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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,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 36258C433B4 for ; Thu, 22 Apr 2021 15:16:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F3BE561425 for ; Thu, 22 Apr 2021 15:16:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237495AbhDVPQk (ORCPT ); Thu, 22 Apr 2021 11:16:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:59028 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233106AbhDVPQj (ORCPT ); Thu, 22 Apr 2021 11:16:39 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1619104563; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=dkrS5Dxrb1ouK8VtwGEkh5+X/L5fhslUZ1usjLo8vSc=; b=GUNZNQaO/jkQoegnioQaMiAtk4QDzpmlHgZUBGMSLbFtV5BTZalH7QPEbdCNus9LoRlUVs ysPByqkQJ1gHh8KYGQagyKga5/7X7axPIJaw2sTmnDc9t7xHWPfdO7NKg19z/DNBAXKImi xIE2dkKMNRAxvhpaUYGLJSMyvWmZcOI= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7D546AF9E; Thu, 22 Apr 2021 15:16:03 +0000 (UTC) Subject: Re: [PATCH 0/3] xen: remove some checks for always present Xen features To: Juergen Gross Cc: Boris Ostrovsky , Stefano Stabellini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Peter Zijlstra , linux-kernel@vger.kernel.org, x86@kernel.org, xen-devel@lists.xenproject.org References: <20210422151007.2205-1-jgross@suse.com> From: Jan Beulich Message-ID: Date: Thu, 22 Apr 2021 17:16:03 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210422151007.2205-1-jgross@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22.04.2021 17:10, Juergen Gross wrote: > Some features of Xen can be assumed to be always present, so add a > central check to verify this being true and remove the other checks. > > Juergen Gross (3): > xen: check required Xen features > xen: assume XENFEAT_mmu_pt_update_preserve_ad being set for pv guests > xen: assume XENFEAT_gnttab_map_avail_bits being set for pv guests I wonder whether it's a good idea to infer feature presence from version numbers. If (at some point in the past) you had inferred gnttab v2 being available by version, this would have been broken by its availability becoming controllable by a command line option in Xen. Jan