[PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[Anshuman Khandual]

This series adds a test validation for architecture exported page table
helpers. Patch in the series adds basic transformation tests at various
levels of the page table. Before that it exports gigantic page allocation
function from HugeTLB.

This test was originally suggested by Catalin during arm64 THP migration
RFC discussion earlier. Going forward it can include more specific tests
with respect to various generic MM functions like THP, HugeTLB etc and
platform specific tests.

https://lore.kernel.org/linux-mm/20190628102003.GA56463@arrakis.emea.arm.com/

Changes in V6:

- Moved alloc_gigantic_page_order() into mm/page_alloc.c per Michal
- Moved alloc_gigantic_page_order() within CONFIG_CONTIG_ALLOC in the test
- Folded Andrew's include/asm-generic/pgtable.h fix into the test patch 2/2

Changes in V5: (https://patchwork.kernel.org/project/linux-mm/list/?series=185991)

- Redefined and moved X86 mm_p4d_folded() into a different header per Kirill/Ingo
- Updated the config option comment per Ingo and dropped 'kernel module' reference
- Updated the commit message and dropped 'kernel module' reference
- Changed DEBUG_ARCH_PGTABLE_TEST into DEBUG_VM_PGTABLE per Ingo
- Moved config option from mm/Kconfig.debug into lib/Kconfig.debug
- Renamed core test function arch_pgtable_tests() as debug_vm_pgtable()
- Renamed mm/arch_pgtable_test.c as mm/debug_vm_pgtable.c
- debug_vm_pgtable() gets called from kernel_init_freeable() after init_mm_internals()
- Added an entry in Documentation/features/debug/ per Ingo
- Enabled the test on arm64 and x86 platforms for now

Changes in V4: (https://patchwork.kernel.org/project/linux-mm/list/?series=183465)

- Disable DEBUG_ARCH_PGTABLE_TEST for ARM and IA64 platforms

Changes in V3: (https://lore.kernel.org/patchwork/project/lkml/list/?series=411216)

- Changed test trigger from module format into late_initcall()
- Marked all functions with __init to be freed after completion
- Changed all __PGTABLE_PXX_FOLDED checks as mm_pxx_folded()
- Folded in PPC32 fixes from Christophe

Changes in V2:

https://lore.kernel.org/linux-mm/1568268173-31302-1-git-send-email-anshuman.khandual@arm.com/T/#t

- Fixed small typo error in MODULE_DESCRIPTION()
- Fixed m64k build problems for lvalue concerns in pmd_xxx_tests()
- Fixed dynamic page table level folding problems on x86 as per Kirril
- Fixed second pointers during pxx_populate_tests() per Kirill and Gerald
- Allocate and free pte table with pte_alloc_one/pte_free per Kirill
- Modified pxx_clear_tests() to accommodate s390 lower 12 bits situation
- Changed RANDOM_NZVALUE value from 0xbe to 0xff
- Changed allocation, usage, free sequence for saved_ptep
- Renamed VMA_FLAGS as VMFLAGS
- Implemented a new method for random vaddr generation
- Implemented some other cleanups
- Dropped extern reference to mm_alloc()
- Created and exported new alloc_gigantic_page_order()
- Dropped the custom allocator and used new alloc_gigantic_page_order()

Changes in V1:

https://lore.kernel.org/linux-mm/1567497706-8649-1-git-send-email-anshuman.khandual@arm.com/

- Added fallback mechanism for PMD aligned memory allocation failure

Changes in RFC V2:

https://lore.kernel.org/linux-mm/1565335998-22553-1-git-send-email-anshuman.khandual@arm.com/T/#u

- Moved test module and it's config from lib/ to mm/
- Renamed config TEST_ARCH_PGTABLE as DEBUG_ARCH_PGTABLE_TEST
- Renamed file from test_arch_pgtable.c to arch_pgtable_test.c
- Added relevant MODULE_DESCRIPTION() and MODULE_AUTHOR() details
- Dropped loadable module config option
- Basic tests now use memory blocks with required size and alignment
- PUD aligned memory block gets allocated with alloc_contig_range()
- If PUD aligned memory could not be allocated it falls back on PMD aligned
  memory block from page allocator and pud_* tests are skipped
- Clear and populate tests now operate on real in memory page table entries
- Dummy mm_struct gets allocated with mm_alloc()
- Dummy page table entries get allocated with [pud|pmd|pte]_alloc_[map]()
- Simplified [p4d|pgd]_basic_tests(), now has random values in the entries

Original RFC V1:

https://lore.kernel.org/linux-mm/1564037723-26676-1-git-send-email-anshuman.khandual@arm.com/

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Steven Price <Steven.Price@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sri Krishna chowdary <schowdary@nvidia.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
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


Anshuman Khandual (2):
  mm/page_alloc: Make alloc_gigantic_page() available for general use
  mm/debug: Add tests validating architecture page table helpers

 .../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 +
 include/linux/gfp.h                           |   3 +
 init/main.c                                   |   1 +
 lib/Kconfig.debug                             |  21 +
 mm/Makefile                                   |   1 +
 mm/debug_vm_pgtable.c                         | 450 ++++++++++++++++++
 mm/hugetlb.c                                  |  76 +--
 mm/page_alloc.c                               |  98 ++++
 12 files changed, 623 insertions(+), 75 deletions(-)
 create mode 100644 Documentation/features/debug/debug-vm-pgtable/arch-support.txt
 create mode 100644 mm/debug_vm_pgtable.c

-- 
2.20.1

[PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers

[Anshuman Khandual]

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.

Test page table and memory pages creating it's entries at various level are
all allocated from system memory with required size and alignments. But if
memory pages with required size and alignment could not be allocated, then
all depending individual tests are just skipped afterwards. This test gets
called right after init_mm_internals() required for alloc_contig_range() to
work correctly.

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.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Steven Price <Steven.Price@arm.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sri Krishna chowdary <schowdary@nvidia.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
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 <christophe.leroy@c-s.fr>		#PPC32
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 .../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                         | 450 ++++++++++++++++++
 9 files changed, 521 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 000000000000..d6b8185dcf1e
--- /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 |
+    |       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 950a56b71ff0..8a3b3eaa49e9 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 abe822d52167..13c9bd950256 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/x86/include/asm/pgtable_64.h b/arch/x86/include/asm/pgtable_64.h
index 0b6c4042942a..fb0e76d254b3 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 818691846c90..7f97b7a4a9e2 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -1157,6 +1157,12 @@ 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 91f6ebb30ef0..676d8020dd29 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1177,6 +1177,7 @@ static noinline void __init kernel_init_freeable(void)
 	workqueue_init();
 
 	init_mm_internals();
+	debug_vm_pgtable();
 
 	do_pre_smp_initcalls();
 	lockup_detector_init();
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cb1fc48e61e3..b9b8fe1e2180 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -698,6 +698,27 @@ 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.
+
 config ARCH_HAS_DEBUG_VIRTUAL
 	bool
 
