From: Fuad Tabba <tabba@google.com>
To: kvmarm@lists.linux.dev
Cc: maz@kernel.org, will@kernel.org, qperret@google.com,
tabba@google.com, seanjc@google.com, alexandru.elisei@arm.com,
catalin.marinas@arm.com, philmd@linaro.org, james.morse@arm.com,
suzuki.poulose@arm.com, oliver.upton@linux.dev,
mark.rutland@arm.com, broonie@kernel.org, joey.gouly@arm.com,
rananta@google.com, smostafa@google.com
Subject: [PATCH v3 25/31] KVM: arm64: Introduce hyp_rwlock_t
Date: Fri, 19 Apr 2024 08:59:35 +0100 [thread overview]
Message-ID: <20240419075941.4085061-26-tabba@google.com> (raw)
In-Reply-To: <20240419075941.4085061-1-tabba@google.com>
From: Will Deacon <will@kernel.org>
Introduce a simple counter-based rwlock for EL2 which can reduce locking
contention on read-mostly data structures when compared to a spinlock.
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Fuad Tabba <tabba@google.com>
---
arch/arm64/kvm/hyp/include/nvhe/rwlock.h | 129 +++++++++++++++++++++++
1 file changed, 129 insertions(+)
create mode 100644 arch/arm64/kvm/hyp/include/nvhe/rwlock.h
diff --git a/arch/arm64/kvm/hyp/include/nvhe/rwlock.h b/arch/arm64/kvm/hyp/include/nvhe/rwlock.h
new file mode 100644
index 000000000000..365084497e59
--- /dev/null
+++ b/arch/arm64/kvm/hyp/include/nvhe/rwlock.h
@@ -0,0 +1,129 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * A stand-alone rwlock implementation for use by the non-VHE KVM
+ * hypervisor code running at EL2. This is *not* a fair lock and is
+ * likely to scale very badly under contention.
+ *
+ * Copyright (C) 2022 Google LLC
+ * Author: Will Deacon <will@kernel.org>
+ *
+ * Heavily based on the implementation removed by 087133ac9076 which was:
+ * Copyright (C) 2012 ARM Ltd.
+ */
+
+#ifndef __ARM64_KVM_NVHE_RWLOCK_H__
+#define __ARM64_KVM_NVHE_RWLOCK_H__
+
+#include <linux/bits.h>
+
+typedef struct {
+ u32 __val;
+} hyp_rwlock_t;
+
+#define __HYP_RWLOCK_INITIALIZER \
+ { .__val = 0 }
+
+#define __HYP_RWLOCK_UNLOCKED \
+ ((hyp_rwlock_t) __HYP_RWLOCK_INITIALIZER)
+
+#define DEFINE_HYP_RWLOCK(x) hyp_rwlock_t x = __HYP_RWLOCK_UNLOCKED
+
+#define hyp_rwlock_init(l) \
+do { \
+ *(l) = __HYP_RWLOCK_UNLOCKED; \
+} while (0)
+
+#define __HYP_RWLOCK_WRITER_BIT 31
+
+static inline void hyp_write_lock(hyp_rwlock_t *lock)
+{
+ u32 tmp;
+
+ asm volatile(ARM64_LSE_ATOMIC_INSN(
+ /* LL/SC */
+ " sevl\n"
+ "1: wfe\n"
+ "2: ldaxr %w0, %1\n"
+ " cbnz %w0, 1b\n"
+ " stxr %w0, %w2, %1\n"
+ " cbnz %w0, 2b\n"
+ __nops(1),
+ /* LSE atomics */
+ "1: mov %w0, wzr\n"
+ "2: casa %w0, %w2, %1\n"
+ " cbz %w0, 3f\n"
+ " ldxr %w0, %1\n"
+ " cbz %w0, 2b\n"
+ " wfe\n"
+ " b 1b\n"
+ "3:")
+ : "=&r" (tmp), "+Q" (lock->__val)
+ : "r" (BIT(__HYP_RWLOCK_WRITER_BIT))
+ : "memory");
+}
+
+static inline void hyp_write_unlock(hyp_rwlock_t *lock)
+{
+ asm volatile(ARM64_LSE_ATOMIC_INSN(
+ " stlr wzr, %0",
+ " swpl wzr, wzr, %0")
+ : "=Q" (lock->__val) :: "memory");
+}
+
+static inline void hyp_read_lock(hyp_rwlock_t *lock)
+{
+ u32 tmp, tmp2;
+
+ asm volatile(
+ " sevl\n"
+ ARM64_LSE_ATOMIC_INSN(
+ /* LL/SC */
+ "1: wfe\n"
+ "2: ldaxr %w0, %2\n"
+ " add %w0, %w0, #1\n"
+ " tbnz %w0, %3, 1b\n"
+ " stxr %w1, %w0, %2\n"
+ " cbnz %w1, 2b\n"
+ __nops(1),
+ /* LSE atomics */
+ "1: wfe\n"
+ "2: ldxr %w0, %2\n"
+ " adds %w1, %w0, #1\n"
+ " tbnz %w1, %3, 1b\n"
+ " casa %w0, %w1, %2\n"
+ " sbc %w0, %w1, %w0\n"
+ " cbnz %w0, 2b")
+ : "=&r" (tmp), "=&r" (tmp2), "+Q" (lock->__val)
+ : "i" (__HYP_RWLOCK_WRITER_BIT)
+ : "cc", "memory");
+}
+
+static inline void hyp_read_unlock(hyp_rwlock_t *lock)
+{
+ u32 tmp, tmp2;
+
+ asm volatile(ARM64_LSE_ATOMIC_INSN(
+ /* LL/SC */
+ "1: ldxr %w0, %2\n"
+ " sub %w0, %w0, #1\n"
+ " stlxr %w1, %w0, %2\n"
+ " cbnz %w1, 1b",
+ /* LSE atomics */
+ " movn %w0, #0\n"
+ " staddl %w0, %2\n"
+ __nops(2))
+ : "=&r" (tmp), "=&r" (tmp2), "+Q" (lock->__val)
+ :
+ : "memory");
+}
+
+#ifdef CONFIG_NVHE_EL2_DEBUG
+static inline void hyp_assert_write_lock_held(hyp_rwlock_t *lock)
+{
+ BUG_ON(!(READ_ONCE(lock->__val) & BIT(__HYP_RWLOCK_WRITER_BIT)));
+}
+#else
+static inline void hyp_assert_write_lock_held(hyp_rwlock_t *lock) { }
+#endif
+
+#endif /* __ARM64_KVM_NVHE_RWLOCK_H__ */
--
2.44.0.769.g3c40516874-goog
