[patch 096/262] vmalloc: choose a better start address in vm_area_register_early()

Andrew Morton
2021-11-05T20:39:44Z

From: Kefeng Wang <wangkefeng.wang@huawei.com>
Subject: vmalloc: choose a better start address in vm_area_register_early()

Percpu embedded first chunk allocator is the firstly option, but it could
fail on ARM64, eg,

"percpu: max_distance=0x5fcfdc640000 too large for vmalloc space 0x781fefff0000"
"percpu: max_distance=0x600000540000 too large for vmalloc space 0x7dffb7ff0000"
"percpu: max_distance=0x5fff9adb0000 too large for vmalloc space 0x5dffb7ff0000"

then we could meet "WARNING: CPU: 15 PID: 461 at vmalloc.c:3087
pcpu_get_vm_areas+0x488/0x838" and the system cannot boot successfully.

Let's implement page mapping percpu first chunk allocator as a fallback to
the embedding allocator to increase the robustness of the system.

Also fix a crash when both NEED_PER_CPU_PAGE_FIRST_CHUNK and KASAN_VMALLOC
enabled.

Tested on ARM64 qemu with cmdline "percpu_alloc=page".

This patch (of 3):

There are some fixed locations in the vmalloc area be reserved in ARM(see
iotable_init()) and ARM64(see map_kernel()), but for
pcpu_page_first_chunk(), it calls vm_area_register_early() and choose
VMALLOC_START as the start address of vmap area which could be conflicted
with above address, then could trigger a BUG_ON in vm_area_add_early().

Let's choose a suit start address by traversing the vmlist.

Link: https://lkml.kernel.org/r/20210910053354.26721-1-wangkefeng.wang@huawei.com
Link: https://lkml.kernel.org/r/20210910053354.26721-2-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/vmalloc.c | 18 ++++++++++++------
1 file changed, 12 insertions(+), 6 deletions(-)

--- a/mm/vmalloc.c~vmalloc-choose-a-better-start-address-in-vm_area_register_early
+++ a/mm/vmalloc.c
@@ -2276,15 +2276,21 @@ void __init vm_area_add_early(struct vm_
*/
void __init vm_area_register_early(struct vm_struct *vm, size_t align)
{
- static size_t vm_init_off __initdata;
- unsigned long addr;
+ unsigned long addr = ALIGN(VMALLOC_START, align);
+ struct vm_struct *cur, **p;

- addr = ALIGN(VMALLOC_START + vm_init_off, align);
- vm_init_off = PFN_ALIGN(addr + vm->size) - VMALLOC_START;
+ BUG_ON(vmap_initialized);

- vm->addr = (void *)addr;
+ for (p = &vmlist; (cur = *p) != NULL; p = &cur->next) {
+ if ((unsigned long)cur->addr - addr >= vm->size)
+ break;
+ addr = ALIGN((unsigned long)cur->addr + cur->size, align);
+ }

- vm_area_add_early(vm);
+ BUG_ON(addr > VMALLOC_END - vm->size);
+ vm->addr = (void *)addr;
+ vm->next = *p;
+ *p = vm;
}

static void vmap_init_free_space(void)
_