> On Mar 29, 2022, at 11:39 AM, Edgecombe, Rick P <rick.p.edgecombe@xxxxxxxxx> wrote: > > CC some vmalloc folks. What happened was vmalloc huge pages was turned > on for x86 with the rest of the kernel unprepared and problems have > popped up. We are discussing a possible new config and vmap flag such > that for some arch's, huge pages would only be used for certain > allocations such as BPF's. > > Thread: > > https://lore.kernel.org/lkml/6080EC28-E3FE-4B00-B94A-ED7EBA1F55ED@xxxxxx/ > > On Tue, 2022-03-29 at 08:23 +0000, Song Liu wrote: >>> On Mar 28, 2022, at 5:18 PM, Edgecombe, Rick P < >>> rick.p.edgecombe@xxxxxxxxx> wrote: >>> >>> On Mon, 2022-03-28 at 23:27 +0000, Song Liu wrote: >>>> I like this direction. But I am afraid this is not enough. Using >>>> VM_NO_HUGE_VMAP in module_alloc() will make sure we don't >>>> allocate >>>> huge pages for modules. But other users of >>>> __vmalloc_node_range(), >>>> such as vzalloc in Paul's report, may still hit the issue. >>>> >>>> Maybe we need another flag VM_FORCE_HUGE_VMAP that bypasses >>>> vmap_allow_huge check. Something like the diff below. >>>> >>>> Would this work? >>> >>> Yea, that looks like a safer direction. It's too bad we can't have >>> automatic large pages, but it doesn't seem ready to just turn on >>> for >>> the whole x86 kernel. >>> >>> I'm not sure about this implementation though. It would let large >>> pages >>> get enabled without HAVE_ARCH_HUGE_VMALLOC and also despite the >>> disable >>> kernel parameter. >>> >>> Apparently some architectures can handle large pages automatically >>> and >>> it has benefits for them, so maybe vmalloc should support both >>> behaviors based on config. Like there should a >>> ARCH_HUGE_VMALLOC_REQUIRE_FLAG config. If configured it requires >>> VM_HUGE_VMAP (or some name). I don't think FORCE fits, because the >>> current logic would not always give huge pages. >>> >>> But yea, seems risky to leave it on generally, even if you could >>> fix >>> Paul's specific issue. >>> >> >> >> How about something like the following? (I still need to fix >> something, but >> would like some feedbacks on the API). >> >> Thanks, >> Song >> >> >> diff --git a/arch/Kconfig b/arch/Kconfig >> index 84bc1de02720..defef50ff527 100644 >> --- a/arch/Kconfig >> +++ b/arch/Kconfig >> @@ -858,6 +858,15 @@ config HAVE_ARCH_HUGE_VMALLOC >> depends on HAVE_ARCH_HUGE_VMAP >> bool >> >> +# >> +# HAVE_ARCH_HUGE_VMALLOC_FLAG allows users of __vmalloc_node_range >> to allocate >> +# huge page without HAVE_ARCH_HUGE_VMALLOC. To allocate huge pages,, >> the user >> +# need to call __vmalloc_node_range with VM_PREFER_HUGE_VMAP. >> +# >> +config HAVE_ARCH_HUGE_VMALLOC_FLAG >> + depends on HAVE_ARCH_HUGE_VMAP >> + bool >> + >> config ARCH_WANT_HUGE_PMD_SHARE >> bool >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index 7340d9f01b62..e64f00415575 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -161,7 +161,7 @@ config X86 >> select HAVE_ALIGNED_STRUCT_PAGE if SLUB >> select HAVE_ARCH_AUDITSYSCALL >> select HAVE_ARCH_HUGE_VMAP if X86_64 || X86_PAE >> - select HAVE_ARCH_HUGE_VMALLOC if X86_64 >> + select HAVE_ARCH_HUGE_VMALLOC_FLAG if X86_64 >> select HAVE_ARCH_JUMP_LABEL >> select HAVE_ARCH_JUMP_LABEL_RELATIVE >> select HAVE_ARCH_KASAN if X86_64 >> diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h >> index 3b1df7da402d..98f8a93fcfd4 100644 >> --- a/include/linux/vmalloc.h >> +++ b/include/linux/vmalloc.h >> @@ -35,6 +35,11 @@ struct notifier_block; /* in >> notifier.h */ >> #define VM_DEFER_KMEMLEAK 0 >> #endif >> >> +#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC_FLAG >> +#define VM_PREFER_HUGE_VMAP 0x00001000 /* prefer PMD_SIZE >> mapping (bypass vmap_allow_huge check) */ > > I