On Tue, 17 Oct 2023 at 17:52, Mark Brown <broonie@xxxxxxxxxx> wrote: > > 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? This is only seen on 6.5.8-rc2 and seen only once. I have checked on mainline / next and other stable branches and this crash is not seen anywhere else. However, I will keep checking them on other branches and next and mainline. > > > [ 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? We have not uploaded vmlinux and System.map to this specific build. However, I have requested to have these files get uploaded for upcoming builds. - Naresh
