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=-5.8 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 686EEC4361B for ; Wed, 16 Dec 2020 18:00:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2632624C2C for ; Wed, 16 Dec 2020 18:00:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728756AbgLPSAM (ORCPT ); Wed, 16 Dec 2020 13:00:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44624 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728754AbgLPSAM (ORCPT ); Wed, 16 Dec 2020 13:00:12 -0500 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 521E3C0617A6; Wed, 16 Dec 2020 09:59:32 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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=Be2nf2w/Vps/TTeCXTZLGMYhjE3HrJ1GdzWfCzB412A=; b=nqy3TkxWRSI/ZUAfRjb7CiyHmI z2b0gw+/xmF3V4bRP9jBf1OEn4etLAnhng4c/UhOWUSeqB05jwPIj8Rh9uZ21hQ4ee6X60bTP9wEA RT0YNjOtLitpMmmclOBcDf+B6m0wbgQvaR8LEckSrcfDteNXNOq2baniPg2yh03WmdTFSO9hIdNUI 8E2mfDpBotw+GKCLBHJG9i8cSzTmpu4Cs3K+bLZySIc078PNlokD2esyT5D92TUH4gAPARyY3Bs4M CQ1YkaXuVJJC+yhROI4pG+byk+ORTk/MtIQmn4cU/HodbcrIdCOQPphC4Beha/FAi9+e3UzMniGn2 1KoBKrug==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kpb4K-0005dO-H8; Wed, 16 Dec 2020 17:58:32 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id ACE52300DAE; Wed, 16 Dec 2020 18:58:28 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8D62420274B26; Wed, 16 Dec 2020 18:58:28 +0100 (CET) Date: Wed, 16 Dec 2020 18:58:28 +0100 From: Peter Zijlstra To: Josh Poimboeuf Cc: =?iso-8859-1?Q?J=FCrgen_Gro=DF?= , xen-devel@lists.xenproject.org, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-hyperv@vger.kernel.org, kvm@vger.kernel.org, luto@kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Boris Ostrovsky , Stefano Stabellini , Deep Shah , "VMware, Inc." , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Daniel Lezcano , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira Subject: Re: [PATCH v2 00/12] x86: major paravirt cleanup Message-ID: <20201216175828.GQ3040@hirez.programming.kicks-ass.net> References: <20201120114630.13552-1-jgross@suse.com> <20201120125342.GC3040@hirez.programming.kicks-ass.net> <20201123134317.GE3092@hirez.programming.kicks-ass.net> <6771a12c-051d-1655-fb3a-cc45a3c82e29@suse.com> <20201215141834.GG3040@hirez.programming.kicks-ass.net> <20201215145408.GR3092@hirez.programming.kicks-ass.net> <20201216003802.5fpklvx37yuiufrt@treble> <20201216084059.GL3040@hirez.programming.kicks-ass.net> <20201216165605.4h5q7os5dutjgdqi@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201216165605.4h5q7os5dutjgdqi@treble> Precedence: bulk List-ID: X-Mailing-List: linux-hyperv@vger.kernel.org On Wed, Dec 16, 2020 at 10:56:05AM -0600, Josh Poimboeuf wrote: > On Wed, Dec 16, 2020 at 09:40:59AM +0100, Peter Zijlstra wrote: > > > Could we make it easier by caching the shared > > > per-alt-group CFI state somewhere along the way? > > > > Yes, but when I tried it grew the code required. Runtime costs would be > > less, but I figured that since alternatives are typically few and small, > > that wasn't a real consideration. > > Aren't alternatives going to be everywhere now with paravirt using them? What I meant was, they're either 2-3 wide and only a few instructions long. Which greatly bounds the actual complexity of the algorithm, however daft. > > No real objection, I just didn't do it because 1) it works, and 2) even > > moar lines. > > I'm kind of surprised it would need moar lines. Let me play around with > it and maybe I'll come around ;-) Please do, it could be getting all the niggly bits right exhausted my brain enough to miss the obvious ;-)