next prev parent reply other threads:[~2024-04-19 8:00 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-19 7:59 [PATCH v3 00/31] KVM: arm64: Preamble for pKVM Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 01/31] KVM: arm64: Initialize the kvm host data's fpsimd_state pointer in pKVM Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 02/31] KVM: arm64: Move guest_owns_fp_regs() to increase its scope Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 03/31] KVM: arm64: Refactor checks for FP state ownership Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 04/31] KVM: arm64: Do not re-initialize the KVM lock Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 05/31] KVM: arm64: Issue CMOs when tearing down guest s2 pages Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 06/31] KVM: arm64: Avoid BUG-ing from the host abort path Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 07/31] KVM: arm64: Check for PTE validity when checking for executable/cacheable Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 08/31] KVM: arm64: Avoid BBM when changing only s/w bits in Stage-2 PTE Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 09/31] KVM: arm64: Support TLB invalidation in guest context Fuad Tabba
2024-04-19 20:54 ` Oliver Upton
2024-04-22 8:11 ` Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 10/31] KVM: arm64: Do not map the host fpsimd state to hyp in pKVM Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 11/31] KVM: arm64: Remove locking from EL2 allocation fast-paths Fuad Tabba
2024-04-19 20:42 ` Oliver Upton
2024-04-22 8:09 ` Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 12/31] KVM: arm64: Prevent kmemleak from accessing .hyp.data Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 13/31] KVM: arm64: Fix comment for __pkvm_vcpu_init_traps() Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 14/31] KVM: arm64: Change kvm_handle_mmio_return() return polarity Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 15/31] KVM: arm64: Move setting the page as dirty out of the critical section Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 16/31] KVM: arm64: Simplify vgic-v3 hypercalls Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 17/31] KVM: arm64: Add is_pkvm_initialized() helper Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 18/31] KVM: arm64: Introduce and use predicates that check for protected VMs Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 19/31] KVM: arm64: Move pstate reset value definitions to kvm_arm.h Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 20/31] KVM: arm64: Clarify rationale for ZCR_EL1 value restored on guest exit Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 21/31] KVM: arm64: Refactor calculating SVE state size to use helpers Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 22/31] KVM: arm64: Move some kvm_psci functions to a shared header Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 23/31] KVM: arm64: Refactor reset_mpidr() to extract its computation Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 24/31] KVM: arm64: Refactor kvm_vcpu_enable_ptrauth() for hyp use Fuad Tabba
2024-04-19 7:59 ` Fuad Tabba [this message]
2024-04-19 7:59 ` [PATCH v3 26/31] KVM: arm64: Add atomics-based checking refcount implementation at EL2 Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 27/31] KVM: arm64: Use atomic refcount helpers for 'struct hyp_page::refcount' Fuad Tabba
2024-04-19 20:52 ` Oliver Upton
2024-04-22 8:10 ` Fuad Tabba
2024-04-22 13:08 ` Fuad Tabba
2024-04-22 20:46 ` Oliver Upton
2024-04-22 23:44 ` Will Deacon
2024-04-23 1:15 ` Oliver Upton
2024-04-19 7:59 ` [PATCH v3 28/31] KVM: arm64: Reformat/beautify PTP hypercall documentation Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 29/31] KVM: arm64: Rename firmware pseudo-register documentation file Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 30/31] KVM: arm64: Document the KVM/arm64-specific calls in hypercalls.rst Fuad Tabba
2024-04-19 7:59 ` [PATCH v3 31/31] KVM: arm64: Force injection of a data abort on NISV MMIO exit Fuad Tabba
2024-04-19 20:28 ` Oliver Upton
2024-04-22 8:07 ` Fuad Tabba
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