With this boot step:

SERENITY_RAM_SIZE=1G SERENITY_CPUS=4 ./Meta/serenity.sh run x86_64 Clang smp=on

We intermittently panic on shutdown with locks being held by the wrong Processor.

This was reproduced without KVM, on TCG (from my M2 MacBook).

11.946 [#2 Power State Switch Task(48:48)]: Killing remaining processes...
11.950 [#2 Finalizer Task(8:8)]: Init process quitting for shutdown.
12.331 [#1 Power State Switch Task(48:48)]: Locking all file systems...
12.331 [#1 Power State Switch Task(48:48)]: Unmounting all file systems...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 6 for the last time...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 6...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 5 for the last time...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 5...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 4 for the last time...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 4...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 3 for the last time...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 3...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 2 for the last time...
12.335 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 2...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [#1 Power State Switch Task(48:48)]: VirtualFileSystem: Unmounting file system 1...
12.339 [Power State Switch Task(48:48)]: Ext2FS: Clean unmount, setting superblock to valid state
[Power State Switch Task(48:48)]: ASSERTION FAILED: m_lock.load(AK::memory_order_relaxed) == FlatPtr(&Processor::current())
[Power State Switch Task(48:48)]: Kernel/Locking/Spinlock.h:92 in void Kernel::RecursiveSpinlock<Kernel::LockRank::FileSystem>::unlock(InterruptsState) [Rank = Kernel::LockRank::FileSystem]
[Power State Switch Task(48:48)]: KERNEL PANIC! :^(
[Power State Switch Task(48:48)]: Aborted
[Power State Switch Task(48:48)]: at Kernel/Arch/x86_64/CPU.cpp:35 in void abort()
[Power State Switch Task(48:48)]: Kernel + 0x0000000000509c30  Kernel::__panic(char const*, unsigned int, char const*) +0xf0
[Power State Switch Task(48:48)]: Kernel + 0x00000000007dcb59  abort +0x109
[Power State Switch Task(48:48)]: Kernel + 0x00000000007dca44  __assertion_failed(char const*, char const*, unsigned int, char const*) +0xa4
[Power State Switch Task(48:48)]: Kernel + 0x000000000032449e  Kernel::RecursiveSpinlock<(Kernel::LockRank)4>::unlock(Kernel::InterruptsState) +0x25e
[Power State Switch Task(48:48)]: Kernel + 0x0000000000323adb  Kernel::FileSystem::prepare_to_unmount(Kernel::Inode&) +0x24b
[Power State Switch Task(48:48)]: Kernel + 0x000000000042b913  Kernel::VirtualFileSystem::unmount(Kernel::Inode&, AK::StringView) +0x5e3
[Power State Switch Task(48:48)]: Kernel + 0x00000000007296e1  Kernel::PowerStateSwitchTask::perform_shutdown(Kernel::PowerStateSwitchTask::DoReboot) +0xf81
[Power State Switch Task(48:48)]: Kernel + 0x000000000072852b  Kernel::PowerStateSwitchTask::power_state_switch_task(void*) +0x8b