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memblock: do not start bottom-up allocations with kernel_end

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With kaslr the kernel image is placed at a random place, so starting the
bottom-up allocation with the kernel_end can result in an allocation
failure and a warning like this one:

  hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node
  ------------[ cut here ]------------
  memblock: bottom-up allocation failed, memory hotremove may be affected
  WARNING: CPU: 0 PID: 0 at mm/memblock.c:332 memblock_find_in_range_node+0x178/0x25a
  Modules linked in:
  CPU: 0 PID: 0 Comm: swapper Not tainted 5.10.0+ #1169
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
  RIP: 0010:memblock_find_in_range_node+0x178/0x25a
  Code: e9 6d ff ff ff 48 85 c0 0f 85 da 00 00 00 80 3d 9b 35 df 00 00 75 15 48 c7 c7 c0 75 59 88 c6 05 8b 35 df 00 01 e8 25 8a fa ff <0f> 0b 48 c7 44 24 20 ff ff ff ff 44 89 e6 44 89 ea 48 c7 c1 70 5c
  RSP: 0000:ffffffff88803d18 EFLAGS: 00010086 ORIG_RAX: 0000000000000000
  RAX: 0000000000000000 RBX: 0000000240000000 RCX: 00000000ffffdfff
  RDX: 00000000ffffdfff RSI: 00000000ffffffea RDI: 0000000000000046
  RBP: 0000000100000000 R08: ffffffff88922788 R09: 0000000000009ffb
  R10: 00000000ffffe000 R11: 3fffffffffffffff R12: 0000000000000000
  R13: 0000000000000000 R14: 0000000080000000 R15: 00000001fb42c000
  FS:  0000000000000000(0000) GS:ffffffff88f71000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: ffffa080fb401000 CR3: 00000001fa80a000 CR4: 00000000000406b0
  Call Trace:
    memblock_alloc_range_nid+0x8d/0x11e
    cma_declare_contiguous_nid+0x2c4/0x38c
    hugetlb_cma_reserve+0xdc/0x128
    flush_tlb_one_kernel+0xc/0x20
    native_set_fixmap+0x82/0xd0
    flat_get_apic_id+0x5/0x10
    register_lapic_address+0x8e/0x97
    setup_arch+0x8a5/0xc3f
    start_kernel+0x66/0x547
    load_ucode_bsp+0x4c/0xcd
    secondary_startup_64_no_verify+0xb0/0xbb
  random: get_random_bytes called from __warn+0xab/0x110 with crng_init=0
  ---[ end trace f151227d0b39be70 ]---

At the same time, the kernel image is protected with memblock_reserve(),
so we can just start searching at PAGE_SIZE.  In this case the bottom-up
allocation has the same chances to success as a top-down allocation, so
there is no reason to fallback in the case of a failure.  All together it
simplifies the logic.

Link: https://lkml.kernel.org/r/20201217201214.3414100-2-guro@fb.com
Fixes: 8fabc62323 ("powerpc: Ensure that swiotlb buffer is allocated from low memory")
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Mike Rapoport <rppt@linux.ibm.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Wonhyuk Yang <vvghjk1234@gmail.com>
Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roman Gushchin 2021-02-04 18:32:36 -08:00 committed by Linus Torvalds
parent 1c2f67308a
commit 2dcb396454
1 changed files with 6 additions and 43 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

49
mm/memblock.c
View file

@ -275,14 +275,6 @@ __memblock_find_range_top_down(phys_addr_t start, phys_addr_t end,
*
* Find @size free area aligned to @align in the specified range and node.
*
* When allocation direction is bottom-up, the @start should be greater
* than the end of the kernel image. Otherwise, it will be trimmed. The
* reason is that we want the bottom-up allocation just near the kernel
* image so it is highly likely that the allocated memory and the kernel
* will reside in the same node.
*
* If bottom-up allocation failed, will try to allocate memory top-down.
*
* Return:
* Found address on success, 0 on failure.
*/
@ -291,8 +283,6 @@ static phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size,
phys_addr_t end, int nid,
enum memblock_flags flags)
{
phys_addr_t kernel_end, ret;
/* pump up @end */
if (end == MEMBLOCK_ALLOC_ACCESSIBLE ||
end == MEMBLOCK_ALLOC_KASAN)
@ -301,40 +291,13 @@ static phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size,
/* avoid allocating the first page */
start = max_t(phys_addr_t, start, PAGE_SIZE);
end = max(start, end);
kernel_end = __pa_symbol(_end);
/*
* try bottom-up allocation only when bottom-up mode
* is set and @end is above the kernel image.
*/
if (memblock_bottom_up() && end > kernel_end) {
phys_addr_t bottom_up_start;
/* make sure we will allocate above the kernel */
bottom_up_start = max(start, kernel_end);
/* ok, try bottom-up allocation first */
ret = __memblock_find_range_bottom_up(bottom_up_start, end,
size, align, nid, flags);
if (ret)
return ret;
/*
* we always limit bottom-up allocation above the kernel,
* but top-down allocation doesn't have the limit, so
* retrying top-down allocation may succeed when bottom-up
* allocation failed.
*
* bottom-up allocation is expected to be fail very rarely,
* so we use WARN_ONCE() here to see the stack trace if
* fail happens.
*/
WARN_ONCE(IS_ENABLED(CONFIG_MEMORY_HOTREMOVE),
"memblock: bottom-up allocation failed, memory hotremove may be affected\n");
}
return __memblock_find_range_top_down(start, end, size, align, nid,
flags);
if (memblock_bottom_up())
return __memblock_find_range_bottom_up(start, end, size, align,
nid, flags);
else
return __memblock_find_range_top_down(start, end, size, align,
nid, flags);
}
/**