Re: [PATCH v9 bpf-next 1/9] x86/Kconfig: select HAVE_ARCH_HUGE_VMALLOC with HAVE_ARCH_HUGE_VMAP

[Song Liu <songliubraving@fb.com>]

> On Mar 28, 2022, at 5:18 PM, Edgecombe, Rick P <rick.p.edgecombe@intel.com> 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) */
+#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))) {
 		unsigned long size_per_node;
 
 		/*