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[209.132.180.67]) by mx.google.com with ESMTP id u11si2073228eda.235.2019.10.22.06.20.48; Tue, 22 Oct 2019 06:21:14 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388039AbfJVLSn (ORCPT + 99 others); Tue, 22 Oct 2019 07:18:43 -0400 Received: from [217.140.110.172] ([217.140.110.172]:49616 "EHLO foss.arm.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S2387903AbfJVLSn (ORCPT ); Tue, 22 Oct 2019 07:18:43 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D56B51000; Tue, 22 Oct 2019 04:18:21 -0700 (PDT) Received: from [10.162.40.145] (p8cg001049571a15.blr.arm.com [10.162.40.145]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5A0F93F718; Tue, 22 Oct 2019 04:18:09 -0700 (PDT) Subject: Re: [PATCH V7] mm/debug: Add tests validating architecture page table helpers To: Christophe Leroy , linux-mm@kvack.org Cc: Andrew Morton , Vlastimil Babka , Greg Kroah-Hartman , Thomas Gleixner , Mike Rapoport , Jason Gunthorpe , Dan Williams , Peter Zijlstra , Michal Hocko , Mark Rutland , Mark Brown , Steven Price , Ard Biesheuvel , Masahiro Yamada , Kees Cook , Tetsuo Handa , Matthew Wilcox , Sri Krishna chowdary , Dave Hansen , Russell King - ARM Linux , Michael Ellerman , Paul Mackerras , Martin Schwidefsky , Heiko Carstens , "David S. Miller" , Vineet Gupta , James Hogan , Paul Burton , Ralf Baechle , "Kirill A . Shutemov" , Gerald Schaefer , Ingo Molnar , linux-snps-arc@lists.infradead.org, linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org References: <1571625739-29943-1-git-send-email-anshuman.khandual@arm.com> <1571625739-29943-2-git-send-email-anshuman.khandual@arm.com> <535564eb-65ea-69ab-977d-0038a9e4f785@c-s.fr> From: Anshuman Khandual Message-ID: Date: Tue, 22 Oct 2019 16:48:38 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <535564eb-65ea-69ab-977d-0038a9e4f785@c-s.fr> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/22/2019 12:41 PM, Christophe Leroy wrote: > > > On 10/21/2019 02:42 AM, Anshuman Khandual wrote: >> This adds tests which will validate architecture page table helpers and >> other accessors in their compliance with expected generic MM semantics. >> This will help various architectures in validating changes to existing >> page table helpers or addition of new ones. >> >> This test covers basic page table entry transformations including but not >> limited to old, young, dirty, clean, write, write protect etc at various >> level along with populating intermediate entries with next page table page >> and validating them. >> >> Test page table pages are allocated from system memory with required size >> and alignments. The mapped pfns at page table levels are derived from a >> real pfn representing a valid kernel text symbol. This test gets called >> right after page_alloc_init_late(). >> >> This gets build and run when CONFIG_DEBUG_VM_PGTABLE is selected along with >> CONFIG_VM_DEBUG. Architectures willing to subscribe this test also need to >> select CONFIG_ARCH_HAS_DEBUG_VM_PGTABLE which for now is limited to x86 and >> arm64. Going forward, other architectures too can enable this after fixing >> build or runtime problems (if any) with their page table helpers. >> >> Folks