From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64718C433EF for ; Tue, 21 Jun 2022 14:50:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352075AbiFUOuU (ORCPT ); Tue, 21 Jun 2022 10:50:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1352110AbiFUOtx (ORCPT ); Tue, 21 Jun 2022 10:49:53 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 084C427CD4; Tue, 21 Jun 2022 07:49:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 82B7A616CD; Tue, 21 Jun 2022 14:49:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A41F7C341C6; Tue, 21 Jun 2022 14:49:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655822991; bh=EyNeRNlAcDveQFHhZSW52KHV2AvJzo7KCLMh5kztleU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=azjBuoUWoFfmCqiN+mAOEbU1HS1LJNHyNJLll2EsY1Gi8T+OF666Yab5NAkHdhfSn yHOBYttnyBD9Cd6Cjr0+C79E99tHuDsNiPu6cOLCAKPejBv9D3zc9YCvYVLr//XRix Hng1vfmOdOefuNiD6RzyZfHN2R400C6POuO/+1RUMstAsxmpaqewBK1e/9XAQqrYNi wV74Xjasa5HOnAWwINf8hIylNgsw5PCzaRT5qRyhIWiO25LOPwsKKriB9I+hL2XhSU 8+eXCUHbPthKiKUyZNH7yQoTMoKGJalev4Ivm+hszMvy9ipk2Qy7aB1i7Yzxr5S9DB fMNXmyKYDYUpA== From: guoren@kernel.org To: palmer@rivosinc.com, arnd@arndb.de, peterz@infradead.org, longman@redhat.com, boqun.feng@gmail.com, Conor.Dooley@microchip.com, chenhuacai@loongson.cn, kernel@xen0n.name, r@hev.cc, shorne@gmail.com Cc: linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Guo Ren , Guo Ren Subject: [PATCH V6 2/2] riscv: Add qspinlock support Date: Tue, 21 Jun 2022 10:49:20 -0400 Message-Id: <20220621144920.2945595-3-guoren@kernel.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220621144920.2945595-1-guoren@kernel.org> References: <20220621144920.2945595-1-guoren@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Guo Ren Enable qspinlock by the requirements mentioned in a8ad07e5240c9 ("asm-generic: qspinlock: Indicate the use of mixed-size atomics"). - RISC-V atomic_*_release()/atomic_*_acquire() are implemented with own relaxed version plus acquire/release_fence for RCsc synchronization. - RISC-V LR/SC pairs could provide a strong/weak forward guarantee that depends on micro-architecture. And RISC-V ISA spec has given out several limitations to let hardware support strict forward guarantee (RISC-V User ISA - 8.3 Eventual Success of Store-Conditional Instructions). Some riscv cores such as BOOMv3 & XiangShan could provide strict & strong forward guarantee (The cache line would be kept in an exclusive state for Backoff cycles, and only this core's interrupt could break the LR/SC pair). - RISC-V provides cheap atomic_fetch_or_acquire() with RCsc. - RISC-V only provides relaxed xchg16 to support qspinlock. Signed-off-by: Guo Ren Signed-off-by: Guo Ren Cc: Peter Zijlstra (Intel) Cc: Waiman Long Cc: Arnd Bergmann Cc: Palmer Dabbelt --- arch/riscv/Kconfig | 8 ++++++++ arch/riscv/include/asm/Kbuild | 2 ++ arch/riscv/include/asm/cmpxchg.h | 17 +++++++++++++++++ 3 files changed, 27 insertions(+) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 32ffef9f6e5b..e1b57cb89189 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -333,6 +333,14 @@ config NODES_SHIFT Specify the maximum number of NUMA Nodes available on the target system. Increases memory reserved to accommodate various tables. +config RISCV_USE_QUEUED_SPINLOCKS + bool "Using queued spinlock instead of ticket-lock" + depends on SMP && MMU + select ARCH_USE_QUEUED_SPINLOCKS + help + Make sure your micro arch LL/SC has a strong forward progress guarantee. + Otherwise, stay at ticket-lock. + config RISCV_ALTERNATIVE bool depends on !XIP_KERNEL diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild index 504f8b7e72d4..2cce98c7b653 100644 --- a/arch/riscv/include/asm/Kbuild +++ b/arch/riscv/include/asm/Kbuild @@ -2,7 +2,9 @@ generic-y += early_ioremap.h generic-y += flat.h generic-y += kvm_para.h +generic-y += mcs_spinlock.h generic-y += parport.h +generic-y += qspinlock.h generic-y += spinlock.h generic-y += spinlock_types.h generic-y += qrwlock.h diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h index 12debce235e5..492104d45a23 100644 --- a/arch/riscv/include/asm/cmpxchg.h +++ b/arch/riscv/include/asm/cmpxchg.h @@ -17,6 +17,23 @@ __typeof__(new) __new = (new); \ __typeof__(*(ptr)) __ret; \ switch (size) { \ + case 2: { \ + u32 temp; \ + u32 shif = ((ulong)__ptr & 2) ? 16 : 0; \ + u32 mask = 0xffff << shif; \ + __ptr = (__typeof__(ptr))((ulong)__ptr & ~(ulong)2); \ + __asm__ __volatile__ ( \ + "0: lr.w %0, %2\n" \ + " and %1, %0, %z3\n" \ + " or %1, %1, %z4\n" \ + " sc.w %1, %1, %2\n" \ + " bnez %1, 0b\n" \ + : "=&r" (__ret), "=&r" (temp), "+A" (*__ptr) \ + : "rJ" (~mask), "rJ" (__new << shif) \ + : "memory"); \ + __ret = (__ret & mask) >> shif; \ + break; \ + } \ case 4: \ __asm__ __volatile__ ( \ " amoswap.w %0, %2, %1\n" \ -- 2.36.1