Re: [PATCH v5 4/4] RISC-V: Add arch functions to support hibernation/suspend-to-disk
From: Alexandre Ghiti
Date: Wed Mar 08 2023 - 04:28:12 EST
On 3/8/23 10:08, Alexandre Ghiti wrote:
On 3/8/23 09:06, 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@xxxxxxxxxxxxxxxx>
Reviewed-by: Ley Foon Tan <leyfoon.tan@xxxxxxxxxxxxxxxx>
Reviewed-by: Mason Huo <mason.huo@xxxxxxxxxxxxxxxx>
---
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 | 424 +++++++++++++++++++++++++++++
7 files changed, 552 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@xxxxxxxxxxxxxxxx>
+ */
+
+#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..8fab50122e54
--- /dev/null
+++ b/arch/riscv/kernel/hibernate.c
@@ -0,0 +1,424 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Hibernation support 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/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));
Hmm weird protections, PAGE_PRESENT and PAGE_READ are not even set.
Shouldn't you use PAGE_KERNEL_EXEC instead?
Forget this one, that's the protections you add, so that's good :)
+ 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.
+ *
+ */
+ start = (unsigned long)resume_hdr.restore_cpu_addr;
+ end = start + PAGE_SIZE;
+
+ ret = temp_pgtable_mapping(resume_pg_dir, start, end,
__pgprot(_PAGE_WRITE | _PAGE_EXEC));
+ if (ret)
+ return ret;
You set the linear mapping as executable so no need for this.
+
+ 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);
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