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Wed, 08 Apr 2026 08:36:42 -0700 (PDT) From: punixcorn To: seanjc@google.com, pbonzini@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, punixcorn Subject: Re: [BUG] KVM: NULL pointer dereference in kvm_tdp_mmu_map under memory pressure Date: Wed, 8 Apr 2026 15:36:50 +0000 Message-ID: <20260408153650.34484-1-ohyunwoods663@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <202604081418.sean.christopherson@intel.com> References: <202604081418.sean.christopherson@intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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