diff --git a/mm/Makefile b/mm/Makefile
index d996846697ef..2f085b971d34 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 000000000000..24da76d8b343
--- /dev/null
+++ b/mm/debug_vm_pgtable.c
@@ -0,0 +1,450 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This kernel module validates architecture page table helpers &
+ * accessors and helps in verifying their continued compliance with
+ * generic MM semantics.
+ *
+ * Copyright (C) 2019 ARM Ltd.
+ *
+ * Author: Anshuman Khandual <anshuman.khandual@arm.com>
+ */
+#define pr_fmt(fmt) "arch_pgtable_test: %s " fmt, __func__
+
+#include <linux/gfp.h>
+#include <linux/highmem.h>
+#include <linux/hugetlb.h>
+#include <linux/kernel.h>
+#include <linux/kconfig.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/mm_types.h>
+#include <linux/module.h>
+#include <linux/pfn_t.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+#include <linux/spinlock.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/sched/mm.h>
+#include <asm/pgalloc.h>
+#include <asm/pgtable.h>
+
+/*
+ * 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 bool pud_aligned __initdata;
+static bool pmd_aligned __initdata;
+
+static void __init pte_basic_tests(struct page *page, pgprot_t prot)
+{
+	pte_t pte = mk_pte(page, 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(struct page *page, pgprot_t prot)
+{
+	pmd_t pmd;
+
+	/*
+	 * Memory block here must be PMD_SIZE aligned. Abort this
+	 * test in case we could not allocate such a memory block.
+	 */
+	if (!pmd_aligned) {
+		pr_warn("Could not proceed with PMD tests\n");
+		return;
+	}
+
+	pmd = mk_pmd(page, 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(struct page *page, pgprot_t prot) { }
+#endif
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+static void __init pud_basic_tests(struct page *page, pgprot_t prot)
+{
+	pud_t pud;
+
+	/*
+	 * Memory block here must be PUD_SIZE aligned. Abort this
+	 * test in case we could not allocate such a memory block.
+	 */
+	if (!pud_aligned) {
+		pr_warn("Could not proceed with PUD tests\n");
+		return;
+	}
+
+	pud = pfn_pud(page_to_pfn(page), 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(struct page *page, pgprot_t prot) { }
+#endif
+
+static void __init p4d_basic_tests(struct page *page, 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(struct page *page, 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));
+}
+
+#ifdef CONFIG_CONTIG_ALLOC
+static struct page * __init alloc_pud_page(gfp_t gfp_mask)
+{
+	return alloc_gigantic_page_order(get_order(PUD_SIZE), gfp_mask,
+				first_memory_node, &node_states[N_MEMORY]);
+}
+#else
+static struct page * __init alloc_pud_page(gfp_t pfp_mask)
+{
+	return NULL;
+}
+#endif
+
+static struct page * __init alloc_mapped_page(void)
+{
+	struct page *page;
+	gfp_t gfp_mask = GFP_KERNEL | __GFP_ZERO;
+
+	page = alloc_pud_page(gfp_mask);
+	if (page) {
+		pud_aligned = true;
+		pmd_aligned = true;
+		return page;
+	}
+
+	page = alloc_pages(gfp_mask, get_order(PMD_SIZE));
+	if (page) {
+		pmd_aligned = true;
+		return page;
+	}
+	return alloc_page(gfp_mask);
+}
+
+static void __init free_mapped_page(struct page *page)
+{
+	if (pud_aligned) {
+		unsigned long pfn = page_to_pfn(page);
+
+		free_contig_range(pfn, 1ULL << get_order(PUD_SIZE));
+		return;
+	}
+
+	if (pmd_aligned) {
+		int order = get_order(PMD_SIZE);
+
+		free_pages((unsigned long)page_address(page), order);
+		return;
+	}
+	free_page((unsigned long)page_address(page));
+}
+
+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);
+	WARN_ON(random_vaddr < FIRST_USER_ADDRESS);
+	return random_vaddr;
+}
+
+void __init debug_vm_pgtable(void)
+{
+	struct mm_struct *mm;
+	struct page *page;
+	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;
+	unsigned long vaddr;
+
+	prot = vm_get_page_prot(VMFLAGS);
+	vaddr = get_random_vaddr();
+	mm = mm_alloc();
+	if (!mm) {
+		pr_err("mm_struct allocation failed\n");
+		return;
+	}
+
+	page = alloc_mapped_page();
+	if (!page) {
+		pr_err("memory allocation failed\n");
+		return;
+	}
+
+	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(page, prot);
+	pmd_basic_tests(page, prot);
+	pud_basic_tests(page, prot);
+	p4d_basic_tests(page, prot);
+	pgd_basic_tests(page, 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);
+
+	free_mapped_page(page);
+}
-- 
2.20.1

Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers

[Michal Hocko]

On Tue 15-10-19 14:51:42, 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.
> 
> Test page table and memory pages creating it's entries at various level are
> all allocated from system memory with required size and alignments. But if
> memory pages with required size and alignment could not be allocated, then
> all depending individual tests are just skipped afterwards. This test gets
> called right after init_mm_internals() required for alloc_contig_range() to
> work correctly.
> 
> 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.

