1 files changed, 125 insertions, 0 deletions
diff --git a/arch/arm64/kvm/hyp/include/nvhe/spinlock.h b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h
new file mode 100644
index 000000000000..7c7ea8c55405
--- /dev/null
+++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h
@@ -0,0 +1,125 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * A stand-alone ticket spinlock implementation for use by the non-VHE
+ * KVM hypervisor code running at EL2.
+ *
+ * Copyright (C) 2020 Google LLC
+ * Author: Will Deacon <will@kernel.org>
+ *
+ * Heavily based on the implementation removed by c11090474d70 which was:
+ * Copyright (C) 2012 ARM Ltd.
+ */
+
+#ifndef __ARM64_KVM_NVHE_SPINLOCK_H__
+#define __ARM64_KVM_NVHE_SPINLOCK_H__
+
+#include <asm/alternative.h>
+#include <asm/lse.h>
+#include <asm/rwonce.h>
+
+typedef union hyp_spinlock {
+	u32	__val;
+	struct {
+#ifdef __AARCH64EB__
+		u16 next, owner;
+#else
+		u16 owner, next;
+#endif
+	};
+} hyp_spinlock_t;
+
+#define __HYP_SPIN_LOCK_INITIALIZER \
+	{ .__val = 0 }
+
+#define __HYP_SPIN_LOCK_UNLOCKED \
+	((hyp_spinlock_t) __HYP_SPIN_LOCK_INITIALIZER)
+
+#define DEFINE_HYP_SPINLOCK(x)	hyp_spinlock_t x = __HYP_SPIN_LOCK_UNLOCKED
+
+#define hyp_spin_lock_init(l)						\
+do {									\
+	*(l) = __HYP_SPIN_LOCK_UNLOCKED;				\
+} while (0)
+
+static inline void hyp_spin_lock(hyp_spinlock_t *lock)
+{
+	u32 tmp;
+	hyp_spinlock_t lockval, newval;
+
+	asm volatile(
+	/* Atomically increment the next ticket. */
+	ARM64_LSE_ATOMIC_INSN(
+	/* LL/SC */
+"	prfm	pstl1strm, %3\n"
+"1:	ldaxr	%w0, %3\n"
+"	add	%w1, %w0, #(1 << 16)\n"
+"	stxr	%w2, %w1, %3\n"
+"	cbnz	%w2, 1b\n",
+	/* LSE atomics */
+"	mov	%w2, #(1 << 16)\n"
+"	ldadda	%w2, %w0, %3\n"
+	__nops(3))
+
+	/* Did we get the lock? */
+"	eor	%w1, %w0, %w0, ror #16\n"
+"	cbz	%w1, 3f\n"
+	/*
+	 * No: spin on the owner. Send a local event to avoid missing an
+	 * unlock before the exclusive load.
+	 */
+"	sevl\n"
+"2:	wfe\n"
+"	ldaxrh	%w2, %4\n"
+"	eor	%w1, %w2, %w0, lsr #16\n"
+"	cbnz	%w1, 2b\n"
+	/* We got the lock. Critical section starts here. */
+"3:"
+	: "=&r" (lockval), "=&r" (newval), "=&r" (tmp), "+Q" (*lock)
+	: "Q" (lock->owner)
+	: "memory");
+}
+
+static inline void hyp_spin_unlock(hyp_spinlock_t *lock)
+{
+	u64 tmp;
+
+	asm volatile(
+	ARM64_LSE_ATOMIC_INSN(
+	/* LL/SC */
+	"	ldrh	%w1, %0\n"
+	"	add	%w1, %w1, #1\n"
+	"	stlrh	%w1, %0",
+	/* LSE atomics */
+	"	mov	%w1, #1\n"
+	"	staddlh	%w1, %0\n"
+	__nops(1))
+	: "=Q" (lock->owner), "=&r" (tmp)
+	:
+	: "memory");
+}
+
+static inline bool hyp_spin_is_locked(hyp_spinlock_t *lock)
+{
+	hyp_spinlock_t lockval = READ_ONCE(*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__ */