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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 6B194ECDFB8 for ; Fri, 20 Jul 2018 08:02:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2A99C206B7 for ; Fri, 20 Jul 2018 08:02:18 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2A99C206B7 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728155AbeGTItS (ORCPT ); Fri, 20 Jul 2018 04:49:18 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:37558 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727176AbeGTItS (ORCPT ); Fri, 20 Jul 2018 04:49:18 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0D983401EF2E; Fri, 20 Jul 2018 08:02:15 +0000 (UTC) Received: from vitty.brq.redhat.com.redhat.com (ovpn-204-189.brq.redhat.com [10.40.204.189]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 264207C52; Fri, 20 Jul 2018 08:02:11 +0000 (UTC) From: Vitaly Kuznetsov To: Andy Lutomirski Cc: Rik van Riel , Peter Zijlstra , Andy Lutomirski , LKML , X86 ML , Mike Galbraith , kernel-team , Ingo Molnar , Dave Hansen Subject: Re: [PATCH 4/7] x86,tlb: make lazy TLB mode lazier References: <20180716190337.26133-1-riel@surriel.com> <20180716190337.26133-5-riel@surriel.com> Date: Fri, 20 Jul 2018 10:02:10 +0200 In-Reply-To: (Andy Lutomirski's message of "Thu, 19 Jul 2018 09:45:47 -0700") Message-ID: <87muumtjwd.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Fri, 20 Jul 2018 08:02:15 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Fri, 20 Jul 2018 08:02:15 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'vkuznets@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Andy Lutomirski writes: > [I added PeterZ and Vitaly -- can you see any way in which this would > break something obscure? I don't.] Thanks for CCing me, I don't see how this can break things either. At first glance, however, I'm afraid we can add performance penalty to virtualized guests which don't use native_flush_tlb_others() (Hyper-V, KVM): we will be reloading CR3 without a need as we don't look at lazy mode in PV tlb flush functions. We can either check to switch_mm_irqs_off() that native_flush_tlb_others() is in use or teach PV tlb flush functions to look at lazy mode too. (Sorry if I'm missing something important here or if this was already discussed. I just became aware of this work) [...] -- Vitaly