Re: [PATCH v2 2/2] memblock: do not start bottom-up allocations with kernel_end
From: Mike Rapoport
Date: Sun Feb 28 2021 - 04:07:19 EST
Hi Florian,
On Sat, Feb 27, 2021 at 08:18:47PM -0800, Florian Fainelli wrote:
>
> On 12/17/2020 12:12 PM, Roman Gushchin wrote:
> > 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:
> >
> > [ 0.002920] hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node
> > [ 0.002921] ------------[ cut here ]------------
> > [ 0.002922] memblock: bottom-up allocation failed, memory hotremove may be affected
> > [ 0.002937] WARNING: CPU: 0 PID: 0 at mm/memblock.c:332 memblock_find_in_range_node+0x178/0x25a
> > [ 0.002937] Modules linked in:
> > [ 0.002939] CPU: 0 PID: 0 Comm: swapper Not tainted 5.10.0+ #1169
> > [ 0.002940] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
> > [ 0.002942] RIP: 0010:memblock_find_in_range_node+0x178/0x25a
> > [ 0.002944] 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
> > [ 0.002945] RSP: 0000:ffffffff88803d18 EFLAGS: 00010086 ORIG_RAX: 0000000000000000
> > [ 0.002947] RAX: 0000000000000000 RBX: 0000000240000000 RCX: 00000000ffffdfff
> > [ 0.002948] RDX: 00000000ffffdfff RSI: 00000000ffffffea RDI: 0000000000000046
> > [ 0.002948] RBP: 0000000100000000 R08: ffffffff88922788 R09: 0000000000009ffb
> > [ 0.002949] R10: 00000000ffffe000 R11: 3fffffffffffffff R12: 0000000000000000
> > [ 0.002950] R13: 0000000000000000 R14: 0000000080000000 R15: 00000001fb42c000
> > [ 0.002952] FS: 0000000000000000(0000) GS:ffffffff88f71000(0000) knlGS:0000000000000000
> > [ 0.002953] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 0.002954] CR2: ffffa080fb401000 CR3: 00000001fa80a000 CR4: 00000000000406b0
> > [ 0.002956] Call Trace:
> > [ 0.002961] ? memblock_alloc_range_nid+0x8d/0x11e
> > [ 0.002963] ? cma_declare_contiguous_nid+0x2c4/0x38c
> > [ 0.002964] ? hugetlb_cma_reserve+0xdc/0x128
> > [ 0.002968] ? flush_tlb_one_kernel+0xc/0x20
> > [ 0.002969] ? native_set_fixmap+0x82/0xd0
> > [ 0.002971] ? flat_get_apic_id+0x5/0x10
> > [ 0.002973] ? register_lapic_address+0x8e/0x97
> > [ 0.002975] ? setup_arch+0x8a5/0xc3f
> > [ 0.002978] ? start_kernel+0x66/0x547
> > [ 0.002980] ? load_ucode_bsp+0x4c/0xcd
> > [ 0.002982] ? secondary_startup_64_no_verify+0xb0/0xbb
> > [ 0.002986] random: get_random_bytes called from __warn+0xab/0x110 with crng_init=0
> > [ 0.002988] ---[ 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.
> >
> > Signed-off-by: Roman Gushchin <guro@xxxxxx>
>
> Hi Roman, Thomas and other linux-mips folks,
>
> Kamal and myself have been unable to boot v5.11 on MIPS since this
> commit, reverting it makes our MIPS platforms boot successfully. We do
> not see a warning like this one in the commit message, instead what
> happens appear to be a corrupted Device Tree which prevents the parsing
> of the "rdb" node and leading to the interrupt controllers not being
> registered, and the system eventually not booting.
>
> The Device Tree is built-into the kernel image and resides at
> arch/mips/boot/dts/brcm/bcm97435svmb.dts.
>
> Do you have any idea what could be wrong with MIPS specifically here?
Apparently there is a memblock allocation in one of the functions called
from arch_mem_init() between plat_mem_setup() and
early_init_fdt_reserve_self().
If you have serial available that early we can try to track it down with
forcing memblock_debug in mm/memblock.c to 1:
diff --git a/mm/memblock.c b/mm/memblock.c
index afaefa8fc6ab..83034245f8d5 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -151,7 +151,7 @@ static __refdata struct memblock_type *memblock_memory = &memblock.memory;
pr_info(fmt, ##__VA_ARGS__); \
} while (0)
-static int memblock_debug __initdata_memblock;
+static int memblock_debug __initdata_memblock = 1;
static bool system_has_some_mirror __initdata_memblock = false;
static int memblock_can_resize __initdata_memblock;
static int memblock_memory_in_slab __initdata_memblock = 0;
Regardless, I think that moving DT self reservation just after
plat_mem_setup() is safe and it'll make things more robust.
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 279be0153f8b..f476b99a7bcd 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -623,6 +623,8 @@ static void __init arch_mem_init(char **cmdline_p)
{
/* call board setup routine */
plat_mem_setup();
+ early_init_fdt_reserve_self();
+ early_init_fdt_scan_reserved_mem();
memblock_set_bottom_up(true);
bootcmdline_init();
@@ -636,9 +638,6 @@ static void __init arch_mem_init(char **cmdline_p)
check_kernel_sections_mem();
- early_init_fdt_reserve_self();
- early_init_fdt_scan_reserved_mem();
-
#ifndef CONFIG_NUMA
memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
#endif
--
Sincerely yours,
Mike.