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    Subject[PATCH v3 01/21] KVM: arm64: Add hyp_spin_is_locked() for basic locking assertions at EL2
    From
    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
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