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AJvYcCV8nRO3XKoSSn0cbML2Gqcm5rDneueSsxTbsysPh+ODsAejrDB/8GK9N3ii8caqltnhGKqgrTrw3p90nGY=@vger.kernel.org X-Gm-Message-State: AOJu0Yy6oxR4OPhQqponxBAtx299EupNCa3wOPDH61ntgvUsv0hN2u3r mFslb18zac55YviFMtUx5hB8SCWdQN9YiwHwLFTi8CVbqqrArb+Pe1P2Ceb9U/IwX7tsZp1Euhw 5++zJmA== X-Google-Smtp-Source: AGHT+IF0qsHz/W4ruaoPoUNgsNRlI9dg6Q1KxJ3doX3TWqUOAcyX6InMoydoaL0wMNT5EnILC3E6gDJbdn4= X-Received: from pljs5.prod.google.com ([2002:a17:903:3ba5:b0:269:740f:8ae8]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:da8a:b0:297:d4a5:64e5 with SMTP id d9443c01a7336-297e56be279mr1930385ad.30.1762541962031; Fri, 07 Nov 2025 10:59:22 -0800 (PST) Date: Fri, 7 Nov 2025 10:59:20 -0800 In-Reply-To: <690e0be4.a70a0220.22f260.0050.GAE@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <690e0be4.a70a0220.22f260.0050.GAE@google.com> Message-ID: Subject: Re: [syzbot] [kvm-x86?] WARNING in kvm_arch_can_dequeue_async_page_present From: Sean Christopherson To: syzbot Cc: bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, pbonzini@redhat.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, x86@kernel.org Content-Type: text/plain; charset="us-ascii" On Fri, Nov 07, 2025, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 9c0826a5d9aa Add linux-next specific files for 20251107 > git tree: linux-next > console output: https://syzkaller.appspot.com/x/log.txt?x=13a67012580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=4f8fcc6438a785e7 > dashboard link: https://syzkaller.appspot.com/bug?extid=6bea72f0c8acbde47c55 > compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14e110b4580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14ab1114580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/6b76dc0ec17f/disk-9c0826a5.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/522b6d2a1d1d/vmlinux-9c0826a5.xz > kernel image: https://storage.googleapis.com/syzbot-assets/4a58225d70f3/bzImage-9c0826a5.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+6bea72f0c8acbde47c55@syzkaller.appspotmail.com > > kvm_intel: L1TF CPU bug present and SMT on, data leak possible. See CVE-2018-3646 and https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/l1tf.html for details. > ------------[ cut here ]------------ > WARNING: arch/x86/kvm/x86.c:13965 at kvm_arch_can_dequeue_async_page_present+0x1a9/0x2f0 arch/x86/kvm/x86.c:13965, CPU#0: syz.0.17/5998 > Modules linked in: > CPU: 0 UID: 0 PID: 5998 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 > RIP: 0010:kvm_arch_can_dequeue_async_page_present+0x1a9/0x2f0 arch/x86/kvm/x86.c:13965 > Code: 00 65 48 8b 0d 58 81 72 11 48 3b 4c 24 40 75 21 48 8d 65 d8 5b 41 5c 41 5d 41 5e 41 5f 5d e9 3e af 20 0a cc e8 48 e1 79 00 90 <0f> 0b 90 b0 01 eb c0 e8 4b c1 1d 0a f3 0f 1e fa 4c 8d b3 f8 02 00 > RSP: 0018:ffffc90003167460 EFLAGS: 00010293 > RAX: ffffffff8147eee8 RBX: ffff888030280000 RCX: ffff88807fda1e80 > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000009 > RBP: ffffc900031674e8 R08: ffff88803028003f R09: 1ffff11006050007 > R10: dffffc0000000000 R11: ffffed1006050008 R12: 1ffff9200062ce8c > R13: dffffc0000000000 R14: 0000000000000000 R15: dffffc0000000000 > FS: 000055556a8c3500(0000) GS:ffff888125a79000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000000 CR3: 0000000072cc2000 CR4: 00000000003526f0 > Call Trace: > > kvm_check_async_pf_completion+0x102/0x3c0 virt/kvm/async_pf.c:158 > vcpu_enter_guest arch/x86/kvm/x86.c:11209 [inline] > vcpu_run+0x26be/0x7760 arch/x86/kvm/x86.c:11650 > kvm_arch_vcpu_ioctl_run+0x116c/0x1cb0 arch/x86/kvm/x86.c:11995 > kvm_vcpu_ioctl+0x99a/0xed0 virt/kvm/kvm_main.c:4477 > vfs_ioctl fs/ioctl.c:51 [inline] > __do_sys_ioctl fs/ioctl.c:597 [inline] > __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583 > 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: 0033:0x7f1588b8f6c9 > 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:00007ffdfcd816a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > RAX: ffffffffffffffda RBX: 00007f1588de5fa0 RCX: 00007f1588b8f6c9 > RDX: 0000000000000000 RSI: 000000000000ae80 RDI: 0000000000000006 > RBP: 00007f1588c11f91 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007f1588de5fa0 R14: 00007f1588de5fa0 R15: 0000000000000003 > /facepalm This is due to a new WARN[*] that was added to yell if KVM tries to process an async #PF after the guest disables *PV* async #PFs. But I completely forgot that KVM uses the same paths for non-PV async #PF (KVM doesn't inject anything into the guest and instead puts the vCPU into a "synthetic" HLT state so that if an IRQ/NMI comes along for the vCPU, KVM can immediately delivery the interrupt). I'll simply drop the patch. [*] https://lkml.kernel.org/r/20251015033258.50974-2-mlevitsk%40redhat.com > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > If the report is already addressed, let syzbot know by replying with: > #syz fix: exact-commit-title > > If you want syzbot to run the reproducer, reply with: > #syz test: git://repo/address.git branch-or-commit-hash > If you attach or paste a git patch, syzbot will apply it before testing. > > If you want to overwrite report's subsystems, reply with: > #syz set subsystems: new-subsystem > (See the list of subsystem names on the web dashboard) > > If the report is a duplicate of another one, reply with: > #syz dup: exact-subject-of-another-report > > If you want to undo deduplication, reply with: > #syz undup