* [moderation/CI] Re: KVM: x86/xen: Don't drop event deliveries which race memslot updates
@ 2026-10-15 6:24 syzbot ci
2026-10-15 6:29 ` Aleksandr Nogikh
0 siblings, 1 reply; 2+ messages in thread
From: syzbot ci @ 2026-10-15 6:24 UTC (permalink / raw)
To: syzkaller-upstream-moderation; +Cc: syzbot
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:
<TASK>
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
</TASK>
***
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
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [moderation/CI] Re: KVM: x86/xen: Don't drop event deliveries which race memslot updates
2026-10-15 6:24 [moderation/CI] Re: KVM: x86/xen: Don't drop event deliveries which race memslot updates syzbot ci
@ 2026-10-15 6:29 ` Aleksandr Nogikh
0 siblings, 0 replies; 2+ messages in thread
From: Aleksandr Nogikh @ 2026-10-15 6:29 UTC (permalink / raw)
To: syzbot ci; +Cc: syzkaller-upstream-moderation, syzbot
#syz upstream
On Thu, Oct 15, 2026 at 8:24 AM syzbot ci
<syzbot+ci2fb68a675810f96c@syzkaller.appspotmail.com> wrote:
>
> 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:
> <TASK>
> 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
> </TASK>
>
>
> ***
>
> 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
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-upstream-moderation" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-upstream-moderation+unsubscribe@googlegroups.com.
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^ permalink raw reply [flat|nested] 2+ messages in thread
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2026-10-15 6:24 [moderation/CI] Re: KVM: x86/xen: Don't drop event deliveries which race memslot updates syzbot ci
2026-10-15 6:29 ` Aleksandr Nogikh
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