[syzbot ci] Re: KVM: x86/hyperv: Fix racy usage of vcpu->arch.hyperv

[syzbot ci <syzbot+ci6c27aad5db86e5b9@syzkaller.appspotmail.com>]

syzbot ci has tested the following series

[v3] KVM: x86/hyperv: Fix racy usage of vcpu->arch.hyperv
https://lore.kernel.org/all/20260625223623.3376478-1-seanjc@google.com
* [PATCH v3 01/10] KVM: x86/hyperv: Get target FIFO in hv_tlb_flush_enqueue(), not caller
* [PATCH v3 02/10] KVM: x86/hyperv: Check for NULL vCPU Hyper-V object in kvm_hv_get_tlb_flush_fifo()
* [PATCH v3 03/10] KVM: x86/hyperv: Ensure vCPU's Hyper-V object is initialized on cross-vCPU accesses
* [PATCH v3 04/10] KVM: x86/xen: Punt singleshot timer hcalls to userspace if Xen vCPU ID isn't set
* [PATCH v3 05/10] KVM: x86/xen: Consolidate checks on Xen vCPU ID for singleshot timer hypercalls
* [PATCH v3 06/10] KVM: Initialize a vCPU's index to '-1' while it's being created
* [PATCH v3 07/10] KVM: Move nVMX's lockdep logic for vcpu->mutex to a common helper
* [PATCH v3 08/10] KVM: x86: Treat a vCPU as unreachable if its index is invalid
* [PATCH v3 09/10] KVM: x86/hyperv: Assert vCPU's mutex is held in to_hv_vcpu()
* [PATCH v3 10/10] KVM: x86/hyperv: Use {READ,WRITE}_ONCE for cross-task synic->active accesses

and found the following issue:
WARNING in kvm_hv_vcpu_uninit

Full report is available here:
https://ci.syzbot.org/series/6864cbe8-ce00-47d1-b4b1-abc7d1528d4e

***

WARNING in kvm_hv_vcpu_uninit

tree:      kvm-next
URL:       https://kernel.googlesource.com/pub/scm/virt/kvm/kvm/
base:      a204badd8432f93b7e862e7dac6db0fe3d65f370
arch:      amd64
compiler:  Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
config:    https://ci.syzbot.org/builds/0627391d-c4d6-4820-99f0-31a8b51ba783/config
syz repro: https://ci.syzbot.org/findings/cdadfdf2-8445-4193-a3a6-bf878176b493/syz_repro

------------[ cut here ]------------
debug_locks && !(lock_is_held(&(&vcpu->mutex)->dep_map) || vcpu->vcpu_idx < 0 || !refcount_read(&vcpu->kvm->users_count))
WARNING: ./include/linux/kvm_host.h:996 at kvm_lockdep_assert_vcpu_is_locked_or_unreachable include/linux/kvm_host.h:994 [inline], CPU#1: syz.1.34/5967
WARNING: ./include/linux/kvm_host.h:996 at to_hv_vcpu arch/x86/kvm/hyperv.h:79 [inline], CPU#1: syz.1.34/5967
WARNING: ./include/linux/kvm_host.h:996 at kvm_hv_vcpu_uninit+0x198/0x210 arch/x86/kvm/hyperv.c:906, CPU#1: syz.1.34/5967
Modules linked in:
CPU: 1 UID: 0 PID: 5967 Comm: syz.1.34 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
RIP: 0010:kvm_lockdep_assert_vcpu_is_locked_or_unreachable include/linux/kvm_host.h:994 [inline]
RIP: 0010:to_hv_vcpu arch/x86/kvm/hyperv.h:79 [inline]
RIP: 0010:kvm_hv_vcpu_uninit+0x198/0x210 arch/x86/kvm/hyperv.c:906
Code: 48 89 df e8 0a 55 d8 00 48 c7 03 00 00 00 00 eb 05 e8 5c 16 6d 00 5b 41 5c 41 5e 41 5f 5d e9 ff 16 4d 0a cc e8 49 16 6d 00 90 <0f> 0b 90 e9 65 ff ff ff 48 c7 c1 e0 bb 2f 90 80 e1 07 80 c1 03 38
RSP: 0018:ffffc9000390f960 EFLAGS: 00010293
RAX: ffffffff8158e9e7 RBX: ffff8881bc192880 RCX: ffff88816ac70000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffff888101fa1743 R09: 1ffff110203f42e8
R10: dffffc0000000000 R11: ffffed10203f42e9 R12: 0000000000000000
R13: 00000000fffffff8 R14: ffff888101fa1740 R15: dffffc0000000000
FS:  00007f47c1e886c0(0000) GS:ffff8882a92b6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000c64000 CR3: 000000016a5e7000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 kvm_arch_vcpu_destroy+0x1a9/0x380 arch/x86/kvm/x86.c:9413
 kvm_vm_ioctl_create_vcpu+0x615/0x990 virt/kvm/kvm_main.c:4269
 kvm_vm_ioctl+0x886/0xd30 virt/kvm/kvm_main.c:5168
 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+0x174/0x580 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f47c0f9caeb
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007f47c1e87ee0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f47c1215fa0 RCX: 00007f47c0f9caeb
RDX: 0000000000000000 RSI: 000000000000ae41 RDI: 00000000000000f7
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000200000c00000 R11: 0000000000000246 R12: 0000200000c00000
R13: 0000000000000153 R14: 0000200000000400 R15: 00007ffe526558c8
 </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

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