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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 BDE13C432C0 for ; Thu, 21 Nov 2019 23:41:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 974C3206D7 for ; Thu, 21 Nov 2019 23:41:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726695AbfKUXlV (ORCPT ); Thu, 21 Nov 2019 18:41:21 -0500 Received: from mga01.intel.com ([192.55.52.88]:39193 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725956AbfKUXlT (ORCPT ); Thu, 21 Nov 2019 18:41:19 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Nov 2019 15:41:19 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,227,1571727600"; d="scan'208";a="216242622" Received: from romley-ivt3.sc.intel.com ([172.25.110.60]) by fmsmga001.fm.intel.com with ESMTP; 21 Nov 2019 15:41:18 -0800 Date: Thu, 21 Nov 2019 15:53:29 -0800 From: Fenghua Yu To: Andy Lutomirski Cc: Christopherson Sean J , Xiaoyao Li , "Luck, Tony" , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Ingo Molnar , Borislav Petkov , H Peter Anvin , "Raj, Ashok" , "Shankar, Ravi V" , linux-kernel , x86 Subject: Re: [PATCH v10 6/6] x86/split_lock: Enable split lock detection by kernel parameter Message-ID: <20191121235329.GE199273@romley-ivt3.sc.intel.com> References: <3908561D78D1C84285E8C5FCA982C28F7F4DC167@ORSMSX115.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 21, 2019 at 03:18:46PM -0800, Andy Lutomirski wrote: > > > > On Nov 21, 2019, at 2:29 PM, Luck, Tony wrote: > > > >  > >> > >> It would be really, really nice if we could pass this feature through to a VM. Can we? > > > > It's hard because the MSR is core scoped rather than thread scoped. So on an HT > > enabled system a pair of logical processors gets enabled/disabled together. > > > > > > Well that sucks. > > Could we pass it through if the host has no HT? Debugging is *so* much easier in a VM. And HT is a bit dubious these days anyway. I think it's doable to pass it through to KVM. The difficulty is to disable split lock detection in KVM because that will disable split lock on the whole core including threads for the host. Without disabling split lock in KVM, it's doable to debug split lock in KVM. Sean and Xiaoyao are working on split lock for KVM (in separate patch set). They may have insight on how to do this. Thanks. -Fenghua