interested in making sure that a given platform's page table helpers >> conform to expected generic MM semantics should enable the above config >> which will just trigger this test during boot. Any non conformity here will >> be reported as an warning which would need to be fixed. This test will help >> catch any changes to the agreed upon semantics expected from generic MM and >> enable platforms to accommodate it thereafter. >> >> Cc: Andrew Morton >> Cc: Vlastimil Babka >> Cc: Greg Kroah-Hartman >> Cc: Thomas Gleixner >> Cc: Mike Rapoport >> Cc: Jason Gunthorpe >> Cc: Dan Williams >> Cc: Peter Zijlstra >> Cc: Michal Hocko >> Cc: Mark Rutland >> Cc: Mark Brown >> Cc: Steven Price >> Cc: Ard Biesheuvel >> Cc: Masahiro Yamada >> Cc: Kees Cook >> Cc: Tetsuo Handa >> Cc: Matthew Wilcox >> Cc: Sri Krishna chowdary >> Cc: Dave Hansen >> Cc: Russell King - ARM Linux >> Cc: Michael Ellerman >> Cc: Paul Mackerras >> Cc: Martin Schwidefsky >> Cc: Heiko Carstens >> Cc: "David S. Miller" >> Cc: Vineet Gupta >> Cc: James Hogan >> Cc: Paul Burton >> Cc: Ralf Baechle >> Cc: Kirill A. Shutemov >> Cc: Gerald Schaefer >> Cc: Christophe Leroy >> Cc: Ingo Molnar >> Cc: linux-snps-arc@lists.infradead.org >> Cc: linux-mips@vger.kernel.org >> Cc: linux-arm-kernel@lists.infradead.org >> Cc: linux-ia64@vger.kernel.org >> Cc: linuxppc-dev@lists.ozlabs.org >> Cc: linux-s390@vger.kernel.org >> Cc: linux-sh@vger.kernel.org >> Cc: sparclinux@vger.kernel.org >> Cc: x86@kernel.org >> Cc: linux-kernel@vger.kernel.org >> >> Tested-by: Christophe Leroy         #PPC32 >> Suggested-by: Catalin Marinas >> Signed-off-by: Andrew Morton >> Signed-off-by: Christophe Leroy >> Signed-off-by: Anshuman Khandual >> --- > > The cover letter have the exact same title as this patch. I think a cover letter is not necessary for a singleton series. Right, but it became singleton series in this version :) > > The history (and any other information you don't want to include in the commit message) can be added here, below the '---'. That way it is in the mail but won't be included in the commit. I was aware about that but the change log here was big, hence just choose to have that separately in a cover letter. As you said, I guess the cover letter is probably not required anymore. Will add it here in the patch, next time around. > >>   .../debug/debug-vm-pgtable/arch-support.txt        |  34 ++ >>   arch/arm64/Kconfig                                 |   1 + >>   arch/x86/Kconfig                                   |   1 + >>   arch/x86/include/asm/pgtable_64.h                  |   6 + >>   include/asm-generic/pgtable.h                      |   6 + >>   init/main.c                                        |   1 + >>   lib/Kconfig.debug                                  |  21 ++ >>   mm/Makefile                                        |   1 + >>   mm/debug_vm_pgtable.c                              | 388 +++++++++++++++++++++ >>   9 files changed, 459 insertions(+) >>   create mode 100644 Documentation/features/debug/debug-vm-pgtable/arch-support.txt >>   create mode 100644 mm/debug_vm_pgtable.c >> >> diff --git a/Documentation/features/debug/debug-vm-pgtable/arch-support.txt b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt >> new file mode 100644 >> index 0000000..d6b8185 >> --- /dev/null >> +++ b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt >> @@ -0,0 +1,34 @@ >> +# >> +# Feature name:          debug-vm-pgtable >> +#         Kconfig:       ARCH_HAS_DEBUG_VM_PGTABLE >> +#         description:   arch supports pgtable tests for semantics compliance >> +# >> +    ----------------------- >> +    |         arch |status| >> +    ----------------------- >> +    |       alpha: | TODO | >> +    |         arc: | TODO | >> +    |         arm: | TODO | >> +    |       arm64: |  ok  | >> +    |         c6x: | TODO | >> +    |        csky: | TODO | >> +    |       h8300: | TODO | >> +    |     hexagon: | TODO | >> +    |        ia64: | TODO | >> +    |        m68k: | TODO | >> +    |  microblaze: | TODO | >> +    |        mips: | TODO | >> +    |       nds32: | TODO | >> +    |       nios2: | TODO | >> +    |    openrisc: | TODO | >> +    |      parisc: | TODO | >> +    |     powerpc: | TODO | > > Say ok on ppc32 Will do. > >> +    |       riscv: | TODO | >> +    |        s390: | TODO | >> +    |          sh: | TODO | >> +    |       sparc: | TODO | >> +    |          um: | TODO | >> +    |   unicore32: | TODO | >> +    |         x86: |  ok  | >> +    |      xtensa: | TODO | >> +    ----------------------- >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index 1b6ea5a..ea62c87 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -11,6 +11,7 @@ config ARM64 >>       select ACPI_PPTT if ACPI >>       select ARCH_CLOCKSOURCE_DATA >>       select ARCH_HAS_DEBUG_VIRTUAL >> +    select ARCH_HAS_DEBUG_VM_PGTABLE >>       select ARCH_HAS_DEVMEM_IS_ALLOWED >>       select ARCH_HAS_DMA_COHERENT_TO_PFN >>       select ARCH_HAS_DMA_PREP_COHERENT >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index abe822d..13c9bd9 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -61,6 +61,7 @@ config X86 >>       select ARCH_CLOCKSOURCE_INIT >>       select ARCH_HAS_ACPI_TABLE_UPGRADE    if ACPI >>       select ARCH_HAS_DEBUG_VIRTUAL >> +    select ARCH_HAS_DEBUG_VM_PGTABLE >>       select ARCH_HAS_DEVMEM_IS_ALLOWED >>       select ARCH_HAS_ELF_RANDOMIZE >>       select ARCH_HAS_FAST_MULTIPLIER > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 3e56c9c2f16e..c50d7cfa566b 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -120,6 +120,7 @@ config PPC >      # >      select ARCH_32BIT_OFF_T if PPC32 >      select ARCH_HAS_DEBUG_VIRTUAL > +    select ARCH_HAS_DEBUG_VM_PGTABLE if PPC32 >      select ARCH_HAS_DEVMEM_IS_ALLOWED >      select ARCH_HAS_ELF_RANDOMIZE >      select ARCH_HAS_FORTIFY_SOURCE > > Will add this. >> diff --git a/arch/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h >> index 0b6c4042..fb0e76d 100644 >> --- a/arch/x86/include/asm/pgtable_64.h >> +++ b/arch/x86/include/asm/pgtable_64.h >> @@ -53,6 +53,12 @@ static inline void sync_initial_page_table(void) { } >>     struct mm_struct; >>   +#define mm_p4d_folded mm_p4d_folded >> +static inline bool mm_p4d_folded(struct mm_struct *mm) >> +{ >> +    return !pgtable_l5_enabled(); >> +} >> + >>   void set_pte_vaddr_p4d(p4d_t *p4d_page, unsigned long vaddr, pte_t new_pte); >>   void set_pte_vaddr_pud(pud_t *pud_page, unsigned