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Date:   Thu, 29 Jul 2021 14:27:58 +0100
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Subject: [PATCH v3 01/21] KVM: arm64: Add hyp_spin_is_locked() for basic
 locking assertions at EL2
From:   Quentin Perret <qperret@google.com>
To:     maz@kernel.org, james.morse@arm.com, alexandru.elisei@arm.com,
        suzuki.poulose@arm.com, catalin.marinas@arm.com, will@kernel.org
Cc:     linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        linux-kernel@vger.kernel.org, ardb@kernel.org, qwandor@google.com,
        tabba@google.com, dbrazdil@google.com, kernel-team@android.com,
        Quentin Perret <qperret@google.com>
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From: Will Deacon <will@kernel.org>

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>
---
 arch/arm64/kvm/hyp/include/nvhe/spinlock.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h
index 76b537f8d1c6..04f65b655fcf 100644
--- 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__ */
-- 
2.32.0.432.gabb21c7263-goog