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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 908BAC282CE for ; Tue, 4 Jun 2019 04:37:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7451324BB1 for ; Tue, 4 Jun 2019 04:37:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726410AbfFDEhP (ORCPT ); Tue, 4 Jun 2019 00:37:15 -0400 Received: from mga02.intel.com ([134.134.136.20]:46171 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726136AbfFDEhP (ORCPT ); Tue, 4 Jun 2019 00:37:15 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga101.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Jun 2019 21:37:14 -0700 X-ExtLoop1: 1 Received: from unknown (HELO [10.239.13.7]) ([10.239.13.7]) by orsmga007.jf.intel.com with ESMTP; 03 Jun 2019 21:37:13 -0700 Message-ID: <5CF5F6AE.90706@intel.com> Date: Tue, 04 Jun 2019 12:42:22 +0800 From: Wei Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Eric Hankland CC: pbonzini@redhat.com, rkrcmar@redhat.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH v1] KVM: x86: PMU Whitelist References: <5CEC9667.30100@intel.com> <5CEE3AC4.3020904@intel.com> <5CF07D37.9090805@intel.com> <5CF2599B.3030001@intel.com> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 06/04/2019 01:30 AM, Eric Hankland wrote: > On Sat, Jun 1, 2019 at 3:50 AM Wei Wang wrote: >> My question is that have we proved that this indirect info leakage >> indeed happens? >> The spec states that the counter will count the related events generated by >> the logical CPU with AnyThread=0. I would be inclined to trust the >> hardware behavior >> documented in the spec unless we could prove there is a problem. > I'm not disputing the spec with regards to AnyThread=0; my point is > that LLC contention can be quantified using the PMU regardless of > whether or not you are measuring only the logical CPU you are running > on. So, I'm not sure if "quantifying LLC contention" has been proved to be a real issue. If this is considered to be an issue: - without PMU, we could also write a piece of software to run in the guest to quantify that contention (e.g. by analyzing the memory access latency). How do you prevent this? - the same thing could also happen with the L1 cache (e.g. a vCPU and a host thread run 2 logical CPUs on the same core). If this is disabled as well, we may have very few events usable, and would like to see what you have on the whitelist. Best, Wei