Re: [PATCH RFC 02/20] ctlv: Add the UAPI wire format and family API

[Jiri Pirko]

Mon, Oct 26, 2026 at 07:55:12PM +0100, yeoreum.yun@xxxxxxx wrote:
>Hi,
>
>> From: Jiri Pirko <jiri@xxxxxxxxxx>

[..]

>> +#define CTLV_MAX_NEST_DEPTH		32
>
>JFYI, when I tested with CTLV_MAX_NEST_DEPTH as 32 and try to run
>ctlv_msg_test_as_deep_as_the_core_allows() message_kunit.c test,
>It experiences the *real stack overflow* on FVP
>(lesser value (e.g. 16) is fine):
>
>[    3.834419]     ok 22 ctlv_msg_test_the_bit_where_it_means_nothing
>[    3.836499]     ok 23 ctlv_msg_test_a_bit_no_version_declares
>[    3.837852] Insufficient stack space to handle exception!
>[    3.837875] ESR: 0x0000000096000047 -- DABT (current EL)
>[    3.837916] FAR: 0xffff800084efffe0
>[    3.837953] Task stack:     [0xffff800084f00000..0xffff800084f04000]
>[    3.838001] IRQ stack:      [0xffff800083d50000..0xffff800083d54000]
>[    3.838049] Overflow stack: [0xffff00087b7c3150..0xffff00087b7c4150]
>[    3.838114] CPU: 7 UID: 0 PID: 257 Comm: kunit_try_catch Tainted: G                 N
>** replaying previous printk message **
>[    3.838114] CPU: 7 UID: 0 PID: 257 Comm: kunit_try_catch Tainted: G                 N  7.3.0-rc4+ #1216 PREEMPTLAZY
>[    3.838219] Tainted: [N]=TEST
>[    3.838249] Hardware name:  , BIOS
>[    3.838279] pstate: 21400009 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
>[    3.838360] pc : __kmalloc_flags_noprof+0x10/0x540
>[    3.838433] lr : __alloc_empty_sheaf+0x48/0x88
>[    3.838501] sp : ffff800084efffa0
>[    3.838534] x29: ffff800084f00030 x28: 0000000000000400 x27: 0000000000000400
>[    3.838657] x26: ffff000803d721c0 x25: 0000000000000000 x24: 0000000000400cc0
>[    3.838780] x23: ffff00087b7e3398 x22: 16e0800080564b98 x21: ffff0008000a0900
>[    3.838908] x20: 0000000000000000 x19: ffff000800013600 x18: 0000000000000000
>[    3.839029] x17: 0000000000000001 x16: 0000000000000002 x15: ffffffff00000001
>[    3.839150] x14: 0000001c000001c0 x13: ffffffff00000001 x12: ffff000800013500
>[    3.839275] x11: ffff00080370a800 x10: 0000000000000060 x9 : ffff8000805627d0
>[    3.839401] x8 : 0000000000000000 x7 : ffffffff00000001 x6 : 0000001d000001d0
>[    3.839521] x5 : ffff800080567b68 x4 : 00000000ffffffff x3 : 0000000000000004
>[    3.839640] x2 : 0000000000000dc0 x1 : 0000000000000008 x0 : 0000000000000080
>[    3.839761] Kernel panic - not syncing: kernel stack overflow
>[    3.841533] CPU: 7 UID: 0 PID: 257 Comm: kunit_try_catch Tainted: G                 N  7.3.0-rc4+ #1216 PREEMPTLAZY
>[    3.841783] Tainted: [N]=TEST
>[    3.841877] Hardware name:  , BIOS
>[    3.841980] Call trace:
>[    3.842065]  show_stack+0x20/0x40 (C)
>[    3.842246]  __dump_stack+0x28/0x48
>[    3.842427]  dump_stack_lvl+0x28/0xb0
>[    3.842609]  dump_stack+0x18/0x34
>[    3.842788]  vpanic+0x208/0x5b8
>[    3.842944]  panic+0x54/0x60
>[    3.843096]  nmi_panic+0xc0/0xc8
>[    3.843273]  panic_bad_stack+0x10c/0x128
>[    3.843466]  handle_bad_stack+0x34/0x38
>[    3.843622]  __bad_stack+0x98/0xa0
>[    3.843773]  __kmalloc_flags_noprof+0x10/0x540 (P)
>[    3.843950]  __pcs_replace_empty_main+0x2ac/0x3e8
>[    3.844139]  __kmalloc_node_track_caller_noprof+0x440/0x520
>[    3.844328]  krealloc_node_align_noprof+0x178/0x390
>[    3.844509]  kvrealloc_node_align_noprof+0x98/0x130
>[    3.844690]  ctlv_schema_index_scope_add+0xb0/0x3f8
>[    3.844882]  ctlv_schema_check_indexed_nest+0x1e8/0x958
>
>(repeat ctlv_schema_check_attr()/ctlv_schema_check_indexed_nest())
>
>[    3.856919]  ctlv_schema_check_attr+0x3dc/0x538
>[    3.857105]  ctlv_schema_check_indexed_nest+0x788/0x958
>[    3.857301]  ctlv_schema_validate+0x88/0x180
>[    3.857482]  ctlv_msg_test_as_deep_as_the_core_allows+0x11c/0x1e8
>[    3.857698]  kunit_try_run_case+0x64/0x188
>[    3.857878]  kunit_generic_run_threadfn_adapter+0x30/0x68
>[    3.858086]  kthread+0x10c/0x140
>[    3.858245]  ret_from_fork+0x10/0x20
>[    3.858398] SMP: stopping secondary CPUs
>[    3.858630] Kernel Offset: disabled
>[    3.858720] CPU features: 0x0,00000000,00b0802e,9f190bc3,2affe72f
>[    3.858872] Memory Limit: none
>[    3.858976] ---[ end Kernel panic - not syncing: kernel stack overflow ]---
>
>[...]
>
>I think it might be good to configurable according to architecture
>unless it's not good to reduce the CTLV_MAX_NEST_DEPTH number
>otherwise, increasing stack size when CTLV is enabled seems unresonable...

Agreed, will lower it down. I think we should be okay with 8 for start.