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_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 26253C3279B for ; Wed, 4 Jul 2018 18:40:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D129C21354 for ; Wed, 4 Jul 2018 18:40:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D129C21354 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752816AbeGDSkF (ORCPT ); Wed, 4 Jul 2018 14:40:05 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:48398 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752218AbeGDSkE (ORCPT ); Wed, 4 Jul 2018 14:40:04 -0400 Received: from hsi-kbw-5-158-153-52.hsi19.kabel-badenwuerttemberg.de ([5.158.153.52] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1famh0-00045a-7y; Wed, 04 Jul 2018 20:39:54 +0200 Date: Wed, 4 Jul 2018 20:39:50 +0200 (CEST) From: Thomas Gleixner To: Paolo Bonzini cc: Jingqi Liu , rkrcmar@redhat.com, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, wei.w.wang@intel.com, Robert Hoo Subject: Re: [PATCH v2] KVM: Expose the split lock detection feature to guest VM In-Reply-To: Message-ID: References: <1530709593-87702-1-git-send-email-jingqi.liu@intel.com> <7813a04b-8058-538b-8c9b-cdd01ce119ac@redhat.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 4 Jul 2018, Paolo Bonzini wrote: > On 04/07/2018 16:51, Thomas Gleixner wrote: > > There is no rush for this to be in KVM/QEMU now because all what exists for > > this new split lock thing is 'silicon' running on an emulator. And w/o > > support in the kernel proper this is completely useless. > > That's good. I assumed it was IceLake, in which case the feature would > block the definition of a standard IceLake CPU model in QEMU. > > > So this needs the following things: > > > > 1) Proper enumeration via CPUID or MISC_FEATURES. The current detection > > hack is just broken. > > Yes please. > > > 2) A proper host side implementation, which then automatically makes the > > stuff usable in a guest once it is exposed. > > If the CPUID bit or MISC_FEATURES is added, you don't even need the host > side for the guests to use it. It's only needed now because of the ugly > MSR-based detection. > > > 3) A proper way how to expose MSR_TEST_CTL to the guest, but surely not > > with extra split_lock_ctrl voodoo. It's an MSR nothing else. KVM/QEMU > > have standartized ways to deal with MSRs and the required selective > > bitwise access control. > > That part is pretty much standard, I'm not worried about it. We have > one variable in struct kvm_vcpu_arch for each MSR (or set of MSRs) that > we expose, so that's the split_lock_ctrl voodoo. :) > > Once the detection is sorted out, KVM is easy. That's what I thought and even if it was IceLeak then they still can flip a CPUID/MISC FEATURE bit in their binary BIOS blob or ucode. We really need to push back hard on these half baken features which need voodoo programming to detect. Thanks, tglx