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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 3CB6CC43613 for ; Mon, 24 Jun 2019 08:06:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18A732083D for ; Mon, 24 Jun 2019 08:06:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727047AbfFXIGV (ORCPT ); Mon, 24 Jun 2019 04:06:21 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:42761 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726809AbfFXIGV (ORCPT ); Mon, 24 Jun 2019 04:06:21 -0400 Received: by mail-wr1-f68.google.com with SMTP id x17so12782044wrl.9 for ; Mon, 24 Jun 2019 01:06:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=5Z+yhWdRmZqWnOELelg1DvCmnthpSE9A/9kI1Cr9+74=; b=M2O7elA/qfUJTE6pHfL3FC+3gkTL7zd7n/mY5j0l9u61ooNIhMS3zombFSZucNpyGX sZme1WAb+HPMm4w62txTfbsfDUoODlXLtJ8VhEIN/B7Q8H5akwGff+vvWvMXOzMO5mAO dggWFzoLmfSJrXTQcsssuOOMNN8hWsSLj5AOyzAV5O6KTV2ESXiot8xtVdbBFRsA4mwQ JcNonkRUkRkvClkg1QKzfKiwHBl8tXFZa7bHi+htOLC305C/3sbmWnRHzbUFD5Dalhuk 4vUgWYIjRDLfy6lyPXQebVr1SNiQFN7jkkshsd8iUqSXxLYmXIrN8LTF4RLm5VbB+e2i Rp6Q== X-Gm-Message-State: APjAAAXd1gltzq6NN37A0pAY0oyS9Ka4TDCFoxzkoIe4VYVkwENnJEWQ m3Pa12hXSZ1sUIg0+xW8bdrmjw== X-Google-Smtp-Source: APXvYqx2FV3+jDNBq4KGmS+pdk7ijeIAX6U+n6wy9UHW8Vgwf3IvAqW+lcidi+weRL/KtUDmo8IS4Q== X-Received: by 2002:a05:6000:4b:: with SMTP id k11mr29464510wrx.82.1561363579441; Mon, 24 Jun 2019 01:06:19 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:7822:aa18:a9d8:39ab? ([2001:b07:6468:f312:7822:aa18:a9d8:39ab]) by smtp.gmail.com with ESMTPSA id n14sm23395174wra.75.2019.06.24.01.06.18 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 24 Jun 2019 01:06:18 -0700 (PDT) Subject: Re: [RFC] perf/x86/intel: Disable check_msr for real hw To: Jiri Olsa , Andi Kleen Cc: Peter Zijlstra , Kan Liang , Jiri Olsa , David Carrillo-Cisneros , Arnaldo Carvalho de Melo , lkml , Ingo Molnar , Namhyung Kim , Alexander Shishkin , Tom Vaden , Juergen Gross , Alok Kataria References: <20190614112853.GC4325@krava> <20190621174825.GA31027@tassilo.jf.intel.com> <20190623224031.GB5471@krava> From: Paolo Bonzini Message-ID: <34c248fd-fb34-e2ae-01ae-7576694a2eff@redhat.com> Date: Mon, 24 Jun 2019 10:06:17 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190623224031.GB5471@krava> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/06/19 00:40, Jiri Olsa wrote: > On Fri, Jun 21, 2019 at 10:48:25AM -0700, Andi Kleen wrote: >> On Fri, Jun 14, 2019 at 01:28:53PM +0200, Jiri Olsa wrote: >>> hi, >>> the HPE server can do POST tracing and have enabled LBR >>> tracing during the boot, which makes check_msr fail falsly. >>> >>> It looks like check_msr code was added only to check on guests >>> MSR access, would it be then ok to disable check_msr for real >>> hardware? (as in patch below) >>> >>> We could also check if LBR tracing is enabled and make >>> appropriate checks, but this change is simpler ;-) >>> >>> ideas? thanks, >>> jirka >> >> Sorry for the late comment. I see this patch has been merged now. >> >> Unfortunately I don't think it's a good idea. The problem >> is that the hypervisor flags are only set for a few hypervisors >> that Linux knows about. But in practice there are many more >> Hypervisors around that will not cause these flags to be set. >> But these are still likely to miss MSRs. >> >> The other hypervisors are relatively obscure, but eventually >> someone will hit problems. > > any idea if there's any other flag/way we could use to detect those? There's no silver bullet, the best is boot_cpu_has(X86_FEATURE_HYPERVISOR). Paolo