table that covering only
> the linear map. It copies the restore code to a 'safe' page, then start to
> restore the memory image. Once completed, it restores the original
> kernel's page table. It then calls into __hibernate_cpu_resume()
> to restore the CPU context. Finally, it follows the normal hibernation
> path back to the hibernation core.
> 
> To enable hibernation/suspend to disk into RISCV, the below config
> need to be enabled:
> - CONFIG_ARCH_HIBERNATION_HEADER
> - CONFIG_ARCH_HIBERNATION_POSSIBLE
> 
> At high-level, this series includes the following changes:
> 1) Change suspend_save_csrs() and suspend_restore_csrs()
>    to public function as these functions are common to
>    suspend/hibernation. (patch 1)
> 2) Refactor the common code in the __cpu_resume_enter() function and
>    __hibernate_cpu_resume() function. The common code are used by
>    hibernation and suspend. (patch 2)
> 3) Enhance kernel_page_present() function to support huge page. (patch 3)
> 4) Add arch/riscv low level functions to support
>    hibernation/suspend to disk. (patch 4)
> 
> The above patches are based on kernel v6.3-rc2 and are tested on
> StarFive VF2 SBC board and Qemu.
> ACPI platform mode is not supported in this series.
> 
> Changes since v5:
> - Rebased to kernel v6.3-rc2
> - Removed extra line at the commit msg
> - Added comment to describe the reason to map the kernel address
> 
> Changes since v4:
> - Rebased to kernel v6.3-rc1
> - Resolved typo(s)
> - Removed unnecessary helper function
> - Removed unnecessary "addr" local variable
> - Removed typecast of 'int'
> - Used def_bool HIBERNATION
> - Used "mv a0, zero" instead of "add a0, zero, zero"
> - Make linear region as executable and writable when restoring the
>   image
> 
> Changes since v3:
> - Rebased to kernel v6.2
> - Temporary page table code refactoring by reference to ARM64
> - Resolved typo(s) and grammars
> - Resolved documentation errors
> - Resolved clang build issue
> - Removed unnecessary comments
> - Used kzalloc instead of kcalloc
> 
> Changes since v2:
> - Rebased to kernel v6.2-rc5
> - Refactor the common code used by hibernation and suspend
> - Create copy_page macro
> - Solved other comments from Andrew and Conor
> 
> Changes since v1:
> - Rebased to kernel v6.2-rc3
> - Fixed bot's compilation error
> 
> Sia Jee Heng (4):
>   RISC-V: Change suspend_save_csrs and suspend_restore_csrs to public
>     function
>   RISC-V: Factor out common code of __cpu_resume_enter()
>   RISC-V: mm: Enable huge page support to kernel_page_present() function
>   RISC-V: Add arch functions to support hibernation/suspend-to-disk
> 
>  arch/riscv/Kconfig                 |   6 +
>  arch/riscv/include/asm/assembler.h |  82 ++++++
>  arch/riscv/include/asm/suspend.h   |  22 ++
>  arch/riscv/kernel/Makefile         |   1 +
>  arch/riscv/kernel/asm-offsets.c    |   5 +
>  arch/riscv/kernel/hibernate-asm.S  |  77 ++++++
>  arch/riscv/kernel/hibernate.c      | 427 +++++++++++++++++++++++++++++
>  arch/riscv/kernel/suspend.c        |   4 +-
>  arch/riscv/kernel/suspend_entry.S  |  34 +--
>  arch/riscv/mm/pageattr.c           |   8 +
>  10 files changed, 633 insertions(+), 33 deletions(-)
>  create mode 100644 arch/riscv/include/asm/assembler.h
>  create mode 100644 arch/riscv/kernel/hibernate-asm.S
>  create mode 100644 arch/riscv/kernel/hibernate.c
> 
> 
> base-commit: fc89d7fb499b0162e081f434d45e8d1b47e82ece
> --
> 2.34.1


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Re: [PATCH v6 0/4] RISC-V Hibernation Support

[Conor Dooley]

[-- Attachment #1.1: Type: text/plain, Size: 326 bytes --]

On Mon, Mar 20, 2023 at 07:20:58AM +0000, JeeHeng Sia wrote:
> Hi,
> 
> I understand that you must be extremely busy, but I was wondering if
> there are any comments for the below v6 patch series?

> > -----Original Message-----
> > Sent: Tuesday, March 14, 2023 1:03 PM

It's not even been a week chief, relax :)


[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

[-- Attachment #2: Type: text/plain, Size: 161 bytes --]

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Re: [PATCH v6 2/4] RISC-V: Factor out common code of __cpu_resume_enter()

[Conor Dooley]

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Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

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Re: [PATCH v6 4/4] RISC-V: Add arch functions to support hibernation/suspend-to-disk

[Conor Dooley]

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On Tue, Mar 14, 2023 at 01:03:16PM +0800, Sia Jee Heng wrote:
> Low level Arch functions were created to support hibernation.
> swsusp_arch_suspend() relies code from __cpu_suspend_enter() to write
> cpu state onto the stack, then calling swsusp_save() to save the memory
> image.
> 
> Arch specific hibernation header is implemented and is utilized by the
> arch_hibernation_header_restore() and arch_hibernation_header_save()
> functions. The arch specific hibernation header consists of satp, hartid,
> and the cpu_resume address. The kernel built version is also need to be
> saved into the hibernation image header to making sure only the same
> kernel is restore when resume.
> 
> swsusp_arch_resume() creates a temporary page table that covering only
> the linear map. It copies the restore code to a 'safe' page, then start
> to restore the memory image. Once completed, it restores the original
> kernel's page table. It then calls into __hibernate_cpu_resume()
> to restore the CPU context. Finally, it follows the normal hibernation
> path back to the hibernation core.
> 
> To enable hibernation/suspend to disk into RISCV, the below config
> need to be enabled:
> - CONFIG_ARCH_HIBERNATION_HEADER
> - CONFIG_ARCH_HIBERNATION_POSSIBLE
> 
> Signed-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
> Reviewed-by: Ley Foon Tan <leyfoon.tan@starfivetech.com>
> Reviewed-by: Mason Huo <mason.huo@starfivetech.com>

> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index c5e42cc37604..473c2a1a6884 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -707,6 +707,12 @@  menu "Power management options"
>  
>  source "kernel/power/Kconfig"
>  
> +config ARCH_HIBERNATION_POSSIBLE
> +	def_bool y
> +
> +config ARCH_HIBERNATION_HEADER
> +	def_bool HIBERNATION
> +
>  endmenu # "Power management options"
>  
>  menu "CPU Power Management"

Since these options are not user-selectable, how come these are
def_bools, rather than just selecting them in the main `config RISCV`
section? Is there some sort of dependency that goes wrong when
structured that way?

> diff --git a/arch/riscv/kernel/hibernate.c b/arch/riscv/kernel/hibernate.c
> new file mode 100644
> index 000000000000..f11be60b0668
> --- /dev/null
> +++ b/arch/riscv/kernel/hibernate.c

> +/**
> + * struct arch_hibernate_hdr_invariants - container to store kernel build version.
> + * @uts_version: to save the build number and date so that the we do not resume with

nit: s/so that the we/so that we/

I noted previously that the page table stuff is beyond me, so modulo
that, I'm happy with how this looks now.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Thanks for adding hibernation support!
Conor.

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