Re: [BUG] KVM: NULL pointer dereference in kvm_tdp_mmu_map under memory pressure

punixcorn
2026-04-08T15:36:44Z

Hi Sean,

I attempted to trigger your debug patch via fault injection (zeroing
page_private on the allocated sp before it's linked), but the resulting
logs aren't meaningful -- every captured entry shows spte =
8000000000000000, a non-present SPTE, which doesn't reflect the real
crash scenario where the SPTE is present but page_private returns 0.
So I'm not sending those.

Natural reproduction is rare and I haven't caught it yet
with your patch applied.

Given that, what would you recommend as a next step? Would lockdep,
KASAN, or RCU debugging (CONFIG_PROVE_RCU) be worth enabling to catch
the violation when it happens naturally?

Environment:
- CPU: 13th Gen Intel(R) Core(TM) i5-13420H (12) @ 4.60 GHz
- RAM: 16GB (15Gi usable, 16Gi swap)
- OS: Arch Linux
- Kernel: 6.19.10-dirty #1 SMP PREEMPT_DYNAMIC Wed Apr 8 06:08:08 GMT 2026 x86_64
- /proc/cpuinfo: https://pastebin.com/pwvNYsCu
- .config: https://pastebin.com/z4fVZENs

The crash occurs while running an Android emulator (QEMU) under host
memory pressure.

Signed-off-by: punixcorn <ohyunwoods663@gmail.com>