long vaddr, pte_t new_pte); >>   diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h >> index 9cdcbc7..9eb02e1 100644 >> --- a/include/asm-generic/pgtable.h >> +++ b/include/asm-generic/pgtable.h >> @@ -1168,6 +1168,12 @@ static inline bool arch_has_pfn_modify_check(void) >>   # define PAGE_KERNEL_EXEC PAGE_KERNEL >>   #endif >>   +#ifdef CONFIG_DEBUG_VM_PGTABLE >> +extern void debug_vm_pgtable(void); >> +#else >> +static inline void debug_vm_pgtable(void) { } >> +#endif >> + >>   #endif /* !__ASSEMBLY__ */ >>     #ifndef io_remap_pfn_range >> diff --git a/init/main.c b/init/main.c >> index 91f6ebb..af8379e 100644 >> --- a/init/main.c >> +++ b/init/main.c >> @@ -1185,6 +1185,7 @@ static noinline void __init kernel_init_freeable(void) >>       sched_init_smp(); >>         page_alloc_init_late(); >> +    debug_vm_pgtable(); >>       /* Initialize page ext after all struct pages are initialized. */ >>       page_ext_init(); >>   diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug >> index 9c60d7d..cf48d95 100644 >> --- a/lib/Kconfig.debug >> +++ b/lib/Kconfig.debug >> @@ -690,6 +690,27 @@ config DEBUG_VM_PGFLAGS >>           If unsure, say N. >>   +config ARCH_HAS_DEBUG_VM_PGTABLE >> +    bool >> +    help >> +      An architecture should select this when it can successfully >> +      build and run DEBUG_VM_PGTABLE. >> + >> +config DEBUG_VM_PGTABLE >> +    bool "Debug arch page table for semantics compliance" >> +    depends on MMU >> +    depends on DEBUG_VM >> +    depends on ARCH_HAS_DEBUG_VM_PGTABLE >> +    help >> +      This option provides a debug method which can be used to test >> +      architecture page table helper functions on various platforms in >> +      verifying if they comply with expected generic MM semantics. This >> +      will help architecture code in making sure that any changes or >> +      new additions of these helpers still conform to expected >> +      semantics of the generic MM. >> + >> +      If unsure, say N. >> + > > Would be nice to have that one also indented like the other DEBUG_VM_XXXXX (see below). > > Stack utilization instrumentation (DEBUG_STACK_USAGE) [N/y/?] n > Debug VM (DEBUG_VM) [N/y/?] (NEW) y >   Debug VMA caching (DEBUG_VM_VMACACHE) [N/y/?] (NEW) >   Debug VM red-black trees (DEBUG_VM_RB) [N/y/?] (NEW) >   Debug page-flags operations (DEBUG_VM_PGFLAGS) [N/y/?] (NEW) > Debug arch page table for semantics compliance (DEBUG_VM_PGTABLE) [N/y/?] (NEW) > Debug VM translations (DEBUG_VIRTUAL) [N/y/?] n > > > For that, just move config ARCH_HAS_DEBUG_VM_PGTABLE somewhere else, maybe before DEBUG_VM or just after DEBUG_VM_PGTABLE Initially I had ARCH_HAS_DEBUG_VM_PGTABLE after DEBUG_VM_PGTABLE but reversed that because of it's dependency. So will probably move it before DEBUG_VM. > > >>   config ARCH_HAS_DEBUG_VIRTUAL >>       bool >>   diff --git a/mm/Makefile b/mm/Makefile >> index d996846..2f085b9 100644 >> --- a/mm/Makefile >> +++ b/mm/Makefile >> @@ -86,6 +86,7 @@ obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o >>   obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o >>   obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o >>   obj-$(CONFIG_DEBUG_RODATA_TEST) += rodata_test.o >> +obj-$(CONFIG_DEBUG_VM_PGTABLE) += debug_vm_pgtable.o >>   obj-$(CONFIG_PAGE_OWNER) += page_owner.o >>   obj-$(CONFIG_CLEANCACHE) += cleancache.o >>   obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o >> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c >> new file mode 100644 >> index 0000000..9472566 >> --- /dev/null >> +++ b/mm/debug_vm_pgtable.c >> @@ -0,0 +1,388 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * This kernel test validates architecture page table helpers and >> + * accessors and helps in verifying their continued compliance with >> + * expected generic MM semantics. >> + * >> + * Copyright (C) 2019 ARM Ltd. >> + * >> + * Author: Anshuman Khandual >> + */ >> +#define pr_fmt(fmt) "arch_pgtable_test: %s " fmt, __func__ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +/* >> + * Basic operations >> + * >> + * mkold(entry)            = An old and not a young entry >> + * mkyoung(entry)        = A young and not an old entry >> + * mkdirty(entry)        = A dirty and not a clean entry >> + * mkclean(entry)        = A clean and not a dirty entry >> + * mkwrite(entry)        = A write and not a write protected entry >> + * wrprotect(entry)        = A write protected and not a write entry >> + * pxx_bad(entry)        = A mapped and non-table entry >> + * pxx_same(entry1, entry2)    = Both entries hold the exact same value >> + */ >> +#define VMFLAGS    (VM_READ|VM_WRITE|VM_EXEC) >> + >> +/* >> + * On s390 platform, the lower 12 bits are used to identify given page table >> + * entry type and for other arch specific requirements. But these bits might >> + * affect the ability to clear entries with pxx_clear(). So while loading up >> + * the entries skip all lower 12 bits in order to accommodate s390 platform. >> + * It does not have affect any other platform. >> + */ >> +#define RANDOM_ORVALUE    (0xfffffffffffff000UL) >> +#define RANDOM_NZVALUE    (0xff) >> + >> +static void __init pte_basic_tests(unsigned long pfn, pgprot_t prot) >> +{ >> +    pte_t pte = pfn_pte(pfn, prot); >> + >> +    WARN_ON(!pte_same(pte, pte)); >> +    WARN_ON(!pte_young(pte_mkyoung(pte))); >> +    WARN_ON(!pte_dirty(pte_mkdirty(pte))); >> +    WARN_ON(!pte_write(pte_mkwrite(pte))); >> +    WARN_ON(pte_young(pte_mkold(pte))); >> +    WARN_ON(pte_dirty(pte_mkclean(pte))); >> +    WARN_ON(pte_write(pte_wrprotect(pte))); >> +} >> + >> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE >> +static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) >> +{ >> +    pmd_t pmd = pfn_pmd(pfn, prot); >> + >> +    WARN_ON(!pmd_same(pmd, pmd)); >> +    WARN_ON(!pmd_young(pmd_mkyoung(pmd))); >> +    WARN_ON(!pmd_dirty(pmd_mkdirty(pmd))); >> +    WARN_ON(!pmd_write(pmd_mkwrite(pmd))); >> +    WARN_ON(pmd_young(pmd_mkold(pmd))); >> +    WARN_ON(pmd_dirty(pmd_mkclean(pmd))); >> +    WARN_ON(pmd_write(pmd_wrprotect(pmd))); >> +    /* >> +     * A huge page does not point to next level page table >> +     * entry. Hence this must qualify as pmd_bad(). >> +     */ >> +    WARN_ON(!pmd_bad(pmd_mkhuge(pmd))); >> +} >> +#else >> +static void __init pmd_basic_tests(unsigned long pfn, pgprot_t prot) { } >> +#endif >> + >> +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD >> +static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) >> +{ >> +    pud_t pud = pfn_pud(pfn, prot); >> + >> +    WARN_ON(!pud_same(pud, pud)); >> +    WARN_ON(!pud_young(pud_mkyoung(pud))); >> +    WARN_ON(!pud_write(pud_mkwrite(pud))); >> +    WARN_ON(pud_write(pud_wrprotect(pud))); >> +    WARN_ON(pud_young(pud_mkold(pud))); >> + >> +    if (mm_pmd_folded(mm) || __is_defined(ARCH_HAS_4LEVEL_HACK)) >> +        return; >> + >> +    /* >> +     * A huge page does not point to next level page table >> +     * entry. Hence this must qualify as pud_bad(). >> +     */ >> +    WARN_ON(!pud_bad(pud_mkhuge(pud))); >> +} >> +#else >> +static void __init pud_basic_tests(unsigned long pfn, pgprot_t prot) { } >> +#endif >> + >> +static void __init p4d_basic_tests(unsigned long pfn, pgprot_t prot) >> +{ >> +    p4d_t p4d; >> + >> +    memset(&p4d, RANDOM_NZVALUE, sizeof(p4d_t)); >> +    WARN_ON(!p4d_same(p4d, p4d)); >> +} >> + >> +static void __init pgd_basic_tests(unsigned long pfn, pgprot_t prot) >> +{ >> +    pgd_t pgd; >> + >> +    memset(&pgd, RANDOM_NZVALUE, sizeof(pgd_t)); >> +    WARN_ON(!pgd_same(pgd, pgd)); >> +} >> + >> +#ifndef __ARCH_HAS_4LEVEL_HACK >> +static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp) >> +{ >> +    pud_t pud = READ_ONCE(*pudp); >> + >> +    if (mm_pmd_folded(mm)) >> +        return; >> + >> +    pud = __pud(pud_val(pud) | RANDOM_ORVALUE); >> +    WRITE_ONCE(*pudp, pud); >> +    pud_clear(pudp); >> +    pud = READ_ONCE(*pudp); >> +    WARN_ON(!pud_none(pud)); >> +} >> + >> +static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp, >> +                      pmd_t *pmdp) >> +{ >> +    pud_t pud; >> + >> +    if (mm_pmd_folded(mm)) >> +        return; >> +    /* >> +     * This entry points to next level page table page. >> +     * Hence this must not qualify as pud_bad(). >> +     */ >> +    pmd_clear(pmdp); >> +    pud_clear(pudp); >> +    pud_populate(mm, pudp, pmdp); >> +    pud = READ_ONCE(*pudp); >> +    WARN_ON(pud_bad(pud)); >> +} >> +#else >> +static void __init pud_clear_tests(struct mm_struct *mm, pud_t *pudp) { } >> +static void __init pud_populate_tests(struct mm_struct *mm, pud_t *pudp, >> +                      pmd_t *pmdp) >> +{ >> +} >> +#endif >> + >> +#ifndef __ARCH_HAS_5LEVEL_HACK >> +static void __init p4d_clear_tests(struct mm_struct *mm, p4d_t *p4dp) >> +{ >> +    p4d_t p4d = READ_ONCE(*p4dp); >> + >> +    if (mm_pud_folded(mm)) >> +        return; >> + >> +    p4d = __p4d(p4d_val(p4d) | RANDOM_ORVALUE); >> +    WRITE_ONCE(*p4dp, p4d); >> +    p4d_clear(p4dp); >> +    p4d = READ_ONCE(*p4dp); >> +    WARN_ON(!p4d_none(p4d)); >> +} >> + >> +static void __init p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp, >> +                      pud_t *pudp) >> +{ >> +    p4d_t p4d; >> + >> +    if (mm_pud_folded(mm)) >> +        return; >> + >> +    /* >> +     * This entry points to next level page table page. >> +     * Hence this must not qualify as p4d_bad(). >> +     */ >> +    pud_clear(pudp); >> +    p4d_clear(p4dp); >> +    p4d_populate(mm, p4dp, pudp); >> +    p4d = READ_ONCE(*p4dp); >> +    WARN_ON(p4d_bad(p4d)); >> +} >> + >> +static void __init pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp) >> +{ >> +    