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Mon, 13 Oct 2025 14:23:57 -0700 (PDT) Date: Mon, 13 Oct 2025 14:23:57 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <68ed6ded.050a0220.91a22.01eb.GAE@google.com> Subject: [moderation/CI] Re: KVM: x86: Unify L1TF flushing under per-CPU variable From: syzbot ci To: syzkaller-upstream-moderation@googlegroups.com Cc: syzbot@lists.linux.dev Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v1] KVM: x86: Unify L1TF flushing under per-CPU variable https://lore.kernel.org/all/20251013-b4-l1tf-percpu-v1-1-d65c5366ea1a@google.com * [PATCH] KVM: x86: Unify L1TF flushing under per-CPU variable and found the following issue: BUG: using __this_cpu_write() in preemptible code in x86_emulate_instruction Full report is available here: https://ci.syzbot.org/series/c0a39c51-4121-4883-a21f-4277f63b3118 *** BUG: using __this_cpu_write() in preemptible code in x86_emulate_instruction tree: kvm-next URL: https://kernel.googlesource.com/pub/scm/virt/kvm/kvm/ base: 6b36119b94d0b2bb8cea9d512017efafd461d6ac arch: amd64 compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 config: https://ci.syzbot.org/builds/a964957a-128c-43dd-b6df-7758575a9993/config C repro: https://ci.syzbot.org/findings/c0c645e8-abe2-437f-aa29-1adf339cb732/c_repro syz repro: https://ci.syzbot.org/findings/c0c645e8-abe2-437f-aa29-1adf339cb732/syz_repro BUG: using __this_cpu_write() in preemptible [00000000] code: syz.0.17/5962 caller is kvm_set_cpu_l1tf_flush_l1d arch/x86/include/asm/kvm_host.h:2486 [inline] caller is x86_emulate_instruction+0x1a4/0x1f70 arch/x86/kvm/x86.c:9405 CPU: 1 UID: 0 PID: 5962 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 check_preemption_disabled+0x10a/0x120 lib/smp_processor_id.c:47 kvm_set_cpu_l1tf_flush_l1d arch/x86/include/asm/kvm_host.h:2486 [inline] x86_emulate_instruction+0x1a4/0x1f70 arch/x86/kvm/x86.c:9405 kvm_mmu_page_fault+0x91a/0xb70 arch/x86/kvm/mmu/mmu.c:6385 __vmx_handle_exit arch/x86/kvm/vmx/vmx.c:6624 [inline] vmx_handle_exit+0x10a4/0x18c0 arch/x86/kvm/vmx/vmx.c:6641 vcpu_enter_guest arch/x86/kvm/x86.c:11461 [inline] vcpu_run+0x4359/0x6fc0 arch/x86/kvm/x86.c:11619 kvm_arch_vcpu_ioctl_run+0xfc9/0x1940 arch/x86/kvm/x86.c:11958 kvm_vcpu_ioctl+0x95c/0xe90 virt/kvm/kvm_main.c:4476 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:584 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f0f9698eec9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fff7c8600c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f0f96be5fa0 RCX: 00007f0f9698eec9 RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000005 RBP: 00007f0f96a11f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f0f96be5fa0 R14: 00007f0f96be5fa0 R15: 0000000000000003 *** If these findings have caused you to resend the series or submit a separate fix, please add the following tag to your commit message: Tested-by: syzbot@syzkaller.appspotmail.com --- This report is generated by a bot. It may contain errors. syzbot ci engineers can be reached at syzkaller@googlegroups.com. The email will later be sent to: [bp@alien8.de dave.hansen@linux.intel.com hpa@zytor.com jackmanb@google.com kvm@vger.kernel.org linux-kernel@vger.kernel.org mingo@redhat.com pbonzini@redhat.com seanjc@google.com tglx@linutronix.de x86@kernel.org] If the report looks fine to you, reply with: #syz upstream