Date:   Wed, 8 Mar 2023 10:27:58 +0100
From:   Alexandre Ghiti <alex@...ti.fr>
To:     Sia Jee Heng <jeeheng.sia@...rfivetech.com>,
        paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        leyfoon.tan@...rfivetech.com, mason.huo@...rfivetech.com
Subject: Re: [PATCH v5 4/4] RISC-V: Add arch functions to support
 hibernation/suspend-to-disk


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@...rfivetech.com>
>> Reviewed-by: Ley Foon Tan <leyfoon.tan@...rfivetech.com>
>> Reviewed-by: Mason Huo <mason.huo@...rfivetech.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      | 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@...rfivetech.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..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@...rfivetech.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));
>
>
> 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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