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=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 9CE28C3A5A1 for ; Wed, 28 Aug 2019 06:09:59 +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 6B1432173E for ; Wed, 28 Aug 2019 06:09:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="TvbdzrXW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6B1432173E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+infradead-linux-riscv=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=68D2w/f6hDP8M+IrdRD5/xxU2nfOaTgfGe80G7BYAH8=; b=TvbdzrXWc2JHm0 i7YlK0+ip1uw1/qEe7Db5w/LkjnUdOl731cf2y8xgOHiajUjCe40C5dPW5eAC6XdmSmSAQX5tOK8Q 0kmKIVr2TNyox78Aj4f5tZotrhxOSKwXaVH+x1NHKcZdBPABWNXk4NnYm+2WQXtMaPx59sLLEhapZ +KhdDQyW3fNIVTf1/E4YZzAqvUbMUgo5UXr0a2XSaG0Uy9llQ4LxLe5UmNnX2b4+Ca613PJZUdgBi PIOCHVC5UEssi7D25J8zivVVux+67LLZu1CRduYoVYQS9Kr4HPmRUw4qbOCgBMsB2zC4z0NqmZlnx ny5ntlVIWqtyiAEr8bLQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i2r9U-000658-9Q; Wed, 28 Aug 2019 06:09:52 +0000 Received: from verein.lst.de ([213.95.11.211]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i2r9Q-00064Q-AZ for linux-riscv@lists.infradead.org; Wed, 28 Aug 2019 06:09:50 +0000 Received: by verein.lst.de (Postfix, from userid 2407) id 9028268AFE; Wed, 28 Aug 2019 08:09:42 +0200 (CEST) Date: Wed, 28 Aug 2019 08:09:42 +0200 From: Christoph Hellwig To: Palmer Dabbelt Subject: Re: [PATCH 8/8] riscv: ignore the SYS_RISCV_FLUSH_ICACHE_LOCAL flag Message-ID: <20190828060942.GA21592@lst.de> References: <20190822065612.28634-9-hch@lst.de> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190827_230948_519212_C627A7A0 X-CRM114-Status: GOOD ( 12.50 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-riscv@lists.infradead.org, Christoph Hellwig , Paul Walmsley Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Tue, Aug 27, 2019 at 06:10:33PM -0700, Palmer Dabbelt wrote: > This is meant to perform a context-local flush, not a cpu-local flush. The > whole point here is that userspace doesn't know anything about CPUs, just > contexts -- that's why we have this deferred flush mechanism. I think the > logic is complicated but sound, and removing this will almost certainly > lead to huge performance degradation. All calls to flush_icache_mm are local to the context. Take a look at what the current code does: - set all bits in context.icache_stale_mask - clear the current cpu from context.icache_stale_mask - flush the cpu local icache - create a local others mask containing every cpu running the context except for the current one - now if others is empty OR the local flag is set don't do anything but a memory barrier, else flush the other cpus > > Maybe I'm missing something, what is the specific issue? The issue is that the current implementation of SYS_RISCV_FLUSH_ICACHE_LOCAL only flushes the icache of the currently running core, which is an interface that can't be used correctly. riscv_flush_icache without that flag on the other handle already just flushes the caches for the cpus that run the current context, and then causes a deferred flush if the context gets run on another cpu eventually. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv