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=-1.7 required=3.0 tests=DATE_IN_PAST_12_24, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT 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 1D073C169C4 for ; Wed, 30 Jan 2019 01:35:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D8E9421473 for ; Wed, 30 Jan 2019 01:35:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728335AbfA3Bfb (ORCPT ); Tue, 29 Jan 2019 20:35:31 -0500 Received: from mga04.intel.com ([192.55.52.120]:29151 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727618AbfA3Bfa (ORCPT ); Tue, 29 Jan 2019 20:35:30 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Jan 2019 17:35:30 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,538,1539673200"; d="scan'208";a="134272440" Received: from local-michael-cet-test.sh.intel.com (HELO localhost) ([10.239.159.128]) by orsmga001.jf.intel.com with ESMTP; 29 Jan 2019 17:35:27 -0800 Date: Tue, 29 Jan 2019 16:29:17 +0800 From: Yang Weijiang To: Paolo Bonzini Cc: rkrcmar@redhat.com, sean.j.christopherson@intel.com, jmattson@google.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, mst@redhat.com, yu-cheng.yu@intel.com, yi.z.zhang@intel.com, hjl.tools@gmail.com, Zhang Yi Z Subject: Re: [PATCH v2 1/7] KVM:VMX: Define CET VMCS fields and bits Message-ID: <20190129082917.GA32725@local-michael-cet-test.sh.intel.com> References: <20190122205909.24165-1-weijiang.yang@intel.com> <20190122205909.24165-2-weijiang.yang@intel.com> <5a31eef0-2b6c-bdc2-c54b-5dc4cecf084d@redhat.com> <20190128103345.GA29895@local-michael-cet-test.sh.intel.com> <4d9a5393-163b-f32a-4657-cec54093ee88@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4d9a5393-163b-f32a-4657-cec54093ee88@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 29, 2019 at 04:19:34PM +0100, Paolo Bonzini wrote: > On 28/01/19 11:33, Yang Weijiang wrote: > >> There is no code in this series to pass these fields to and from > >> userspace, and also to save/restore U_CET, INT_SSP_TAB, PL0_SSP and > >> PL3_SSP across context switches. > >> > > The kernel consumes these MSRs, please see kernel CET patch: > > https://lkml.org/lkml/fancy/2018/11/20/225 > > Still, even if the kernel saves these fields across context switch in > XSAVE areas, KVM must support accesses to the MSRs from userspace, for > example in order to perform live migration. > > For example, when reading/writing these in kvm_set_msr or > kvm_get_msr_common, you would have to do a read/write from the host > MSRs. You also have to put kvm_load_guest_fpu/kvm_put_guest_fpu calls > in __msr_io. Thanks, you're right, if we want to support live migration we need do that. However, this feature relies on quite a few external dependencies, e.g., cpu capabilities, kernel version and configuration, we don't support live migration right now. what's your opinion? > > Thanks, > > Paolo > > >> In addition, PL1_SSP and PL2_SSP should be supported even if the guest > >> doesn't use them. It makes sense to avoid intercepting them, but they > >> should still be supported and switched (possibly only if nonzero). > >> > >> Am I missing something, for example a dependency on host CET support? > >> If not, how was this series tested? > >> > > The guest CET feature is tested with kernel CET patches on internal > > virtual platform. > >