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 X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D234C433DF for ; Wed, 20 May 2020 09:03:28 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 21F3F20823 for ; Wed, 20 May 2020 09:03:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="nQhFnthT"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="RXz5PNeu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 21F3F20823 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=5VCvUFY1R2/ATvSku6K/hX1laHmLNgFDgUU+GjwCKQ4=; b=nQhFnthTcp0H4X PN6KME+vDr5Kz1b/PEh0+NrVfFAJ0FU20wDaLDfmWkhoWga3uVw8KZJpuvB7xqyunYcv54Wt7asts 0JlEXzjs3D9sivA2sE3be1uCQfxiIUvOyWDk1MufEz36RdBxFyvuux6Pl5dnapf/TXGuZcv4WzZ4v /Y8BrWR9FDQKYWf9MY74JUzg0QKggmMu+tSaME98WuLr+g6PAJGxoX0fUNU8jYYEqz74JRaeDm24L FZiSt6v/niF2fXpCz13xuwJGe6nuKY1dQDnthOkxGnkrzq6Xy/fJJmsrkO1Q0/rYU8nGgCZ4AFZ2f eruk73KVFSJYErcaSGiw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jbKdI-0003ZU-V9; Wed, 20 May 2020 09:03:24 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jbKdG-0003YH-QU for linux-arm-kernel@lists.infradead.org; Wed, 20 May 2020 09:03:24 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id A5815207F9; Wed, 20 May 2020 09:03:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589965402; bh=djeCigMd7GHIEFd0uJsQb94+oVAMvZcURAjv3LL4Ejc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RXz5PNeuHwLJLidx8PF8Dra/utNKJELPobHWmfa25Cue55Ern04bjX2iGxyTO/pZ6 dTDrtRX0A48mtoGeMkgcT2Q4z/zzollsHSLxJapNVe9md1r5hDSp24w3wtliHbAXPi SzbfRfVFn5YxNSFuKKPfEgRykZNinB1FccOA7d3Q= Date: Wed, 20 May 2020 10:03:18 +0100 From: Will Deacon To: Linu Cherian Subject: Re: Clarification on necessary barriers before generating IPI Message-ID: <20200520090317.GD24293@willie-the-truck> References: <20200520082856.GA24293@willie-the-truck> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200520_020322_885041_F9A37FD1 X-CRM114-Status: GOOD ( 13.54 ) 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: maz@kernel.org, Linu Cherian , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 20, 2020 at 02:23:25PM +0530, Linu Cherian wrote: > On Wed, May 20, 2020 at 1:59 PM Will Deacon wrote: > > > > On Wed, May 20, 2020 at 01:38:24PM +0530, Linu Cherian wrote: > > > How is it ensured that system register write using msr instruction(gic_send_sgi) > > > doesnt get reordered before the stores to IPI call processing > > > list(call_single_queue in kernel/smp.c), so that IPI is guaranteed to > > > be generated after the stores get completed. > > > > I think the flow is: > > > > > > DSB ST > > Dont we need an extra ISB here to ensure that the subsequent MSR SGI1R doesnt > get executed before and DSB ST ? > > This is on the assumption that DSB ST doesnt enforce the ordering of MSR SGI1R. I don't think that's a valid assumption. The architecture says: | A DSB instruction executed by a PE, PEe, completes when [...] all explicit | memory accesses of the required access types appearing in program order | before the DSB are complete for the set of observers in the required | shareability domain. and: | In addition, no instruction that appears in program order after the DSB | instruction can alter any state of the system or perform any part of its | functionality until the DSB completes other than: | | * Being fetched from memory and decoded. | * Reading the general-purpose, SIMD and floating-point, Special-purpose, or | System registers that are directly or indirectly read without causing | side-effects. Are you seeing a problem in practice? Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel