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[23.128.96.18]) by mx.google.com with ESMTP id k6si12011319edn.299.2020.07.14.12.32.28; Tue, 14 Jul 2020 12:32:55 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=fail header.i=@infradead.org header.s=merlin.20170209 header.b=tzoYhF+n; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729570AbgGNT3o (ORCPT + 99 others); Tue, 14 Jul 2020 15:29:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45088 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726169AbgGNT3o (ORCPT ); Tue, 14 Jul 2020 15:29:44 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4651FC061755; Tue, 14 Jul 2020 12:29:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=DxRaLkjpUaoEf0xxT682sMuthlbkUQaqou9xBSEthzs=; b=tzoYhF+ndXteGbrYuyAmg/q9ql lJtaI0FuH3c8J42sQR/E2uYkhCpFeXPc7FOgJmI68T+H7bkQ1q0y60RT2NqowxnJ3StJLPeHeFkX+ OJQuj30D3GKP79EnnrdKlWLBIRpGW8Uk7sk/geT4GGepsLX1EzHvB6k7GgVEqZNBr8+N0VDQGEOvL qCTLoXPiM68Ko3DHDHTOU+jyhW0vavjCzO+PW93pSARAtS+smk4XeVnWr5NFiSvSl/91dIrVZy0Kj 3iEsiKrDzeyxoXFNxo7ATz5CUBvlf0xCdP/0GAON2pptcLhSZ1rsMxpICMN616g+xltCbAX7YAnS8 Yffd4cvw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jvQcO-0002xP-EN; Tue, 14 Jul 2020 19:29:32 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id AA08A9817E0; Tue, 14 Jul 2020 21:29:30 +0200 (CEST) Date: Tue, 14 Jul 2020 21:29:30 +0200 From: Peter Zijlstra To: Ira Weiny Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , x86@kernel.org, Dave Hansen , Dan Williams , Vishal Verma , Andrew Morton , Fenghua Yu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [RFC PATCH 12/15] kmap: Add stray write protection for device pages Message-ID: <20200714192930.GH5523@worktop.programming.kicks-ass.net> References: <20200714070220.3500839-1-ira.weiny@intel.com> <20200714070220.3500839-13-ira.weiny@intel.com> <20200714084451.GQ10769@hirez.programming.kicks-ass.net> <20200714190615.GC3008823@iweiny-DESK2.sc.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200714190615.GC3008823@iweiny-DESK2.sc.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 14, 2020 at 12:06:16PM -0700, Ira Weiny wrote: > On Tue, Jul 14, 2020 at 10:44:51AM +0200, Peter Zijlstra wrote: > > So, if I followed along correctly, you're proposing to do a WRMSR per > > k{,un}map{_atomic}(), sounds like excellent performance all-round :-( > > Only to pages which have this additional protection, ie not DRAM. > > User mappings of this memory is not affected (would be covered by User PKeys if > desired). User mappings to persistent memory are the primary use case and the > performant path. Because performance to non-volatile memory doesn't matter? I think Dave has a better answer here ...