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=-4.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,MAILING_LIST_MULTI,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 1CBE6C4338F for ; Wed, 25 Aug 2021 07:00:29 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 754D6611AF for ; Wed, 25 Aug 2021 07:00:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 754D6611AF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:55808 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mImtf-0001GX-Ds for qemu-devel@archiver.kernel.org; Wed, 25 Aug 2021 03:00:27 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52672) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mImt2-0000Zu-4u for qemu-devel@nongnu.org; Wed, 25 Aug 2021 02:59:48 -0400 Received: from mga12.intel.com ([192.55.52.136]:13860) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mImsz-0006SG-P7 for qemu-devel@nongnu.org; Wed, 25 Aug 2021 02:59:47 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10086"; a="197035703" X-IronPort-AV: E=Sophos;i="5.84,349,1620716400"; d="scan'208";a="197035703" Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2021 23:59:40 -0700 X-IronPort-AV: E=Sophos;i="5.84,349,1620716400"; d="scan'208";a="527104844" Received: from xiaoyaol-mobl.ccr.corp.intel.com (HELO [10.239.13.122]) ([10.239.13.122]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2021 23:59:39 -0700 To: Eduardo Habkost From: Xiaoyao Li Subject: Live migration regarding Intel PT Message-ID: Date: Wed, 25 Aug 2021 14:59:37 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.13.0 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=192.55.52.136; envelope-from=xiaoyao.li@intel.com; helo=mga12.intel.com X-Spam_score_int: -22 X-Spam_score: -2.3 X-Spam_bar: -- X-Spam_report: (-2.3 / 5.0 requ) BAYES_00=-1.9, HK_RANDOM_ENVFROM=0.928, HK_RANDOM_FROM=0.999, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , "qemu-devel@nongnu.org" , Chao Peng Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Eduardo, I have some question regrading Intel PT live migration. Commit "e37a5c7fa459 (i386: Add Intel Processor Trace feature support)" expose Intel PT with a fixed capabilities of CPUID 0x14 for live migration. And the fixed capabilities are the value reported on ICX(IceLake). However, the upcoming SPR(Sapphire Rapids) has less capabilities of INTEL_PT_CYCLE_BITMAP than ICX. It fails to enable PT in guest on SPR machine. If change the check on INTEL_PT_CYCLE_BITMAP to allow different value to allow it work on SPR. I think it breaks live migration, right? For me, not making each sub-function of PT as configurable in QEMU indeed makes it hard for live migration. Why not make PT as unmigratable in the first place when introducing the support in QEMU? Thanks, -Xiaoyao