On Tue, Oct 17, 2023 at 01:34:18PM +0530, Naresh Kamboju wrote: > Following kernel crash noticed while running selftests: ftrace: > ftracetest-ktap on FVP models running stable-rc 6.5.8-rc2. > This is not an easy to reproduce issue and not seen on mainline and next. > We are investigating this report. To confirm have you seen this on other stables as well or is this only v6.5? For how long have you been seeing this? > [ 764.987161] Unable to handle kernel NULL pointer dereference at > virtual address 0000000000000000 > [ 765.074221] Call trace: > [ 765.075045] sve_save_state+0x4/0xf0 > [ 765.076138] fpsimd_thread_switch+0x2c/0xe8 > [ 765.077305] __switch_to+0x20/0x158 > [ 765.078384] __schedule+0x2cc/0xb38 > [ 765.079464] preempt_schedule_irq+0x44/0xa8 > [ 765.080633] el1_interrupt+0x4c/0x68 > [ 765.081691] el1h_64_irq_handler+0x18/0x28 > [ 765.082829] el1h_64_irq+0x64/0x68 > [ 765.083874] ftrace_return_to_handler+0x98/0x158 > [ 765.085090] return_to_handler+0x20/0x48 > [ 765.086205] do_sve_acc+0x64/0x128 > [ 765.087272] el0_sve_acc+0x3c/0xa0 > [ 765.088356] el0t_64_sync_handler+0x114/0x130 > [ 765.089524] el0t_64_sync+0x190/0x198 So something managed to get flagged as having SVE state without having the backing storage allocated. We *were* preempted in the SVE access handler which does the allocation but I can't see the path that would trigger that since we allocate the state before setting TIF_SVE. It's possible the compiler did something funky, a decode of the backtrace might help show that?
Attachment:
signature.asc
Description: PGP signature
