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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 4B8BDC3815B for ; Mon, 20 Apr 2020 14:13:08 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 238A120B1F for ; Mon, 20 Apr 2020 14:13:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 238A120B1F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jQXAM-0004v9-Bw; Mon, 20 Apr 2020 14:12:54 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1jQXAK-0004v4-QH for xen-devel@lists.xenproject.org; Mon, 20 Apr 2020 14:12:52 +0000 X-Inumbo-ID: 05883850-8311-11ea-83d8-bc764e2007e4 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 05883850-8311-11ea-83d8-bc764e2007e4; Mon, 20 Apr 2020 14:12:52 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id BC2B2AC44; Mon, 20 Apr 2020 14:12:50 +0000 (UTC) Subject: Re: [PATCH 3/3] x86/pv: Compile out compat_gdt in !CONFIG_PV builds To: Andrew Cooper References: <20200417155004.16806-1-andrew.cooper3@citrix.com> <20200417155004.16806-4-andrew.cooper3@citrix.com> From: Jan Beulich Message-ID: <3c8eee8d-c2ce-d262-4056-a5d2c9f843cb@suse.com> Date: Mon, 20 Apr 2020 16:12:49 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200417155004.16806-4-andrew.cooper3@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Xen-devel , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On 17.04.2020 17:50, Andrew Cooper wrote: > There is no need for the Compat GDT if there are no 32bit PV guests. This > saves 4k per online CPU > > Bloat-o-meter reports the following savings in Xen itself: > > add/remove: 0/3 grow/shrink: 1/4 up/down: 7/-4612 (-4605) > Function old new delta > cpu_smpboot_free 1249 1256 +7 > per_cpu__compat_gdt_l1e 8 - -8 > per_cpu__compat_gdt 8 - -8 > init_idt_traps 442 420 -22 > load_system_tables 414 364 -50 > trap_init 444 280 -164 > cpu_smpboot_callback 1255 991 -264 > boot_compat_gdt 4096 - -4096 > Total: Before=3062726, After=3058121, chg -0.15% > > Signed-off-by: Andrew Cooper > --- > CC: Jan Beulich > CC: Wei Liu > CC: Roger Pau Monné > > The increase in cpu_smpboot_free() appears to be a consequence of a totally > different layout of basic blocks. > --- > xen/arch/x86/cpu/common.c | 5 +++-- > xen/arch/x86/desc.c | 2 ++ > xen/arch/x86/smpboot.c | 5 ++++- > xen/arch/x86/traps.c | 10 +++++++--- > 4 files changed, 16 insertions(+), 6 deletions(-) > > diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c > index 1b33f1ed71..7b093cb421 100644 > --- a/xen/arch/x86/cpu/common.c > +++ b/xen/arch/x86/cpu/common.c > @@ -752,8 +752,9 @@ void load_system_tables(void) > > _set_tssldt_desc(gdt + TSS_ENTRY, (unsigned long)tss, > sizeof(*tss) - 1, SYS_DESC_tss_avail); > - _set_tssldt_desc(compat_gdt + TSS_ENTRY, (unsigned long)tss, > - sizeof(*tss) - 1, SYS_DESC_tss_busy); > + if ( IS_ENABLED(CONFIG_PV32) ) > + _set_tssldt_desc(compat_gdt + TSS_ENTRY, (unsigned long)tss, > + sizeof(*tss) - 1, SYS_DESC_tss_busy); Wouldn't this better be "if ( opt_pv32 )"? Also elsewhere then. Jan