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 34FB3C433ED for ; Thu, 22 Apr 2021 15:16:17 +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 D2E216144A for ; Thu, 22 Apr 2021 15:16:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D2E216144A Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.115634.220658 (Exim 4.92) (envelope-from ) id 1lZb3m-0001AL-Uy; Thu, 22 Apr 2021 15:16:06 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 115634.220658; Thu, 22 Apr 2021 15:16:06 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lZb3m-0001AE-Rr; Thu, 22 Apr 2021 15:16:06 +0000 Received: by outflank-mailman (input) for mailman id 115634; Thu, 22 Apr 2021 15:16:05 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lZb3l-0001A9-AJ for xen-devel@lists.xenproject.org; Thu, 22 Apr 2021 15:16:05 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 11231367-2b32-44da-812a-6abdbb6ee2c6; Thu, 22 Apr 2021 15:16:04 +0000 (UTC) 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) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 11231367-2b32-44da-812a-6abdbb6ee2c6 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= 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 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