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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=FdcXk5XwPP97RT6Rrd5i1sKrdPrNLW7yQE5BzOD9Aa4=; b=lS7Dq2ZF1SHVPe7V8xYRlhh1bLn+F3BYSvBHztwvW6QPKXiRGCPfiu8sMhBa996Vjj ol1y9IGSf7fMEsr8hy5uNZguGRNZMwmZOc6JjDYCWim+RQYbon9B2BYuRYCmf8nebIYi iz2PY39aYY/IS0oxia4SXLox5If+GLrDuWgX8zUdMjCRNtLyWTJr5j1APscZ3U1NuJ3x XIveunKSRjzxnVobfahV+Pf6msLt9sfzkzRBNYTa0waQMKaoL+4YI1cr498tuX0SVKL7 DAyv4fNr5cTrAkyf2sNspFKlk+jtcFuVnIJK1+DG6Fj/un8kp3YchmLaAzlx451QC3C5 p0MQ== X-Gm-Message-State: AOAM533kY10ZM/XvLL1EoljxJQ5aH/mVlqTozZKVILRuM66v2bBF6PAT 8QNX1Ub8A1ww0V8OTeKv5nGwJaoll0vW X-Google-Smtp-Source: ABdhPJyl9JkZuAxlwZjUkJm5Ml5+4k+oG9V/LVsBit2ZNyEdffzcwrN+lSVgxsKMVJ/hAc3WVfndupgwNmrl X-Received: from r2d2-qp.c.googlers.com ([fda3:e722:ac3:10:28:9cb1:c0a8:1652]) (user=qperret job=sendgmr) by 2002:adf:9cca:: with SMTP id h10mr3389207wre.77.1610108133066; Fri, 08 Jan 2021 04:15:33 -0800 (PST) Date: Fri, 8 Jan 2021 12:15:01 +0000 In-Reply-To: <20210108121524.656872-1-qperret@google.com> Message-Id: <20210108121524.656872-4-qperret@google.com> Mime-Version: 1.0 References: <20210108121524.656872-1-qperret@google.com> X-Mailer: git-send-email 2.30.0.284.gd98b1dd5eaa7-goog Subject: [RFC PATCH v2 03/26] arm64: kvm: Add standalone ticket spinlock implementation for use at hyp From: Quentin Perret To: Catalin Marinas , Will Deacon , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Rob Herring , Frank Rowand X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210108_071540_537757_8E27B636 X-CRM114-Status: GOOD ( 16.89 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , devicetree@vger.kernel.org, android-kvm@google.com, linux-kernel@vger.kernel.org, Fuad Tabba , David Brazdil , kernel-team@android.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Will Deacon 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 relies on the kernel's "percpu" implementation for the MCS nodes. Implement a simple ticket locking scheme based heavily on the code removed by commit c11090474d70 ("arm64: locking: Replace ticket lock implementation with qspinlock"). Signed-off-by: Will Deacon Signed-off-by: Quentin Perret --- arch/arm64/kvm/hyp/include/nvhe/spinlock.h | 92 ++++++++++++++++++++++ 1 file changed, 92 insertions(+) create mode 100644 arch/arm64/kvm/hyp/include/nvhe/spinlock.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..7584c397bbac --- /dev/null +++ b/arch/arm64/kvm/hyp/include/nvhe/spinlock.h @@ -0,0 +1,92 @@ +/* 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 + * + * 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 +#include + +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. */ + 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"); +} + +#endif /* __ARM64_KVM_NVHE_SPINLOCK_H__ */