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 B6820C47089 for ; Thu, 27 May 2021 07:45:24 +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 6E8AD6139A for ; Thu, 27 May 2021 07:45:24 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6E8AD6139A 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.132859.247759 (Exim 4.92) (envelope-from ) id 1lmAhb-00041U-F4; Thu, 27 May 2021 07:45:11 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 132859.247759; Thu, 27 May 2021 07:45:11 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lmAhb-00041N-BM; Thu, 27 May 2021 07:45:11 +0000 Received: by outflank-mailman (input) for mailman id 132859; Thu, 27 May 2021 07:45:10 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lmAha-00041H-6k for xen-devel@lists.xenproject.org; Thu, 27 May 2021 07:45:10 +0000 Received: from smtp-out1.suse.de (unknown [195.135.220.28]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 15d569ad-29e7-4430-9a58-aa02a1bc0360; Thu, 27 May 2021 07:45:09 +0000 (UTC) Received: from imap.suse.de (imap-alt.suse-dmz.suse.de [192.168.254.47]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 6895C2190E; Thu, 27 May 2021 07:45:08 +0000 (UTC) Received: from director2.suse.de (director2.suse-dmz.suse.de [192.168.254.72]) by imap.suse.de (Postfix) with ESMTPSA id 2591B11A98; Thu, 27 May 2021 07:45:08 +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: 15d569ad-29e7-4430-9a58-aa02a1bc0360 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1622101508; 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=Ai0T7TEfJbqOfEVDdu1teUGkhqtkTKGVD8vLRQR8XYs=; b=iScg6lOSprfL+UF5wUInARzNGsf0XFxZMFU8BfzD9OWiy2lahSRixD5D83/PQz2isBdK6G KRe6tp9FBiRPVSjRd5+MGGcHkLwIRvIAj2K4SBTOGkj+zqsjb1fH/hO6Gs+f4cJTgksdTu 2lp49SNJM+RgRWNeg2H5hjNylk5y7l4= Subject: Re: [PATCH 04/13] cpufreq: Add Hardware P-State (HWP) driver To: Jason Andryuk Cc: Andrew Cooper , George Dunlap , Ian Jackson , Julien Grall , Stefano Stabellini , Wei Liu , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , xen-devel@lists.xenproject.org References: <20210503192810.36084-1-jandryuk@gmail.com> <20210503192810.36084-5-jandryuk@gmail.com> From: Jan Beulich Message-ID: <7fde649c-5271-72a9-5af8-b6323725d49d@suse.com> Date: Thu, 27 May 2021 09:45:04 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <20210503192810.36084-5-jandryuk@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit On 03.05.2021 21:28, Jason Andryuk wrote: > If HWP Energy_Performance_Preference isn't supported, the code falls > back to IA32_ENERGY_PERF_BIAS. Right now, we don't check > CPUID.06H:ECX.SETBH[bit 3] before using that MSR. The SDM reads like > it'll be available, and I assume it was available by the time Skylake > introduced HWP. Upon more detailed reading of the respective SDM sections, I only see two options: Either you fail driver initialization if the bit is clear, or you correctly deal with the bit being clear. If Xen runs virtualized itself, the combination of CPUID bits set may not match that of any bare metal hardware that exists. Jan