Commit 8e049e0d authored by Quentin Perret's avatar Quentin Perret Committed by Marc Zyngier
Browse files

KVM: arm64: Introduce hyp_assert_lock_held() 



Introduce a poor man's lockdep implementation at EL2 which allows to
BUG() whenever a hyp spinlock is not held when it should. Hide this
feature behind a new Kconfig option that targets the EL2 object
specifically, instead of piggy backing on the existing CONFIG_LOCKDEP.
EL2 cannot WARN() cleanly to report locking issues, hence BUG() is the
only option and it is not clear whether we want this widely enabled.
This is most likely going to be useful for local testing until the EL2
WARN() situation has improved.

Signed-off-by: default avatarQuentin Perret <qperret@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210809152448.1810400-3-qperret@google.com
parent d21292f1

arch/arm64/kvm/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -46,6 +46,15 @@ if KVM 


source "virt/kvm/Kconfig"



config NVHE_EL2_DEBUG

	bool "Debug mode for non-VHE EL2 object"

	help

	  Say Y here to enable the debug mode for the non-VHE KVM EL2 object.

	  Failure reports will BUG() in the hypervisor. This is intended for

	  local EL2 hypervisor development.



	  If unsure, say N.



endif # KVM



endif # VIRTUALIZATION

arch/arm64/kvm/hyp/include/nvhe/spinlock.h

+17 −0
Original line number Diff line number Diff line
@@ -97,4 +97,21 @@ static inline bool hyp_spin_is_locked(hyp_spinlock_t *lock) 
	return lockval.owner != lockval.next;

}



#ifdef CONFIG_NVHE_EL2_DEBUG

static inline void hyp_assert_lock_held(hyp_spinlock_t *lock)

{

	/*

	 * The __pkvm_init() path accesses protected data-structures without

	 * holding locks as the other CPUs are guaranteed to not enter EL2

	 * concurrently at this point in time. The point by which EL2 is

	 * initialized on all CPUs is reflected in the pkvm static key, so

	 * wait until it is set before checking the lock state.

	 */

	if (static_branch_likely(&kvm_protected_mode_initialized))

		BUG_ON(!hyp_spin_is_locked(lock));

}

#else

static inline void hyp_assert_lock_held(hyp_spinlock_t *lock) { }

#endif



#endif /* __ARM64_KVM_NVHE_SPINLOCK_H__ */