pgd_t pgd = READ_ONCE(*pgdp); >> + >> +    if (mm_p4d_folded(mm)) >> +        return; >> + >> +    pgd = __pgd(pgd_val(pgd) | RANDOM_ORVALUE); >> +    WRITE_ONCE(*pgdp, pgd); >> +    pgd_clear(pgdp); >> +    pgd = READ_ONCE(*pgdp); >> +    WARN_ON(!pgd_none(pgd)); >> +} >> + >> +static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp, >> +                      p4d_t *p4dp) >> +{ >> +    pgd_t pgd; >> + >> +    if (mm_p4d_folded(mm)) >> +        return; >> + >> +    /* >> +     * This entry points to next level page table page. >> +     * Hence this must not qualify as pgd_bad(). >> +     */ >> +    p4d_clear(p4dp); >> +    pgd_clear(pgdp); >> +    pgd_populate(mm, pgdp, p4dp); >> +    pgd = READ_ONCE(*pgdp); >> +    WARN_ON(pgd_bad(pgd)); >> +} >> +#else >> +static void __init p4d_clear_tests(struct mm_struct *mm, p4d_t *p4dp) { } >> +static void __init pgd_clear_tests(struct mm_struct *mm, pgd_t *pgdp) { } >> +static void __init p4d_populate_tests(struct mm_struct *mm, p4d_t *p4dp, >> +                      pud_t *pudp) >> +{ >> +} >> +static void __init pgd_populate_tests(struct mm_struct *mm, pgd_t *pgdp, >> +                      p4d_t *p4dp) >> +{ >> +} >> +#endif >> + >> +static void __init pte_clear_tests(struct mm_struct *mm, pte_t *ptep) >> +{ >> +    pte_t pte = READ_ONCE(*ptep); >> + >> +    pte = __pte(pte_val(pte) | RANDOM_ORVALUE); >> +    WRITE_ONCE(*ptep, pte); >> +    pte_clear(mm, 0, ptep); >> +    pte = READ_ONCE(*ptep); >> +    WARN_ON(!pte_none(pte)); >> +} >> + >> +static void __init pmd_clear_tests(struct mm_struct *mm, pmd_t *pmdp) >> +{ >> +    pmd_t pmd = READ_ONCE(*pmdp); >> + >> +    pmd = __pmd(pmd_val(pmd) | RANDOM_ORVALUE); >> +    WRITE_ONCE(*pmdp, pmd); >> +    pmd_clear(pmdp); >> +    pmd = READ_ONCE(*pmdp); >> +    WARN_ON(!pmd_none(pmd)); >> +} >> + >> +static void __init pmd_populate_tests(struct mm_struct *mm, pmd_t *pmdp, >> +                      pgtable_t pgtable) >> +{ >> +    pmd_t pmd; >> + >> +    /* >> +     * This entry points to next level page table page. >> +     * Hence this must not qualify as pmd_bad(). >> +     */ >> +    pmd_clear(pmdp); >> +    pmd_populate(mm, pmdp, pgtable); >> +    pmd = READ_ONCE(*pmdp); >> +    WARN_ON(pmd_bad(pmd)); >> +} >> + >> +static unsigned long __init get_random_vaddr(void) >> +{ >> +    unsigned long random_vaddr, random_pages, total_user_pages; >> + >> +    total_user_pages = (TASK_SIZE - FIRST_USER_ADDRESS) / PAGE_SIZE; >> + >> +    random_pages = get_random_long() % total_user_pages; >> +    random_vaddr = FIRST_USER_ADDRESS + random_pages * PAGE_SIZE; >> + >> +    WARN_ON((random_vaddr > TASK_SIZE) || >> +        (random_vaddr < FIRST_USER_ADDRESS)); >> +    return random_vaddr; >> +} >> + >> +void __init debug_vm_pgtable(void) >> +{ >> +    struct mm_struct *mm; >> +    pgd_t *pgdp; >> +    p4d_t *p4dp, *saved_p4dp; >> +    pud_t *pudp, *saved_pudp; >> +    pmd_t *pmdp, *saved_pmdp, pmd; >> +    pte_t *ptep; >> +    pgtable_t saved_ptep; >> +    pgprot_t prot; >> +    phys_addr_t paddr; >> +    unsigned long vaddr, pte_aligned, pmd_aligned; >> +    unsigned long pud_aligned, p4d_aligned, pgd_aligned; > > I think an information message would be nice: > > diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c > index 9472566b7e53..ed7cc3dfc968 100644 > --- a/mm/debug_vm_pgtable.c > +++ b/mm/debug_vm_pgtable.c > @@ -313,6 +313,8 @@ void __init debug_vm_pgtable(void) >      unsigned long vaddr, pte_aligned, pmd_aligned; >      unsigned long pud_aligned, p4d_aligned, pgd_aligned; > > +    pr_info("Validating architecture page table helpers\n"); > + >      prot = vm_get_page_prot(VMFLAGS); >      vaddr = get_random_vaddr(); >      mm = mm_alloc(); Sure, will add. Thanks ! > > Christophe > >> + >> +    prot = vm_get_page_prot(VMFLAGS); >> +    vaddr = get_random_vaddr(); >> +    mm = mm_alloc(); >> +    if (!mm) { >> +        pr_err("mm_struct allocation failed\n"); >> +        return; >> +    } >> + >> +    /* >> +     * PFN for mapping at PTE level is determined from a standard kernel >> +     * text symbol. But pfns for higher page table levels are derived by >> +     * masking lower bits of this real pfn. These derived pfns might not >> +     * exist on the platform but that does not really matter as pfn_pxx() >> +     * helpers will still create appropriate entries for the test. This >> +     * helps avoid large memory block allocations to be used for mapping >> +     * at higher page table levels. >> +     */ >> +    WARN_ON(!virt_addr_valid(&start_kernel)); >> +    paddr = __pa(&start_kernel); >> + >> +    pte_aligned = (paddr & PAGE_MASK) >> PAGE_SHIFT; >> +    pmd_aligned = (paddr & PMD_MASK) >> PAGE_SHIFT; >> +    pud_aligned = (paddr & PUD_MASK) >> PAGE_SHIFT; >> +    p4d_aligned = (paddr & P4D_MASK) >> PAGE_SHIFT; >> +    pgd_aligned = (paddr & PGDIR_MASK) >> PAGE_SHIFT; >> + >> +    pgdp = pgd_offset(mm, vaddr); >> +    p4dp = p4d_alloc(mm, pgdp, vaddr); >> +    pudp = pud_alloc(mm, p4dp, vaddr); >> +    pmdp = pmd_alloc(mm, pudp, vaddr); >> +    ptep = pte_alloc_map(mm, pmdp, vaddr); >> + >> +    /* >> +     * Save all the page table page addresses as the page table >> +     * entries will be used for testing with random or garbage >> +     * values. These saved addresses will be used for freeing >> +     * page table pages. >> +     */ >> +    pmd = READ_ONCE(*pmdp); >> +    saved_p4dp = p4d_offset(pgdp, 0UL); >> +    saved_pudp = pud_offset(p4dp, 0UL); >> +    saved_pmdp = pmd_offset(pudp, 0UL); >> +    saved_ptep = pmd_pgtable(pmd); >> + >> +    pte_basic_tests(pte_aligned, prot); >> +    pmd_basic_tests(pmd_aligned, prot); >> +    pud_basic_tests(pud_aligned, prot); >> +    p4d_basic_tests(p4d_aligned, prot); >> +    pgd_basic_tests(pgd_aligned, prot); >> + >> +    pte_clear_tests(mm, ptep); >> +    pmd_clear_tests(mm, pmdp); >> +    pud_clear_tests(mm, pudp); >> +    p4d_clear_tests(mm, p4dp); >> +    pgd_clear_tests(mm, pgdp); >> + >> +    pte_unmap(ptep); >> + >> +    pmd_populate_tests(mm, pmdp, saved_ptep); >> +    pud_populate_tests(mm, pudp, saved_pmdp); >> +    p4d_populate_tests(mm, p4dp, saved_pudp); >> +    pgd_populate_tests(mm, pgdp, saved_p4dp); >> + >> +    p4d_free(mm, saved_p4dp); >> +    pud_free(mm, saved_pudp); >> +    pmd_free(mm, saved_pmdp); >> +    pte_free(mm, saved_ptep); >> + >> +    mm_dec_nr_puds(mm); >> +    mm_dec_nr_pmds(mm); >> +    mm_dec_nr_ptes(mm); >> +    __mmdrop(mm); >> +} >> >