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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 367A8C4167B for ; Mon, 11 Dec 2023 13:40:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To:Subject: MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ai2Kr43hJB4NWwT3D8yUoXBT4oxxF2UkkitB6nYJLGA=; b=x668cyYUzBbCuk 2ktLzfeFQQOTOGhtxgl/PGRsSkeDoG/O/xDNmk412xSuKz8BO3R+4m6JORw3tCpjFMOSIaExrAhE3 Amt2pzRIul7q9a5KrdCa+l2qAfAiffrvFENDYJrYppi02iuq4hJNkG+7pp9nSFy1IoPgc9Tg1I4T7 L5FVwilfqn4zlKLzrX8RdeD0lXsCMotlfqLrbqryPH6aNsdMpGMwG+ln3Nhln8/lz7a8UgMaB3SOd qVhPO80yBe2aHrQwfgXyqnqosv3ZQNBFerO5Cg8TzWvRXHcPF/+2ifTu/66ThLI/RJ30ev+07iepI 1iiEzT/49LM6FJr/93AQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1rCgVp-004zyV-1T; Mon, 11 Dec 2023 13:39:57 +0000 Received: from smtpout.efficios.com ([167.114.26.122]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1rCgVK-004zrg-2D for linux-riscv@lists.infradead.org; Mon, 11 Dec 2023 13:39:54 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1702301965; bh=PJbq8p4AKEAVO0chtogCRS8QRlZvL+bMmeEbhWJtFRg=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=R8c6UEo0hgrynNPwVBlk6gzGqcX0sevDoK60/ZmeIgTrgQ4l25tyrEXrNmFC0ZsEC V09EaM48CuD/E+FKF1yRIqFCyVQEPrT1VsNp9XxaTz6zm/fFf976tJzdtVaoH8wJpC Wdsd6Mtc1L8zUCJr5GjJZA3tmxlz5qaEbVPfz1wUET9oM4UnZzhpL1Hqvr9viY4oax LOY+O5FomeagM0+LS1aDS/ggZ6kGU+XrkkahSnd/RJ2ARlin61ziLidOepdhtm+4J7 GZRp0J2VYnCIARwXpqWrqBbJ4YhWE+BJ7UTaZ4KsyapaCIuJ0nuWQNmREup/Fc1Dik GJixdR7GW5AeA== Received: from [172.16.0.134] (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4SpjXD5bKYzFfN; Mon, 11 Dec 2023 08:39:24 -0500 (EST) Message-ID: <05ece6bc-2a2f-40c6-b68c-a16c4b69dbef@efficios.com> Date: Mon, 11 Dec 2023 08:39:24 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] membarrier: riscv: Add full memory barrier in switch_mm() Content-Language: en-US To: Andrea Parri , paulmck@kernel.org, palmer@dabbelt.com, paul.walmsley@sifive.com, aou@eecs.berkeley.edu Cc: mmaas@google.com, hboehm@google.com, striker@us.ibm.com, charlie@rivosinc.com, rehn@rivosinc.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org References: <20231211094414.8078-1-parri.andrea@gmail.com> <20231211094414.8078-2-parri.andrea@gmail.com> From: Mathieu Desnoyers In-Reply-To: <20231211094414.8078-2-parri.andrea@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231211_053926_805627_335ACD7D X-CRM114-Status: GOOD ( 26.99 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On 2023-12-11 04:44, Andrea Parri wrote: > The membarrier system call requires a full memory barrier after storing > to rq->curr, before going back to user-space. The barrier is only > needed when switching between processes: the barrier is implied by > mmdrop() when switching from kernel to userspace, and it's not needed > when switching from userspace to kernel. > > Rely on the feature/mechanism ARCH_HAS_MEMBARRIER_CALLBACKS and on the > primitive membarrier_arch_switch_mm(), already adopted by the PowerPC > architecture, to insert the required barrier. > > Fixes: fab957c11efe2f ("RISC-V: Atomic and Locking Code") > Signed-off-by: Andrea Parri Thanks! Feel free to add those tags: Reported-by: Mathieu Desnoyers Reviewed-by: Mathieu Desnoyers > --- > MAINTAINERS | 2 +- > arch/riscv/Kconfig | 1 + > arch/riscv/include/asm/membarrier.h | 29 +++++++++++++++++++++++++++++ > arch/riscv/mm/context.c | 2 ++ > kernel/sched/core.c | 