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Wed, 14 Oct 2026 23:24:16 -0700 (PDT) Date: Wed, 14 Oct 2026 23:24:16 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6ad07190.7ce658ee.3494bd.0006.GAE@google.com> Subject: [moderation/CI] Re: KVM: x86/xen: Don't drop event deliveries which race memslot updates 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 [v2] KVM: x86/xen: Don't drop event deliveries which race memslot updates https://lore.kernel.org/all/20261014220508.518772-1-dwmw2@infradead.org * [PATCH v2 01/11] KVM: pfncache: Return -EAGAIN for a lookup which hits an invalid memslot * [PATCH v2 02/11] KVM: pfncache: Add a 'wait' argument to the refresh and activate functions * [PATCH v2 03/11] KVM: x86/xen: Don't block on xen_lock within the vCPU's kvm->srcu section * [PATCH v2 04/11] KVM: x86/xen: Wait out memslot updates in the Xen attribute ioctls * [PATCH v2 05/11] KVM: x86/xen: Don't lose the timer event when delivery fails transiently * [PATCH v2 06/11] KVM: x86/xen: Retry event channel delivery which races a memslot update * [PATCH v2 07/11] KVM: x86/xen: Extract delivery of event to vCPU into a separate helper * [PATCH v2 08/11] KVM: x86/xen: Explicitly tag "shared info" page as never being dirty tracked * [PATCH v2 09/11] KVM: x86/xen: Don't dirty track "vCPU info" page * [PATCH v2 10/11] KVM: x86: Request the guest TLB flush from record_steal_time() * [PATCH v2 11/11] KVM: selftests: Add Xen evtchn vs memslot-update race test and found the following issue: WARNING: suspicious RCU usage in kvm_gpc_check Full report is available here: https://ci.syzbot.org/series/cde10220-9f8c-48fe-a62d-36d3df4d9a0b *** WARNING: suspicious RCU usage in kvm_gpc_check tree: kvm-next URL: https://kernel.googlesource.com/pub/scm/virt/kvm/kvm/ base: d4b7fb647204f0c81dfeae2d1a708e4d858e0c94 arch: amd64 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 config: https://ci.syzbot.org/builds/dbdeec8a-a092-44d6-96b1-12ae99a6a0ce/config AI triage: https://ci.syzbot.org/findings/35b5a98d-93a1-4f38-ad62-620c40c551e8/triage_trajectory ============================= WARNING: suspicious RCU usage syzkaller #0 Not tainted ----------------------------- ./include/linux/kvm_host.h:1094 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 locks held by syz.0.18064/14640: 3, last CPU#0: #0: ffff8881133851a8 (&vcpu->mutex){+.+.}-{4:4}, at: kvm_vcpu_ioctl+0x27f/0xfd0 #1: ffff8880201d5d30 (&kvm->arch.xen.xen_lock){+.+.}-{4:4}, at: kvm_xen_vcpu_set_attr+0x4d/0x1250 #2: ffff8881133861e0 (&gpc->lock){....}-{3:3}, at: xen_get_guest_pvclock+0x29/0x260 stack backtrace: CPU: 0 UID: 0 PID: 14640 Comm: syz.0.18064 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+0xe8/0x150 lockdep_rcu_suspicious+0x140/0x1d0 kvm_gpc_check+0x325/0x380 xen_get_guest_pvclock+0x3e/0x260 kvm_xen_start_timer+0x160/0x5f0 kvm_xen_vcpu_set_attr+0xbb2/0x1250 kvm_arch_vcpu_ioctl+0x1485/0x23a0 kvm_vcpu_ioctl+0x7e3/0xfd0 __se_sys_ioctl+0xfc/0x170 do_syscall_64+0x166/0x520 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3c49f9e559 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f3c4ae4a028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00007f3c4a226090 RCX: 00007f3c49f9e559 RDX: 00002000000000c0 RSI: 000000004048aecb RDI: 000000000000000a RBP: 00007f3c4a0358b0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f3c4a226128 R14: 00007f3c4a226090 R15: 00007ffed7dff5b8 *** 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. To test a fix for this bug, please reply with `#syz test` (on a separate line) and attach the patch to the email. Notes: - The patch will be applied on top of the tested series (as an incremental fix). - To test a new version of the whole series, please send it directly to syzbot@lists.linux.dev. - Arguments like custom git repos and branches are not supported. The email will later be sent to: [dwmw2@infradead.org dwmw@amazon.co.uk fgriffo@amazon.co.uk kvm@vger.kernel.org linux-kernel@vger.kernel.org linux-kselftest@vger.kernel.org paul@xen.org pbonzini@redhat.com seanjc@google.com vkuznets@redhat.com] If the report looks fine to you, reply with: #syz upstream If the report is a false positive, reply with #syz invalid