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Message-Id: <20201117181607.1761516-4-qperret@google.com>
Date: Tue, 17 Nov 2020 18:15:43 +0000
From: Quentin Perret <qperret@...gle.com>
To: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
James Morse <james.morse@....com>,
Julien Thierry <julien.thierry.kdev@...il.com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Rob Herring <robh+dt@...nel.org>,
Frank Rowand <frowand.list@...il.com>
Cc: "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)"
<linux-arm-kernel@...ts.infradead.org>,
open list <linux-kernel@...r.kernel.org>,
"open list:KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)"
<kvmarm@...ts.cs.columbia.edu>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE"
<devicetree@...r.kernel.org>, kernel-team@...roid.com,
android-kvm@...gle.com, Quentin Perret <qperret@...gle.com>
Subject: [RFC PATCH 03/27] KVM: arm64: Add standalone ticket spinlock
implementation for use at hyp
From: Will Deacon <will@...nel.org>
We will soon need to synchronise multiple CPUs in the hyp text at EL2.
The qspinlock-based locking used by the host is overkill for this purpose
and requires a working "percpu" implementation for the MCS nodes.
Implement a simple ticket locking scheme based heavily on the code removed
by c11090474d70 ("arm64: locking: Replace ticket lock implementation with
qspinlock").
[ qperret: removed the __KVM_NVHE_HYPERVISOR__ build-time check from
spinlock.h ]
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Quentin Perret <qperret@...gle.com>
---
arch/arm64/kvm/hyp/include/nvhe/spinlock.h | 95 ++++++++++++++++++++++
arch/arm64/kvm/hyp/include/nvhe/util.h | 25 ++++++
2 files changed, 120 insertions(+)
create mode 100644 arch/arm64/kvm/hyp/include/nvhe/spinlock.h
create mode 100644 arch/arm64/kvm/hyp/include/nvhe/util.h
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..bbfe2cbd9f62
--- /dev/null
+++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * A stand-alone ticket spinlock implementation, primarily for use by the
+ * non-VHE hypervisor code running at EL2.
+ *
+ * Copyright (C) 2020 Google LLC
+ * Author: Will Deacon <will@...nel.org>
+ *
+ * Heavily based on the implementation removed by c11090474d70 which was:
+ * Copyright (C) 2012 ARM Ltd.
+ */
+
+#ifndef __ARM64_KVM_HYP_SPINLOCK_H__
+#define __ARM64_KVM_HYP_SPINLOCK_H__
+
+#include <asm/alternative.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_init(l) \
+do { \
+ *(l) = (hyp_spinlock_t){ .__val = 0 }; \
+} 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. */
+ ALTERNATIVE(
+ /* 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 */
+" .arch_extension lse\n"
+" mov %w2, #(1 << 16)\n"
+" ldadda %w2, %w0, %3\n"
+ __nops(3),
+ ARM64_HAS_LSE_ATOMICS)
+
+ /* 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(
+ ALTERNATIVE(
+ /* LL/SC */
+ " ldrh %w1, %0\n"
+ " add %w1, %w1, #1\n"
+ " stlrh %w1, %0",
+ /* LSE atomics */
+ " .arch_extension lse\n"
+ " mov %w1, #1\n"
+ " staddlh %w1, %0\n"
+ __nops(1),
+ ARM64_HAS_LSE_ATOMICS)
+ : "=Q" (lock->owner), "=&r" (tmp)
+ :
+ : "memory");
+}
+
+#endif /* __ARM64_KVM_HYP_SPINLOCK_H__ */
diff --git a/arch/arm64/kvm/hyp/include/nvhe/util.h b/arch/arm64/kvm/hyp/include/nvhe/util.h
new file mode 100644
index 000000000000..9c58cc436a83
--- /dev/null
+++ b/arch/arm64/kvm/hyp/include/nvhe/util.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Standalone re-implementations of kernel interfaces for use at EL2.
+ * Copyright (C) 2020 Google LLC
+ * Author: Will Deacon <will@...nel.org>
+ */
+
+#ifndef __KVM_NVHE_HYPERVISOR__
+#error "Attempt to include nVHE code outside of EL2 object"
+#endif
+
+#ifndef __ARM64_KVM_NVHE_UTIL_H__
+#define __ARM64_KVM_NVHE_UTIL_H__
+
+/* Locking (hyp_spinlock_t) */
+#include <nvhe/spinlock.h>
+
+#undef spin_lock_init
+#define spin_lock_init hyp_spin_lock_init
+#undef spin_lock
+#define spin_lock hyp_spin_lock
+#undef spin_unlock
+#define spin_unlock hyp_spin_unlock
+
+#endif /* __ARM64_KVM_NVHE_UTIL_H__ */
--
2.29.2.299.gdc1121823c-goog
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