5 +++-- > 5 files changed, 36 insertions(+), 3 deletions(-) > create mode 100644 arch/riscv/include/asm/membarrier.h > > diff --git a/MAINTAINERS b/MAINTAINERS > index e2c6187a3ac80..a9166d82ffced 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -13807,7 +13807,7 @@ M: Mathieu Desnoyers > M: "Paul E. McKenney" > L: linux-kernel@vger.kernel.org > S: Supported > -F: arch/powerpc/include/asm/membarrier.h > +F: arch/*/include/asm/membarrier.h > F: include/uapi/linux/membarrier.h > F: kernel/sched/membarrier.c > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 95a2a06acc6a6..f7db95097caf1 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -27,6 +27,7 @@ config RISCV > select ARCH_HAS_GCOV_PROFILE_ALL > select ARCH_HAS_GIGANTIC_PAGE > select ARCH_HAS_KCOV > + select ARCH_HAS_MEMBARRIER_CALLBACKS > select ARCH_HAS_MMIOWB > select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE > select ARCH_HAS_PMEM_API > diff --git a/arch/riscv/include/asm/membarrier.h b/arch/riscv/include/asm/membarrier.h > new file mode 100644 > index 0000000000000..4be218fa03b14 > --- /dev/null > +++ b/arch/riscv/include/asm/membarrier.h > @@ -0,0 +1,29 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +#ifndef _ASM_RISCV_MEMBARRIER_H > +#define _ASM_RISCV_MEMBARRIER_H > + > +static inline void membarrier_arch_switch_mm(struct mm_struct *prev, > + struct mm_struct *next, > + struct task_struct *tsk) > +{ > + /* > + * Only need the full barrier when switching between processes. > + * Barrier when switching from kernel to userspace is not > + * required here, given that it is implied by mmdrop(). Barrier > + * when switching from userspace to kernel is not needed after > + * store to rq->curr. > + */ > + if (IS_ENABLED(CONFIG_SMP) && > + likely(!(atomic_read(&next->membarrier_state) & > + (MEMBARRIER_STATE_PRIVATE_EXPEDITED | > + MEMBARRIER_STATE_GLOBAL_EXPEDITED)) || !prev)) > + return; > + > + /* > + * The membarrier system call requires a full memory barrier > + * after storing to rq->curr, before going back to user-space. > + */ > + smp_mb(); > +} > + > +#endif /* _ASM_RISCV_MEMBARRIER_H */ > diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c > index 217fd4de61342..ba8eb3944687c 100644 > --- a/arch/riscv/mm/context.c > +++ b/arch/riscv/mm/context.c > @@ -323,6 +323,8 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next, > if (unlikely(prev == next)) > return; > > + membarrier_arch_switch_mm(prev, next, task); > + > /* > * Mark the current MM context as inactive, and the next as > * active. This is at least used by the icache flushing > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index a708d225c28e8..711dc753f7216 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6670,8 +6670,9 @@ static void __sched notrace __schedule(unsigned int sched_mode) > * > * Here are the schemes providing that barrier on the > * various architectures: > - * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC. > - * switch_mm() rely on membarrier_arch_switch_mm() on PowerPC. > + * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC, > + * RISC-V. switch_mm() relies on membarrier_arch_switch_mm() > + * on PowerPC and on RISC-V. > * - finish_lock_switch() for weakly-ordered > * architectures where spin_unlock is a full barrier, > * - switch_to() for arm64 (weakly-ordered, spin_unlock -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv