[PATCH v3 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@xxxxxxxxxxxxxxxx>
Reviewed-by: Ley Foon Tan <leyfoon.tan@xxxxxxxxxxxxxxxx>
Reviewed-by: Mason Huo <mason.huo@xxxxxxxxxxxxxxxx>
---
 arch/riscv/Kconfig                 |   7 +
 arch/riscv/include/asm/assembler.h |  20 ++
 arch/riscv/include/asm/suspend.h   |  21 ++
 arch/riscv/kernel/Makefile         |   1 +
 arch/riscv/kernel/asm-offsets.c    |   5 +
 arch/riscv/kernel/hibernate-asm.S  |  89 +++++++
 arch/riscv/kernel/hibernate.c      | 360 +++++++++++++++++++++++++++++
 7 files changed, 503 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 e2b656043abf..4555848a817f 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -690,6 +690,13 @@ menu "Power management options"
 
 source "kernel/power/Kconfig"
 
+config ARCH_HIBERNATION_POSSIBLE
+	def_bool y
+
+config ARCH_HIBERNATION_HEADER
+	def_bool y
+	depends on 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 ef1283d04b70..3de70d3e6ceb 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, .1
+	.endm
+
 #endif	/* __ASM_ASSEMBLER_H */
diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h
index 75419c5ca272..db40ae433aa9 100644
--- a/arch/riscv/include/asm/suspend.h
+++ b/arch/riscv/include/asm/suspend.h
@@ -21,6 +21,12 @@ struct suspend_context {
 #endif
 };
 
+/*
+ * This parameter will be assigned to 0 during resume and will be used by
+ * hibernation core for the subsequent resume sequence
+ */
+extern int in_suspend;
+
 /* Low-level CPU suspend entry function */
 int __cpu_suspend_enter(struct suspend_context *context);
 
@@ -36,4 +42,19 @@ int __cpu_resume_enter(unsigned long hartid, unsigned long context);
 /* Used to save and restore the csr */
 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);
+
+/* Used to restore the hibernated image */
+asmlinkage void restore_image(unsigned long resume_satp, unsigned long satp_temp,
+				unsigned long cpu_resume);
+asmlinkage int 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..a83d534b89bd
--- /dev/null
+++ b/arch/riscv/kernel/hibernate-asm.S
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Hibernation support specific for RISCV
+ *
+ * Copyright (C) 2023 StarFive Technology Co., Ltd.
+ *
+ * Author: Jee Heng Sia <jeeheng.sia@xxxxxxxxxxxxxxxx>
+ */
+
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/assembler.h>
+#include <asm/csr.h>
+
+#include <linux/linkage.h>
+
+/*
+ * This code is executed when resume from the hibernation.
+ *
+ * It begins with loading the temporary page table then restores the memory image.
+ * Finally branches to __hibernate_cpu_resume() to restore the state saved by
+ * swsusp_arch_suspend().
+ */
+
+/*
+ * int __hibernate_cpu_resume(void)
+ * Switch back to the hibernated image's page table prior to restore the CPU
+ * context.
+ *
+ * Always returns 0 to the C code.
+ */
+ENTRY(__hibernate_cpu_resume)
+	/* switch to hibernated image's page table */
+	csrw CSR_SATP, s0
+	sfence.vma
+
+	REG_L	a0, hibernate_cpu_context
+
+	/* Restore CSRs */
+	restore_csr
+
+	/* Restore registers (except A0 and T0-T6) */
+	restore_reg
+
+	/* Return zero value */
+	add	a0, zero, zero
+
+	/* Return to C code */
+	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(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(restore_image)
+
+/*
+ * The below code will be executed from a 'safe' page.
+ * It first switches to the temporary page table, then start to copy the pages
+ * back to the original memory location. Finally, it jumps to the __hibernate_cpu_resume()
+ * to restore the CPU context.
+ */
+ENTRY(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(core_restore_code)
diff --git a/arch/riscv/kernel/hibernate.c b/arch/riscv/kernel/hibernate.c
new file mode 100644
index 000000000000..bf7f3c781820
--- /dev/null
+++ b/arch/riscv/kernel/hibernate.c
@@ -0,0 +1,360 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Hibernation support specific for RISCV
+ *
+ * Copyright (C) 2023 StarFive Technology Co., Ltd.
+ *
+ * Author: Jee Heng Sia <jeeheng.sia@xxxxxxxxxxxxxxxx>
+ */
+
+#include <asm/barrier.h>
+#include <asm/cacheflush.h>
+#include <asm/mmu_context.h>
+#include <asm/page.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;
+
+/* CPU context to be saved */
+struct suspend_context *hibernate_cpu_context;
+
+unsigned long relocated_restore_code;
+
+/* Pointer to the temporary resume page table */
+pgd_t *resume_pg_dir;
+
+/**
+ * struct arch_hibernate_hdr_invariants - container to store kernel build version
+ * @uts_version: to save the build number and date so that the we are 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 executing 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 inline 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(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(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();
+
+		/* Invalidated Icache */
+		flush_icache_all();
+
+		/*
+		 * Tell the hibernation core that we've just restored
+		 * the memory
+		 */
+		in_suspend = 0;
+		sleep_cpu = -EINVAL;
+	}
+
+	return ret;
+}
+
+static unsigned long temp_pgtable_map_pte(pte_t *ptep, unsigned long vaddr, pgprot_t prot)
+{
+	uintptr_t pte_idx = pte_index(vaddr);
+
+	ptep[pte_idx] = pfn_pte(PFN_DOWN(__pa(vaddr)), prot);
+
+	return 0;
+}
+
+#ifndef __PAGETABLE_PMD_FOLDED
+#define temp_pgtable_map_pgd_next(pgdp, vaddr, prot)			\
+		(pgtable_l5_enabled ?					\
+		temp_pgtable_map_p4d(pgdp, vaddr, prot) :		\
+		(pgtable_l4_enabled ?					\
+		temp_pgtable_map_pud((pud_t *)pgdp, vaddr, prot) :	\
+		temp_pgtable_map_pmd((pmd_t *)pgdp, vaddr, prot)))
+
+static unsigned long temp_pgtable_map_pmd(pmd_t *pmdp, unsigned long vaddr, pgprot_t prot)
+{
+	uintptr_t pmd_idx = pmd_index(vaddr);
+	pte_t *ptep;
+
+	if (pmd_none(pmdp[pmd_idx])) {
+		ptep = (pte_t *)get_safe_page(GFP_ATOMIC);
+		if (!ptep)
+			return -ENOMEM;
+
+		memset(ptep, 0, PAGE_SIZE);
+		pmdp[pmd_idx] = pfn_pmd(PFN_DOWN(__pa(ptep)), PAGE_TABLE);
+	} else {
+		ptep = (pte_t *)__va(PFN_PHYS(_pmd_pfn(pmdp[pmd_idx])));
+	}
+
+	return temp_pgtable_map_pte(ptep, vaddr, prot);
+}
+
+static unsigned long temp_pgtable_map_pud(pud_t *pudp, unsigned long vaddr, pgprot_t prot)
+{
+	uintptr_t pud_index = pud_index(vaddr);
+	pmd_t *pmdp;
+
+	if (pud_val(pudp[pud_index]) == 0) {
+		pmdp = (pmd_t *)get_safe_page(GFP_ATOMIC);
+		if (!pmdp)
+			return -ENOMEM;
+
+		memset(pmdp, 0, PAGE_SIZE);
+		pudp[pud_index] = pfn_pud(PFN_DOWN(__pa(pmdp)), PAGE_TABLE);