A highlevel description of tests and what they are testing for would be
really appreciated. Who wants to run these tests and why/when? What kind
of bugs would get detected? In short why do we really need/want this
code in the tree?

-- 
Michal Hocko
SUSE Labs

Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers

[Anshuman Khandual]

On 10/15/2019 05:16 PM, Michal Hocko wrote:
> On Tue 15-10-19 14:51:42, 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.
>>
>> Test page table and memory pages creating it's entries at various level are
>> all allocated from system memory with required size and alignments. But if
>> memory pages with required size and alignment could not be allocated, then
>> all depending individual tests are just skipped afterwards. This test gets
>> called right after init_mm_internals() required for alloc_contig_range() to
>> work correctly.
>>
>> 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.
> 
> A highlevel description of tests and what they are testing for would be
> really appreciated. Who wants to run these tests and why/when? What kind
> of bugs would get detected? In short why do we really need/want this
> code in the tree?

Sure, will do.

Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[Qian Cai]

The x86 will crash with linux-next during boot due to this series (v5) with the
config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
it.

https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config

[   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
[   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
[   33.871140][    T1]  ? rest_init+0x307/0x307
[   33.871140][    T1]  kernel_init+0x11/0x139
[   33.871140][    T1]  ? rest_init+0x307/0x307
[   33.871140][    T1]  ret_from_fork+0x27/0x50
[   33.871140][    T1] Modules linked in:
[   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
[   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490

On Tue, 2019-10-15 at 14:51 +0530, Anshuman Khandual wrote:
> This series adds a test validation for architecture exported page table
> helpers. Patch in the series adds basic transformation tests at various
> levels of the page table. Before that it exports gigantic page allocation
> function from HugeTLB.
> 
> This test was originally suggested by Catalin during arm64 THP migration
> RFC discussion earlier. Going forward it can include more specific tests
> with respect to various generic MM functions like THP, HugeTLB etc and
> platform specific tests.
> 
> https://lore.kernel.org/linux-mm/20190628102003.GA56463@arrakis.emea.arm.com/
> 
> Changes in V6:
> 
> - Moved alloc_gigantic_page_order() into mm/page_alloc.c per Michal
> - Moved alloc_gigantic_page_order() within CONFIG_CONTIG_ALLOC in the test
> - Folded Andrew's include/asm-generic/pgtable.h fix into the test patch 2/2
> 
> Changes in V5: (https://patchwork.kernel.org/project/linux-mm/list/?series=185991)
> 
> - Redefined and moved X86 mm_p4d_folded() into a different header per Kirill/Ingo
> - Updated the config option comment per Ingo and dropped 'kernel module' reference
> - Updated the commit message and dropped 'kernel module' reference
> - Changed DEBUG_ARCH_PGTABLE_TEST into DEBUG_VM_PGTABLE per Ingo
> - Moved config option from mm/Kconfig.debug into lib/Kconfig.debug
> - Renamed core test function arch_pgtable_tests() as debug_vm_pgtable()
> - Renamed mm/arch_pgtable_test.c as mm/debug_vm_pgtable.c
> - debug_vm_pgtable() gets called from kernel_init_freeable() after init_mm_internals()
> - Added an entry in Documentation/features/debug/ per Ingo
> - Enabled the test on arm64 and x86 platforms for now
> 
> Changes in V4: (https://patchwork.kernel.org/project/linux-mm/list/?series=183465)
> 
> - Disable DEBUG_ARCH_PGTABLE_TEST for ARM and IA64 platforms
> 
> Changes in V3: (https://lore.kernel.org/patchwork/project/lkml/list/?series=411216)
> 
> - Changed test trigger from module format into late_initcall()
> - Marked all functions with __init to be freed after completion
> - Changed all __PGTABLE_PXX_FOLDED checks as mm_pxx_folded()
> - Folded in PPC32 fixes from Christophe
> 
> Changes in V2:
> 
> https://lore.kernel.org/linux-mm/1568268173-31302-1-git-send-email-anshuman.khandual@arm.com/T/#t
> 
> - Fixed small typo error in MODULE_DESCRIPTION()
> - Fixed m64k build problems for lvalue concerns in pmd_xxx_tests()
> - Fixed dynamic page table level folding problems on x86 as per Kirril
> - Fixed second pointers during pxx_populate_tests() per Kirill and Gerald
> - Allocate and free pte table with pte_alloc_one/pte_free per Kirill
> - Modified pxx_clear_tests() to accommodate s390 lower 12 bits situation
> - Changed RANDOM_NZVALUE value from 0xbe to 0xff
> - Changed allocation, usage, free sequence for saved_ptep
> - Renamed VMA_FLAGS as VMFLAGS
> - Implemented a new method for random vaddr generation
> - Implemented some other cleanups
> - Dropped extern reference to mm_alloc()
> - Created and exported new alloc_gigantic_page_order()
> - Dropped the custom allocator and used new alloc_gigantic_page_order()
> 
> Changes in V1:
> 
> https://lore.kernel.org/linux-mm/1567497706-8649-1-git-send-email-anshuman.khandual@arm.com/
> 
> - Added fallback mechanism for PMD aligned memory allocation failure
> 
> Changes in RFC V2:
> 
> https://lore.kernel.org/linux-mm/1565335998-22553-1-git-send-email-anshuman.khandual@arm.com/T/#u
> 
> - Moved test module and it's config from lib/ to mm/
> - Renamed config TEST_ARCH_PGTABLE as DEBUG_ARCH_PGTABLE_TEST
> - Renamed file from test_arch_pgtable.c to arch_pgtable_test.c
> - Added relevant MODULE_DESCRIPTION() and MODULE_AUTHOR() details
> - Dropped loadable module config option
> - Basic tests now use memory blocks with required size and alignment
> - PUD aligned memory block gets allocated with alloc_contig_range()
> - If PUD aligned memory could not be allocated it falls back on PMD aligned
>   memory block from page allocator and pud_* tests are skipped
> - Clear and populate tests now operate on real in memory page table entries
> - Dummy mm_struct gets allocated with mm_alloc()
> - Dummy page table entries get allocated with [pud|pmd|pte]_alloc_[map]()
> - Simplified [p4d|pgd]_basic_tests(), now has random values in the entries
> 
> Original RFC V1:
> 
> https://lore.kernel.org/linux-mm/1564037723-26676-1-git-send-email-anshuman.khandual@arm.com/
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: Steven Price <Steven.Price@arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Sri Krishna chowdary <schowdary@nvidia.com>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Russell King - ARM Linux <linux@armlinux.org.uk>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Paul Mackerras <paulus@samba.org>
> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Vineet Gupta <vgupta@synopsys.com>
> Cc: James Hogan <jhogan@kernel.org>
> Cc: Paul Burton <paul.burton@mips.com>
> Cc: Ralf Baechle <ralf@linux-mips.org>
> Cc: Kirill A. Shutemov <kirill@shutemov.name>
> Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: Mike Kravetz <mike.kravetz@oracle.com>
> 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
> 
> 
> Anshuman Khandual (2):
>   mm/page_alloc: Make alloc_gigantic_page() available for general use
>   mm/debug: Add tests validating architecture page table helpers
> 
>  .../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 +
>  include/linux/gfp.h                           |   3 +
>  init/main.c                                   |   1 +
>  lib/Kconfig.debug                             |  21 +
>  mm/Makefile                                   |   1 +
>  mm/debug_vm_pgtable.c                         | 450 ++++++++++++++++++
>  mm/hugetlb.c                                  |  76 +--
>  mm/page_alloc.c                               |  98 ++++
>  12 files changed, 623 insertions(+), 75 deletions(-)
>  create mode 100644 Documentation/features/debug/debug-vm-pgtable/arch-support.txt
>  create mode 100644 mm/debug_vm_pgtable.c
> 

Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[Anshuman Khandual]

On 10/15/2019 08:11 PM, Qian Cai wrote:
> The x86 will crash with linux-next during boot due to this series (v5) with the
> config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
> it.
> 
> https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
> 
> [   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
> [   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
> ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
> [   33.871140][    T1]  ? rest_init+0x307/0x307
> [   33.871140][    T1]  kernel_init+0x11/0x139
> [   33.871140][    T1]  ? rest_init+0x307/0x307
> [   33.871140][    T1]  ret_from_fork+0x27/0x50
> [   33.871140][    T1] Modules linked in:
> [   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
> [   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490

Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
with the config above, it does. Just wondering if it is possible that these
pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?

[   13.898549][    T1] page:ffffea0005000000 is uninitialized and poisoned
[   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
[   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
[   13.898549][    T1] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
[   13.898549][    T1] ------------[ cut here ]------------
[   13.898549][    T1] kernel BUG at ./include/linux/mm.h:1107!
[   13.898549][    T1] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
[   13.898549][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-next-20191015+ #

Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers

[Qian Cai]

On Tue, 2019-10-15 at 14:51 +0530, Anshuman Khandual wrote:
> +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);
> +	WARN_ON(random_vaddr < FIRST_USER_ADDRESS);

It would be nice if this patch does not introduce a new W=1 GCC warning here on
x86 because FIRST_USER_ADDRESS is 0, and GCC think the code is dumb because
"random_vaddr" is unsigned,

In file included from ./arch/x86/include/asm/bug.h:83,
                 from ./include/linux/bug.h:5,
                 from ./include/linux/mmdebug.h:5,
                 from ./include/linux/gfp.h:5,
                 from mm/debug_vm_pgtable.c:13:
mm/debug_vm_pgtable.c: In function ‘get_random_vaddr’:
mm/debug_vm_pgtable.c:359:23: warning: comparison of unsigned expression < 0 is
always false [-Wtype-limits]
  WARN_ON(random_vaddr < FIRST_USER_ADDRESS);
                       ^
./include/asm-generic/bug.h:113:25: note: in definition of macro ‘WARN_ON’
  int __ret_warn_on = !!(condition);    \
                         ^~~~~~~~~

Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[Qian Cai]

On Tue, 2019-10-15 at 20:51 +0530, Anshuman Khandual wrote:
> 
> On 10/15/2019 08:11 PM, Qian Cai wrote:
> > The x86 will crash with linux-next during boot due to this series (v5) with the
> > config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
> > it.
> > 
> > https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
> > 
> > [   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
> > [   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
> > ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
> > [   33.871140][    T1]  ? rest_init+0x307/0x307
> > [   33.871140][    T1]  kernel_init+0x11/0x139
> > [   33.871140][    T1]  ? rest_init+0x307/0x307
> > [   33.871140][    T1]  ret_from_fork+0x27/0x50
> > [   33.871140][    T1] Modules linked in:
> > [   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
> > [   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490
> 
> Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
> with the config above, it does. Just wondering if it is possible that these
> pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?

Yes, this patch works fine.

diff --git a/init/main.c b/init/main.c
index 676d8020dd29..591be8f9e8e0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1177,7 +1177,6 @@ static noinline void __init kernel_init_freeable(void)
        workqueue_init();
 
        init_mm_internals();
-       debug_vm_pgtable();
 
        do_pre_smp_initcalls();
        lockup_detector_init();
@@ -1186,6 +1185,8 @@ 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();

> 
> [   13.898549][    T1] page:ffffea0005000000 is uninitialized and poisoned
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
> [   13.898549][    T1] ------------[ cut here ]------------
> [   13.898549][    T1] kernel BUG at ./include/linux/mm.h:1107!
> [   13.898549][    T1] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
> [   13.898549][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-next-20191015+ #

Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[Michal Hocko]

On Tue 15-10-19 20:51:11, Anshuman Khandual wrote:
> 
> 
> On 10/15/2019 08:11 PM, Qian Cai wrote:
> > The x86 will crash with linux-next during boot due to this series (v5) with the
> > config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
> > it.
> > 
> > https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
> > 
> > [   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
> > [   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
> > ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
> > [   33.871140][    T1]  ? rest_init+0x307/0x307
> > [   33.871140][    T1]  kernel_init+0x11/0x139
> > [   33.871140][    T1]  ? rest_init+0x307/0x307
> > [   33.871140][    T1]  ret_from_fork+0x27/0x50
> > [   33.871140][    T1] Modules linked in:
> > [   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
> > [   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490
> 
> Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
> with the config above, it does. Just wondering if it is possible that these
> pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?

Quite likely. You need to wait for page_alloc_init_late to finish.
> 
> [   13.898549][    T1] page:ffffea0005000000 is uninitialized and poisoned
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
> [   13.898549][    T1] ------------[ cut here ]------------
> [   13.898549][    T1] kernel BUG at ./include/linux/mm.h:1107!
> [   13.898549][    T1] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
> [   13.898549][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-next-20191015+ #

-- 
Michal Hocko
SUSE Labs

Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers

[Anshuman Khandual]

On 10/16/2019 12:12 AM, Qian Cai wrote:
> On Tue, 2019-10-15 at 20:51 +0530, Anshuman Khandual wrote:
>>
>> On 10/15/2019 08:11 PM, Qian Cai wrote:
>>> The x86 will crash with linux-next during boot due to this series (v5) with the
>>> config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
>>> it.
>>>
>>> https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
>>>
>>> [   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
>>> [   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
>>> ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
>>> [   33.871140][    T1]  ? rest_init+0x307/0x307
>>> [   33.871140][    T1]  kernel_init+0x11/0x139
>>> [   33.871140][    T1]  ? rest_init+0x307/0x307
>>> [   33.871140][    T1]  ret_from_fork+0x27/0x50
>>> [   33.871140][    T1] Modules linked in:
>>> [   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
>>> [   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490
>>
>> Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
>> with the config above, it does. Just wondering if it is possible that these
>> pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?
> 
> Yes, this patch works fine.
> 
> diff --git a/init/main.c b/init/main.c
> index 676d8020dd29..591be8f9e8e0 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -1177,7 +1177,6 @@ static noinline void __init kernel_init_freeable(void)
>         workqueue_init();
>  
>         init_mm_internals();
> -       debug_vm_pgtable();
>  
>         do_pre_smp_initcalls();
>         lockup_detector_init();
> @@ -1186,6 +1185,8 @@ 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();
> 

Sure, will keep this in mind if we at all end up with memory allocation approach
for this test.

>>
>> [   13.898549][    T1] page:ffffea0005000000 is uninitialized and poisoned
>> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
>> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
>> [   13.898549][    T1] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
>> [   13.898549][    T1] ------------[ cut here ]------------
>> [   13.898549][    T1] kernel BUG at ./include/linux/mm.h:1107!
>> [   13.898549][    T1] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
>> [   13.898549][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-next-20191015+ #
> 

Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers

[Anshuman Khandual]

On 10/15/2019 11:39 PM, Qian Cai wrote:
> On Tue, 2019-10-15 at 14:51 +0530, Anshuman Khandual wrote:
>> +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);
>> +	WARN_ON(random_vaddr < FIRST_USER_ADDRESS);
> 
> It would be nice if this patch does not introduce a new W=1 GCC warning here on
> x86 because FIRST_USER_ADDRESS is 0, and GCC think the code is dumb because
> "random_vaddr" is unsigned,
> 
> In file included from ./arch/x86/include/asm/bug.h:83,
>                  from ./include/linux/bug.h:5,
>                  from ./include/linux/mmdebug.h:5,
>                  from ./include/linux/gfp.h:5,
>                  from mm/debug_vm_pgtable.c:13:
> mm/debug_vm_pgtable.c: In function ‘get_random_vaddr’:
> mm/debug_vm_pgtable.c:359:23: warning: comparison of unsigned expression < 0 is
> always false [-Wtype-limits]
>   WARN_ON(random_vaddr < FIRST_USER_ADDRESS);
>                        ^
> ./include/asm-generic/bug.h:113:25: note: in definition of macro ‘WARN_ON’
>   int __ret_warn_on = !!(condition);    \
>                          ^~~~~~~~~

The test checks against an erroneous unsigned long overflow when
FIRST_USER_ADDRESS is not 0 but a positive number. Wondering if
the compiler will still complain if we merge both the WARN_ON()
checks as || on a single statement.