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=-3.9 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 87D03C2D0A3 for ; Mon, 16 Nov 2020 20:17:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 05DF5217A0 for ; Mon, 16 Nov 2020 20:17:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="lv4oxCjD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732648AbgKPURT (ORCPT ); Mon, 16 Nov 2020 15:17:19 -0500 Received: from mail.skyhub.de ([5.9.137.197]:51690 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729723AbgKPURS (ORCPT ); Mon, 16 Nov 2020 15:17:18 -0500 Received: from zn.tnic (p200300ec2f07680009538f4f478c319e.dip0.t-ipconnect.de [IPv6:2003:ec:2f07:6800:953:8f4f:478c:319e]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 5B1C71EC0434; Mon, 16 Nov 2020 21:17:17 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1605557837; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=UXwBqxMoOVm+q/zWSu79fGxJWf6w8xkUF3690yPTXZ0=; b=lv4oxCjDn9K396REguIW00FqwYg5HZTtgGx1W6Eh247dUTvYcbULnNYwMeIEMUk2IDrMjt azCbeW5Uq40ay3+BjKl9kC4Obk1cvl4fBJckanDHB04uN2AK8hSYw23XSOEjt1pD8IcrnS diwiGnYZkh8iAC3gkZOqx09AYAUGEGo= Date: Mon, 16 Nov 2020 21:17:11 +0100 From: Borislav Petkov To: Alexandre Chartre Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, thomas.lendacky@amd.com, jroedel@suse.de, konrad.wilk@oracle.com, jan.setjeeilers@oracle.com, junaids@google.com, oweisse@google.com, rppt@linux.vnet.ibm.com, graf@amazon.de, mgross@linux.intel.com, kuzuno@gmail.com Subject: Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code Message-ID: <20201116201711.GE1131@zn.tnic> References: <20201116144757.1920077-1-alexandre.chartre@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20201116144757.1920077-1-alexandre.chartre@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 16, 2020 at 03:47:36PM +0100, Alexandre Chartre wrote: > This RFC proposes to defer the PTI CR3 switch until we reach C code. > The benefit is that this simplifies the assembly entry code, and make > the PTI CR3 switch code easier to understand. This also paves the way > for further possible projects such an easier integration of Address > Space Isolation (ASI), or the possibilily to execute some selected > syscall or interrupt handlers without switching to the kernel page-table What for? What is this going to be used for in the end? > (and thus avoid the PTI page-table switch overhead). Overhead of how much? Why do we care? What is the big picture justfication for this diffstat > 21 files changed, 874 insertions(+), 314 deletions(-) and the diffstat for the ASI enablement? Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette