Le 28/01/2020 à 02:27, Anshuman Khandual a écrit :
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.
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Tested-by: Christophe Leroy <christophe.leroy@xxxxxx> #PPC32
Also tested on PPC64 (under QEMU): book3s/64 64k pages, book3s/64 4k pages and book3e/64
Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx> Suggested-by: Catalin Marinas <catalin.marinas@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> ---
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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..f3f8111edbe3 --- /dev/null +++ b/Documentation/features/debug/debug-vm-pgtable/arch-support.txt @@ -0,0 +1,35 @@ +# +# Feature name: debug-vm-pgtable +# Kconfig: ARCH_HAS_DEBUG_VM_PGTABLE +# description: arch supports pgtable tests for semantics compliance +# + ----------------------- + | arch |status| + ----------------------- + | alpha: | TODO | + | arc: | ok | + | 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/32: | ok | + | powerpc/64: | TODO |
You can change the two above lines by powerpc: ok
+ | riscv: | TODO | + | s390: | TODO | + | sh: | TODO | + | sparc: | TODO | + | um: | TODO | + | unicore32: | TODO | + | x86: | ok | + | xtensa: | TODO | + -----------------------
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 1ec34e16ed65..253dcab0bebc 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
Remove the 'if PPC32' as we now know it also work on PPC64.
select ARCH_HAS_DEVMEM_IS_ALLOWED select ARCH_HAS_ELF_RANDOMIZE select ARCH_HAS_FORTIFY_SOURCE
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(); +} +
For me this should be part of another patch, it is not directly linked to the tests.
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.hindex 798ea36a0549..e0b04787e789 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -1208,6 +1208,12 @@ static inline bool arch_has_pfn_modify_check(void) # define PAGE_KERNEL_EXEC PAGE_KERNEL #endif+#ifdef CONFIG_DEBUG_VM_PGTABLE
Not sure it is a good idea to put that in include/asm-generic/pgtable.hBy doing this you are forcing a rebuild of almost all files, whereas only init/main.o and mm/debug_vm_pgtable.o should be rebuilt when activating this config option.
+extern void debug_vm_pgtable(void);
Please don't use the 'extern' keyword, it is useless and not to be used for functions declaration.
+#else +static inline void debug_vm_pgtable(void) { } +#endif + #endif /* !__ASSEMBLY__ */#ifndef io_remap_pfn_rangediff --git a/init/main.c b/init/main.c index da1bc0b60a7d..5e59e6ac0780 100644 --- a/init/main.c +++ b/init/main.c @@ -1197,6 +1197,7 @@ static noinline void __init kernel_init_freeable(void) sched_init_smp();page_alloc_init_late();+ debug_vm_pgtable();
Wouldn't it be better to call debug_vm_pgtable() in kernel_init() between the call to async_synchronise_full() and ftrace_free_init_mem() ?
/* Initialize page ext after all struct pages are initialized. */ page_ext_init();diff --git a/lib/Kconfig.debug b/lib/Kconfig.debugindex 5ffe144c9794..7cceae923c05 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -653,6 +653,12 @@ config SCHED_STACK_END_CHECK data corruption or a sporadic crash at a later stage once the region is examined. The runtime overhead introduced is minimal.+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 bool "Debug VM" depends on DEBUG_KERNEL @@ -688,6 +694,22 @@ config DEBUG_VM_PGFLAGSIf unsure, say N. +config DEBUG_VM_PGTABLE+ bool "Debug arch page table for semantics compliance" + depends on MMU + depends on DEBUG_VM
Does it really need to depend on DEBUG_VM ? I think we could make it standalone and 'default y if DEBUG_VM' instead.
+ depends on ARCH_HAS_DEBUG_VM_PGTABLE + default y + 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. +
Does it make sense to make it 'default y' and say 'If unsure, say N' ?
config ARCH_HAS_DEBUG_VIRTUAL bool
Christophe
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