+	} else {
+		pmdp = (pmd_t *)__va(PFN_PHYS(_pud_pfn(pudp[pud_index])));
+	}
+
+	return temp_pgtable_map_pmd(pmdp, vaddr, prot);
+}
+
+static unsigned long temp_pgtable_map_p4d(p4d_t *p4dp, unsigned long vaddr, pgprot_t prot)
+{
+	uintptr_t p4d_index = p4d_index(vaddr);
+	pud_t *pudp;
+
+	if (p4d_val(p4dp[p4d_index]) == 0) {
+		pudp = (pud_t *)get_safe_page(GFP_ATOMIC);
+		if (!pudp)
+			return -ENOMEM;
+
+		memset(pudp, 0, PAGE_SIZE);
+		p4dp[p4d_index] = pfn_p4d(PFN_DOWN(__pa(pudp)), PAGE_TABLE);
+	} else {
+		pudp = (pud_t *)__va(PFN_PHYS(_p4d_pfn(p4dp[p4d_index])));
+	}
+
+	return temp_pgtable_map_pud(pudp, vaddr, prot);
+}
+
+#else
+#define temp_pgtable_map_pgd_next(nextp, vaddr, prot)	\
+	temp_pgtable_map_pte((pte_t *)nextp, vaddr, prot)
+#endif /* __PAGETABLE_PMD_FOLDED */
+
+static unsigned long temp_pgtable_map_pgd(pgd_t *pgdp, unsigned long vaddr, pgprot_t prot)
+{
+	uintptr_t pgd_idx = pgd_index(vaddr);
+	void *nextp;
+
+	if (pgd_val(pgdp[pgd_idx]) == 0) {
+		nextp = (void *)get_safe_page(GFP_ATOMIC);
+		if (!nextp)
+			return -ENOMEM;
+
+		memset(nextp, 0, PAGE_SIZE);
+		pgdp[pgd_idx] = pfn_pgd(PFN_DOWN(__pa(nextp)), PAGE_TABLE);
+	} else {
+		nextp = (void *)__va(PFN_PHYS(_pgd_pfn(pgdp[pgd_idx])));
+	}
+
+	return temp_pgtable_map_pgd_next(nextp, vaddr, prot);
+}
+
+static unsigned long temp_pgtable_mapping(pgd_t *pgdp, unsigned long vaddr, pgprot_t prot)
+{
+	return temp_pgtable_map_pgd(pgdp, vaddr, prot);
+}
+
+static unsigned long relocate_restore_code(void)
+{
+	unsigned long ret;
+	void *page = (void *)get_safe_page(GFP_ATOMIC);
+
+	if (!page)
+		return -ENOMEM;
+
+	copy_page(page, core_restore_code);
+
+	/* Make the page containing the relocated code executable */
+	set_memory_x((unsigned long)page, 1);
+
+	ret = temp_pgtable_mapping(resume_pg_dir, (unsigned long)page, PAGE_KERNEL_READ_EXEC);
+	if (ret)
+		return ret;
+
+	return (unsigned long)page;
+}
+
+int swsusp_arch_resume(void)
+{
+	unsigned long addr = PAGE_OFFSET;
+	unsigned long 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;
+
+	/*
+	 * The pages need to be writable when restoring the image.
+	 * Create a second copy of page table just for the linear map, and use this when
+	 * restoring.
+	 */
+	for (; addr <= (unsigned long)pfn_to_virt(max_low_pfn); addr += PAGE_SIZE) {
+		ret = temp_pgtable_mapping(resume_pg_dir, addr, PAGE_KERNEL);
+		if (ret)
+			return (int)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 jump 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.
+	 */
+	ret = temp_pgtable_mapping(resume_pg_dir, (unsigned long)resume_hdr.restore_cpu_addr,
+					PAGE_KERNEL_READ_EXEC);
+	if (ret)
+		return ret;
+
+	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 = kcalloc(1, sizeof(struct suspend_context), GFP_KERNEL);
+
+	if (WARN_ON(!hibernate_cpu_context))
+		return -ENOMEM;
+
+	return 0;
+}
+
+early_initcall(riscv_hibernate_init);
-- 
2.34.1