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Tue, 11 Aug 2026 08:14:01 -0700 (PDT) Date: Tue, 11 Aug 2026 08:14:01 -0700 In-Reply-To: X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a7b3c39.3668565d.e8814.0001.GAE@google.com> Subject: Re: [syzbot] [kvm-x86?] [kvm?] WARNING: locking bug in kvm_xen_set_evtchn_fast From: syzbot To: linux-kernel@vger.kernel.org, nogikh@google.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: WARNING: locking bug in kvm_xen_set_evtchn_fast ============================= [ BUG: Invalid wait context ] syzkaller #0 Not tainted ----------------------------- swapper/0/0 is trying to lock: ffff8880364ed370 (&gpc->lock){....}-{3:3}, at: kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1822 other info that might help us debug this: context-{2:2} 1 lock held by swapper/0/0: #0: ffff8880364ed8d0 (&kvm->srcu){.?.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:187 [inline] #0: ffff8880364ed8d0 (&kvm->srcu){.?.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:294 [inline] #0: ffff8880364ed8d0 (&kvm->srcu){.?.+}-{0:0}, at: kvm_xen_set_evtchn_fast+0x1bc/0x9a0 arch/x86/kvm/xen.c:1820 stack backtrace: CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_lock_invalid_wait_context kernel/locking/lockdep.c:4830 [inline] check_wait_context kernel/locking/lockdep.c:4902 [inline] __lock_acquire+0xe39/0x2cf0 kernel/locking/lockdep.c:5187 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __raw_read_lock_irqsave include/linux/rwlock_api_smp.h:174 [inline] _raw_read_lock_irqsave+0x48/0x60 kernel/locking/spinlock.c:240 kvm_xen_set_evtchn_fast+0x1f4/0x9a0 arch/x86/kvm/xen.c:1822 xen_timer_callback+0x109/0x220 arch/x86/kvm/xen.c:140 __run_hrtimer kernel/time/hrtimer.c:2032 [inline] __hrtimer_run_queues+0x371/0xa10 kernel/time/hrtimer.c:2096 hrtimer_interrupt+0x448/0x910 kernel/time/hrtimer.c:2215 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1051 [inline] __sysvec_apic_timer_interrupt+0x102/0x430 arch/x86/kernel/apic/apic.c:1068 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline] sysvec_apic_timer_interrupt+0xa1/0xc0 arch/x86/kernel/apic/apic.c:1062 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64 Code: 2c 64 02 e9 83 02 03 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 23 5a 14 00 fb f4 cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 RSP: 0018:ffffffff8e207de0 EFLAGS: 00000246 RAX: 00000000000ce103 RBX: ffffffff81994630 RCX: 0000000080000001 RDX: 0000000000000001 RSI: ffffffff8dcc8ad1 RDI: ffffffff8c038b80 RBP: ffffffff8e207eb8 R08: ffff8880b86338db R09: 1ffff110170c671b R10: dffffc0000000000 R11: ffffed10170c671c R12: 0000000000000000 R13: 1ffffffff1c51dd8 R14: 1ffffffff1c40fc4 R15: dffffc0000000000 arch_safe_halt arch/x86/kernel/process.c:767 [inline] default_idle+0x9/0x20 arch/x86/kernel/process.c:768 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:199 [inline] do_idle+0x2e0/0x540 kernel/sched/idle.c:355 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454 rest_init+0x2de/0x300 init/main.c:717 start_kernel+0x392/0x3e0 init/main.c:1175 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x157 ---------------- Code disassembly (best guess): 0: 2c 64 sub $0x64,%al 2: 02 e9 add %cl,%ch 4: 83 02 03 addl $0x3,(%rdx) 7: 00 cc add %cl,%ah 9: cc int3 a: cc int3 b: 90 nop c: 90 nop d: 90 nop e: 90 nop f: 90 nop 10: 90 nop 11: 90 nop 12: 90 nop 13: 90 nop 14: 90 nop 15: 90 nop 16: 90 nop 17: 90 nop 18: 90 nop 19: 90 nop 1a: 90 nop 1b: f3 0f 1e fa endbr64 1f: 66 90 xchg %ax,%ax 21: 0f 00 2d 23 5a 14 00 verw 0x145a23(%rip) # 0x145a4b 28: fb sti 29: f4 hlt * 2a: c3 ret <-- trapping instruction 2b: cc int3 2c: cc int3 2d: cc int3 2e: cc int3 2f: cc int3 30: cc int3 31: cc int3 32: cc int3 33: cc int3 34: cc int3 35: cc int3 36: cc int3 37: cc int3 38: cc int3 39: cc int3 3a: cc int3 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: 90 nop 3f: 90 nop Tested on: commit: d58772d8 Merge tag 'regmap-fix-v7.2-rc7' of git://git... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=10851079580000 kernel config: https://syzkaller.appspot.com/x/.config?x=c9e57f4ebf5743f1 dashboard link: https://syzkaller.appspot.com/bug?extid=919877893c9d28162dc2 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 Note: no patches were applied.