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
Subject: [PATCH v1 25/44] KVM: arm64: Introduce hyp_rwlock_t
Date: Wed, 27 Mar 2024 17:35:12 +0000 [thread overview]
Message-ID: <20240327173531.1379685-26-tabba@google.com> (raw)
In-Reply-To: <20240327173531.1379685-1-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__ */
--
2.44.0.478.gd926399ef9-goog
next prev parent reply other threads:[~2024-03-27 17:36 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-27 17:34 [PATCH v1 00/44] KVM: arm64: Preamble for pKVM Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 01/44] KVM: arm64: Change kvm_handle_mmio_return() return polarity Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 02/44] KVM: arm64: Use enum instead of helper for checking FP-state Fuad Tabba
2024-03-28 16:19 ` Mark Brown
2024-04-08 7:39 ` Marc Zyngier
2024-04-08 13:39 ` Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 03/44] KVM: arm64: Move setting the page as dirty out of the critical section Fuad Tabba
2024-04-08 7:41 ` Marc Zyngier
2024-04-08 15:41 ` Fuad Tabba
2024-04-08 15:53 ` Marc Zyngier
2024-04-08 15:57 ` Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 04/44] KVM: arm64: Avoid BUG-ing from the host abort path Fuad Tabba
2024-04-08 7:44 ` Marc Zyngier
2024-04-08 13:48 ` Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 05/44] KVM: arm64: Check for PTE validity when checking for executable/cacheable Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 06/44] KVM: arm64: Avoid BBM when changing only s/w bits in Stage-2 PTE Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 07/44] KVM: arm64: Support TLB invalidation in guest context Fuad Tabba
2024-04-15 11:36 ` Marc Zyngier
2024-04-15 15:02 ` Fuad Tabba
2024-04-15 15:59 ` Marc Zyngier
2024-03-27 17:34 ` [PATCH v1 08/44] KVM: arm64: Simplify vgic-v3 hypercalls Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 09/44] KVM: arm64: Add is_pkvm_initialized() helper Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 10/44] KVM: arm64: Introduce predicates to check for protected state Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 11/44] KVM: arm64: Split up nvhe/fixed_config.h Fuad Tabba
2024-03-27 17:34 ` [PATCH v1 12/44] KVM: arm64: Move pstate reset value definitions to kvm_arm.h Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 13/44] KVM: arm64: Clarify rationale for ZCR_EL1 value restored on guest exit Fuad Tabba
2024-03-28 18:53 ` Mark Brown
2024-04-08 13:34 ` Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 14/44] KVM: arm64: Refactor calculating SVE state size to use helpers Fuad Tabba
2024-03-28 18:57 ` Mark Brown
2024-04-08 13:35 ` Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 15/44] KVM: arm64: Use active guest SVE vector length on guest restore Fuad Tabba
2024-03-28 19:17 ` Mark Brown
2024-04-09 9:34 ` Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 16/44] KVM: arm64: Do not map the host fpsimd state to hyp in pKVM Fuad Tabba
2024-03-28 19:20 ` Mark Brown
2024-03-27 17:35 ` [PATCH v1 17/44] KVM: arm64: Move some kvm_psci functions to a shared header Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 18/44] KVM: arm64: Refactor reset_mpidr() to extract its computation Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 19/44] KVM: arm64: Refactor kvm_vcpu_enable_ptrauth() for hyp use Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 20/44] KVM: arm64: Refactor enter_exception64() Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 21/44] KVM: arm64: Add PC_UPDATE_REQ flags covering all PC updates Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 22/44] KVM: arm64: Add vcpu flag copy primitive Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 23/44] KVM: arm64: Introduce gfn_to_memslot_prot() Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 24/44] KVM: arm64: Do not use the hva in kvm_handle_guest_abort() Fuad Tabba
2024-03-27 17:35 ` Fuad Tabba [this message]
2024-03-27 17:35 ` [PATCH v1 26/44] KVM: arm64: Add atomics-based checking refcount implementation at EL2 Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 27/44] KVM: arm64: Use atomic refcount helpers for 'struct hyp_page::refcount' Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 28/44] KVM: arm64: Remove locking from EL2 allocation fast-paths Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 29/44] KVM: arm64: Reformat/beautify PTP hypercall documentation Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 30/44] KVM: arm64: Rename firmware pseudo-register documentation file Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 31/44] KVM: arm64: Document the KVM/arm64-specific calls in hypercalls.rst Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 32/44] KVM: arm64: Prevent kmemleak from accessing .hyp.data Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 33/44] KVM: arm64: Issue CMOs when tearing down guest s2 pages Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 34/44] KVM: arm64: Do not set the virtual timer offset for protected vCPUs Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 35/44] KVM: arm64: Fix comment for __pkvm_vcpu_init_traps() Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 36/44] KVM: arm64: Do not re-initialize the KVM lock Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 37/44] KVM: arm64: Check directly whether a vcpu is protected Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 38/44] KVM: arm64: Trap debug break and watch from guest Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 39/44] KVM: arm64: Restrict protected VM capabilities Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 40/44] KVM: arm64: Do not support MTE for protected VMs Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 41/44] KVM: arm64: Move pkvm_vcpu_init_traps() to hyp vcpu init Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 42/44] KVM: arm64: Fix initializing traps in protected mode Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 43/44] KVM: arm64: Advertise GICv3 sysreg interface to protected guests Fuad Tabba
2024-03-27 17:35 ` [PATCH v1 44/44] KVM: arm64: Force injection of a data abort on NISV MMIO exit Fuad Tabba
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20240327173531.1379685-26-tabba@google.com \
--to=tabba@google.com \
--cc=alexandru.elisei@arm.com \
--cc=broonie@kernel.org \
--cc=catalin.marinas@arm.com \
--cc=james.morse@arm.com \
--cc=joey.gouly@arm.com \
--cc=kvmarm@lists.linux.dev \
--cc=mark.rutland@arm.com \
--cc=maz@kernel.org \
--cc=oliver.upton@linux.dev \
--cc=philmd@linaro.org \
--cc=qperret@google.com \
--cc=rananta@google.com \
--cc=seanjc@google.com \
--cc=suzuki.poulose@arm.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.