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=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 191EBC43331 for ; Sun, 10 Nov 2019 12:44:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E566320B7C for ; Sun, 10 Nov 2019 12:44:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726684AbfKJMnx (ORCPT ); Sun, 10 Nov 2019 07:43:53 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:54559 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726301AbfKJMnw (ORCPT ); Sun, 10 Nov 2019 07:43:52 -0500 Received: from p5b06da22.dip0.t-ipconnect.de ([91.6.218.34] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1iTmZI-0005Vb-8n; Sun, 10 Nov 2019 13:43:48 +0100 Date: Sun, 10 Nov 2019 13:43:46 +0100 (CET) From: Thomas Gleixner To: Andy Lutomirski cc: Andy Lutomirski , Peter Zijlstra , LKML , x86@kernel.org, Stephen Hemminger , Willy Tarreau , Juergen Gross , Sean Christopherson , Linus Torvalds , "H. Peter Anvin" Subject: Re: [patch 4/9] x86/io: Speedup schedule out of I/O bitmap user In-Reply-To: <53B49BD3-6F9C-4A78-B203-1BD53034014D@amacapital.net> Message-ID: References: <53B49BD3-6F9C-4A78-B203-1BD53034014D@amacapital.net> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323329-894609131-1573389828=:12583" X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-894609131-1573389828=:12583 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT On Fri, 8 Nov 2019, Andy Lutomirski wrote: > > On Nov 8, 2019, at 3:45 PM, Thomas Gleixner wrote: > > On Fri, 8 Nov 2019, Andy Lutomirski wrote: > >> SDM vol 3 27.5.2 says the BUILD_BUG_ON is right. Or am I > >> misunderstanding you? > >> > >> I'm reasonably confident that the TSS limit is indeed 0x67 after VM > >> exit, and I wrote the existing code that tries to optimize this to avoid > >> LTR when not needed. > > > > The BUILD_BUG_ON(IO_BITMAP_OFFSET - 1 == 0x67) in the VMX code is bogus in > > two aspects: > > > > 1) This wants to be in generic x86 code > > I think disagree. The only thing special about 0x67 is that VMX hard > codes it. It’s specifically a VMX-ism. So I think the VMX code should > indeed assert that 0x67 is a safe value. Yes, it is a VMX specific issue, but I really prefer the build to fail in the common code without having to enable VMX if something changes the TSS layout in incompatible ways. Thanks, tglx --8323329-894609131-1573389828=:12583--