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=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,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 2EF11C433ED for ; Fri, 23 Apr 2021 12:42:02 +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 C39D9613C9 for ; Fri, 23 Apr 2021 12:42:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C39D9613C9 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.116279.221936 (Exim 4.92) (envelope-from ) id 1lZv7n-0008LF-0J; Fri, 23 Apr 2021 12:41:35 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 116279.221936; Fri, 23 Apr 2021 12:41:34 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lZv7m-0008L8-Tf; Fri, 23 Apr 2021 12:41:34 +0000 Received: by outflank-mailman (input) for mailman id 116279; Fri, 23 Apr 2021 12:41:34 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lZv7m-0008L3-5g for xen-devel@lists.xenproject.org; Fri, 23 Apr 2021 12:41:34 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id c8e91387-2ff0-456f-9102-d8a6a9ba9337; Fri, 23 Apr 2021 12:41:33 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4FDE2AEE6; Fri, 23 Apr 2021 12:41:32 +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: c8e91387-2ff0-456f-9102-d8a6a9ba9337 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=1619181692; 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=BVXqAVlxN1DIDsUMgbfYFCdB+fBZrqicM6ufIbegZZU=; b=JeSOKFR/XMYtvEStzDY9K6yBYiJf3US6LS8r3aZRfCFFqOyHAb8pRM6toLBo59FADDK+io Xjukt13/nS0/kzJ+hoGjaEow5JuUUcLwAGVq/idwo8km+FOea8v3vnwIaNTk8FcVVVRsvK J/LCvq/qWDXnZFl0lrwZm4EdDQ8rmE8= Subject: Re: [PATCH] x86/cpuid: do not expand max leaves on restore To: Roger Pau Monne Cc: Ian Jackson , Wei Liu , Andrew Cooper , xen-devel@lists.xenproject.org References: <20210423105408.7265-1-roger.pau@citrix.com> From: Jan Beulich Message-ID: <91a32d56-c0cd-f883-eee5-de2691417703@suse.com> Date: Fri, 23 Apr 2021 14:41:32 +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: <20210423105408.7265-1-roger.pau@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 23.04.2021 12:54, Roger Pau Monne wrote: > When restoring limit the maximum leaves to the ones supported by Xen > 4.13 in order to not expand the maximum leaf a guests sees. Note this > is unlikely to cause real issues. Why 4.13 (and not 4.12) here when ... > Guests restored from Xen versions 4.13 or greater will contain CPUID > data on the stream that will override the values set by > xc_cpuid_apply_policy. ... 4.13 already communicates the values? > --- a/tools/libs/guest/xg_cpuid_x86.c > +++ b/tools/libs/guest/xg_cpuid_x86.c > @@ -510,6 +510,11 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore, > { > p->feat.mpx = test_bit(X86_FEATURE_MPX, host_featureset); > } > + > + /* Clamp maximum leaves to the supported ones on 4.13. */ Same aspect here then. (While not being a native speaker, it would still seem to me that flipping "supported" and "ones" would read slightly more clearly.) > + p->basic.max_leaf = min(p->basic.max_leaf, 0xdu); > + p->feat.max_subleaf = min(p->feat.max_subleaf, 1u); > + p->extd.max_leaf = min(p->extd.max_leaf, 0x1cu); > } With this I think the comment ahead of the enclosing if() wants either amending or moving immediately inside the if()'s body. Jan