don't think we should tie this to vmap_allow_huge by definition. > Also, what it does is try 2MB pages for allocations larger than 2MB. > For smaller allocations it doesn't try or "prefer" them. How about something like: #define VM_TRY_HUGE_VMAP 0x00001000 /* try PMD_SIZE mapping if size-per-node >= PMD_SIZE */ > >> +#else >> +#define VM_PREFER_HUGE_VMAP 0 >> +#endif >> /* bits [20..32] reserved for arch specific ioremap internals */ >> >> /* >> @@ -51,7 +56,7 @@ struct vm_struct { >> unsigned long size; >> unsigned long flags; >> struct page **pages; >> -#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC >> +#if (defined(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || >> defined(CONFIG_HAVE_ARCH_HUGE_VMALLOC_FLAG)) >> unsigned int page_order; >> #endif >> unsigned int nr_pages; >> @@ -225,7 +230,7 @@ static inline bool is_vm_area_hugepages(const >> void *addr) >> * prevents that. This only indicates the size of the physical >> page >> * allocated in the vmalloc layer. >> */ >> -#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC >> +#if (defined(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || >> defined(CONFIG_HAVE_ARCH_HUGE_VMALLOC_FLAG)) >> return find_vm_area(addr)->page_order > 0; >> #else >> return false; >> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c >> index 13e9dbeeedf3..fc9dae095079 100644 >> --- a/kernel/bpf/core.c >> +++ b/kernel/bpf/core.c >> @@ -851,13 +851,28 @@ static LIST_HEAD(pack_list); >> #define BPF_HPAGE_MASK PAGE_MASK >> #endif >> >> +static void *bpf_prog_pack_vmalloc(unsigned long size) >> +{ >> +#if defined(MODULES_VADDR) >> + unsigned long start = MODULES_VADDR; >> + unsigned long end = MODULES_END; >> +#else >> + unsigned long start = VMALLOC_START; >> + unsigned long end = VMALLOC_END; >> +#endif >> + >> + return __vmalloc_node_range(size, PAGE_SIZE, start, end, >> GFP_KERNEL, PAGE_KERNEL, >> + VM_DEFER_KMEMLEAK | >> VM_PREFER_HUGE_VMAP, >> + NUMA_NO_NODE, >> __builtin_return_address(0)); >> +} >> + >> static size_t select_bpf_prog_pack_size(void) >> { >> size_t size; >> void *ptr; >> >> size = BPF_HPAGE_SIZE * num_online_nodes(); >> - ptr = module_alloc(size); >> + ptr = bpf_prog_pack_vmalloc(size); >> >> /* Test whether we can get huge pages. If not just use >> PAGE_SIZE >> * packs. >> @@ -881,7 +896,7 @@ static struct bpf_prog_pack *alloc_new_pack(void) >> GFP_KERNEL); >> if (!pack) >> return NULL; >> - pack->ptr = module_alloc(bpf_prog_pack_size); >> + pack->ptr = bpf_prog_pack_vmalloc(bpf_prog_pack_size); >> if (!pack->ptr) { >> kfree(pack); >> return NULL; >> diff --git a/mm/vmalloc.c b/mm/vmalloc.c >> index e163372d3967..9d3c1ab8bdf1 100644 >> --- a/mm/vmalloc.c >> +++ b/mm/vmalloc.c >> @@ -2261,7 +2261,7 @@ static inline unsigned int >> vm_area_page_order(struct vm_struct *vm) >> >> static inline void set_vm_area_page_order(struct vm_struct *vm, >> unsigned int order) >> { >> -#ifdef CONFIG_HAVE_ARCH_HUGE_VMALLOC >> +#if (defined(CONFIG_HAVE_ARCH_HUGE_VMALLOC) || >> defined(CONFIG_HAVE_ARCH_HUGE_VMALLOC_FLAG)) >> vm->page_order = order; >> #else >> BUG_ON(order != 0); >> @@ -3106,7 +3106,8 @@ void *__vmalloc_node_range(unsigned long size, >> unsigned long align, >> return NULL; >> } >> >> - if (vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP)) { >> + if ((vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP)) || >> + (IS_ENABLED(CONFIG_HAVE_ARCH_HUGE_VMALLOC_FLAG) && >> (vm_flags & VM_PREFER_HUGE_VMAP))) { > > vmap_allow_huge is how the kernel parameter that can disable vmalloc > huge pages works. I don't think we should separate it. Disabling > vmalloc huge pages should still disable this alternate mode. Yeah, this makes sense. I will fix it. > >> unsigned long size_per_node; >> >> /*
