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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,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 BC14DC433DB for ; Mon, 1 Mar 2021 09:10:14 +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 7952864E01 for ; Mon, 1 Mar 2021 09:10:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7952864E01 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.91370.172701 (Exim 4.92) (envelope-from ) id 1lGeZ3-0005rD-4D; Mon, 01 Mar 2021 09:10:05 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 91370.172701; Mon, 01 Mar 2021 09:10:05 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lGeZ3-0005qU-0a; Mon, 01 Mar 2021 09:10:05 +0000 Received: by outflank-mailman (input) for mailman id 91370; Mon, 01 Mar 2021 09:10:04 +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 1lGeZ2-0005nq-5u for xen-devel@lists.xenproject.org; Mon, 01 Mar 2021 09:10:04 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 5519d4c5-4ea9-42a2-80c8-e3895efc59c6; Mon, 01 Mar 2021 09:10:03 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5FBC9ADDD; Mon, 1 Mar 2021 09:10:02 +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: 5519d4c5-4ea9-42a2-80c8-e3895efc59c6 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=1614589802; 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=vpIjoIF/4xtxEiq/P5y5V6xvRl0P36DV4+b9ggmFKIQ=; b=YmvxN6IETBxbloKnrf2S22U4ieQ79m+hQjLPXANTsJS8n66Tk18VTuztopoG+w84GGhrj+ L2MePqSnNVzUsJeBGXR8M8lfe0t130aBsrxihH/bhZiwwpUT+uJhuzpXNSX7fTNicw+v8S Nco5abfWeNjAvMsSGi+lJFP6/ObX1FY= Subject: Re: [PATCH v2] xen: introduce XENFEAT_direct_mapped and XENFEAT_not_direct_mapped To: Stefano Stabellini Cc: Stefano Stabellini , andrew.cooper3@citrix.com, julien@xen.org, xen-devel@lists.xenproject.org References: <20210226225217.2137-1-sstabellini@kernel.org> From: Jan Beulich Message-ID: Date: Mon, 1 Mar 2021 10:10:01 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210226225217.2137-1-sstabellini@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 26.02.2021 23:52, Stefano Stabellini wrote: > Introduce two feature flags to tell the domain whether it is > direct-mapped or not. It allows the guest kernel to make informed > decisions on things such as swiotlb-xen enablement. > > The introduction of both flags (XENFEAT_direct_mapped and > XENFEAT_not_direct_mapped) allows the guest kernel to avoid any > guesswork if one of the two is present, or fallback to the current > checks if neither of them is present. > > XENFEAT_direct_mapped is always set for not auto-translated guests. > > For auto-translated guests, only Dom0 on ARM is direct-mapped. Also, > see is_domain_direct_mapped() which refers to auto-translated guests: > xen/include/asm-arm/domain.h:is_domain_direct_mapped > xen/include/asm-x86/domain.h:is_domain_direct_mapped > > Signed-off-by: Stefano Stabellini Reviewed-by: Jan Beulich preferably with one cosmetic aspect taken care of: > --- a/xen/common/kernel.c > +++ b/xen/common/kernel.c > @@ -560,6 +560,10 @@ DO(xen_version)(int cmd, XEN_GUEST_HANDLE_PARAM(void) arg) > (1U << XENFEAT_hvm_callback_vector) | > (has_pirq(d) ? (1U << XENFEAT_hvm_pirqs) : 0); > #endif > + if ( is_domain_direct_mapped(d) || !paging_mode_translate(d) ) While I realize the left side of the || is what you're after, I'd generally see the more common/universal/whatever-you-want- to-call-it condition be checked first, and the most special purpose one last. IOW I'd prefer if both side of the || could be swapped. Jan