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 B8FD1C3279B for ; Wed, 4 Jul 2018 16:21:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F31923D37 for ; Wed, 4 Jul 2018 16:21:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F31923D37 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1752684AbeGDQVH (ORCPT ); Wed, 4 Jul 2018 12:21:07 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:48358 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752165AbeGDQVF (ORCPT ); Wed, 4 Jul 2018 12:21:05 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 06932B5C7; Wed, 4 Jul 2018 16:21:05 +0000 (UTC) Received: from [10.36.117.235] (ovpn-117-235.ams2.redhat.com [10.36.117.235]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 303B17C57; Wed, 4 Jul 2018 16:21:02 +0000 (UTC) Subject: Re: [PATCH v2] KVM: Expose the split lock detection feature to guest VM To: Thomas Gleixner 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 References: <1530709593-87702-1-git-send-email-jingqi.liu@intel.com> <7813a04b-8058-538b-8c9b-cdd01ce119ac@redhat.com> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Wed, 04 Jul 2018 16:21:05 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.1]); Wed, 04 Jul 2018 16:21:05 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'pbonzini@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Paolo