KVM: arm64: Add hyp_spin_is_locked() for basic locking assertions at EL2

Introduce hyp_spin_is_locked() so that functions can easily assert that
a given lock is held (albeit possibly by another CPU!) without having to
drag full lockdep support up to EL2.

Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210809152448.1810400-2-qperret@google.com

diff --git a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h
index 76b537f..04f65b6 100644 (file)
--- a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h
@@ -15,6 +15,7 @@
 
 #include <asm/alternative.h>
 #include <asm/lse.h>
+#include <asm/rwonce.h>
 
 typedef union hyp_spinlock {
        u32     __val;
@@ -89,4 +90,11 @@ static inline void hyp_spin_unlock(hyp_spinlock_t *lock)
        : "memory");
 }
 
+static inline bool hyp_spin_is_locked(hyp_spinlock_t *lock)
+{
+       hyp_spinlock_t lockval = READ_ONCE(*lock);
+
+       return lockval.owner != lockval.next;
+}
+
 #endif /* __ARM64_KVM_NVHE_SPINLOCK_H__ */