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=-2.3 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 1CAAEC433DF for ; Fri, 15 May 2020 12:14:06 +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 C0FA320657 for ; Fri, 15 May 2020 12:14:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="m271LPAD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C0FA320657 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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=8w3OZSfR4w3pjJAdn0TheHBJq/NA/zCl2QwzPTTuIqQ=; b=m271LPADDBcqAf pq91m4TbOEnvLWAduR+3VBP1NpujmtPU5xXQl/HedFEC/MN/pc6UwRWd6slPIS0ntZo0D9z/OnbMm WL8LHXP6Ano8ahgM7xZ/KoxtmL2VLehnEq6QO2Vgmo4H1boBXlhupusQmJklEPOk6yUPac+eJFP9S kDvIkFZ2FnF50zWqJreU7e+QCatEoq+0zctyj53Adg+GQ2lc1c9GTYKQcwpD6VRyrh8svurtPQBV+ 1hdYp33IHJ/ogmA8erj8qLm11qLQIK5YmD0FcoWB4B7Zu2tX4pjWmu8+TE0Syz9mqQRCS0CVScNH1 4ux888K5MItORmLYkitw==; 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 1jZZE4-0008S3-Ri; Fri, 15 May 2020 12:14:04 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jZZDt-0008Ke-LA for linux-arm-kernel@lists.infradead.org; Fri, 15 May 2020 12:13:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 019C11042; Fri, 15 May 2020 05:13:52 -0700 (PDT) Received: from gaia (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 56B4B3F305; Fri, 15 May 2020 05:13:50 -0700 (PDT) Date: Fri, 15 May 2020 13:13:44 +0100 From: Catalin Marinas To: Szabolcs Nagy Subject: Re: [PATCH v3 23/23] arm64: mte: Add Memory Tagging Extension documentation Message-ID: <20200515121343.GC22393@gaia> References: <20200429164705.GF30377@arm.com> <20200430162316.GJ2717@gaia> <20200504164617.GK30377@arm.com> <20200511164018.GC19176@gaia> <20200513154845.GT21779@arm.com> <20200514113722.GA1907@gaia> <20200515103839.GA22393@gaia> <20200515111359.GC27289@arm.com> <20200515112740.GB22393@gaia> <20200515120433.GE27289@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200515120433.GE27289@arm.com> 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-20200515_051353_731215_B9E33AA4 X-CRM114-Status: GOOD ( 15.39 ) 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: linux-arch@vger.kernel.org, Richard Earnshaw , nd@arm.com, Will Deacon , Andrey Konovalov , Kevin Brodsky , linux-mm@kvack.org, Vincenzo Frascino , Peter Collingbourne , Dave Martin , 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 Fri, May 15, 2020 at 01:04:33PM +0100, Szabolcs Nagy wrote: > The 05/15/2020 12:27, Catalin Marinas wrote: > > Thanks Szabolcs. While we are at this, no-one so far asked for the > > GCR_EL1.RRND to be exposed to user (and this implies RGSR_EL1.SEED). > > Since RRND=1 guarantees a distribution "no worse" than that of RRND=0, I > > thought there isn't much point in exposing this configuration to the > > user. The only advantage of RRND=0 I see is that the kernel can change > > it seems RRND=1 is the impl specific algorithm. Yes, that's the implementation specific algorithm which shouldn't be worse than the standard one. > > the seed randomly but, with only 4 bits per tag, it really doesn't > > matter much. > > > > Anyway, mentioning it here in case anyone is surprised later about the > > lack of RRND configurability. > > i'm not familiar with how irg works. It generates a random tag based on some algorithm. > is the seed per process state that's set up at process startup in some > way? or shared (and thus effectively irg is non-deterministic in > userspace)? The seed is only relevant if the standard algorithm is used (RRND=0). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel