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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3804CC433EF for ; Thu, 16 Jun 2022 10:12:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1376417AbiFPKMS (ORCPT ); Thu, 16 Jun 2022 06:12:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1376388AbiFPKMQ (ORCPT ); Thu, 16 Jun 2022 06:12:16 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 52FAF5D5F0; Thu, 16 Jun 2022 03:12:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=r2UDlYq5t6O5tFjJgY4OT/pXRUI5OvQVarwp5eb1G9E=; b=WZHZ0tfWmtiq3U2bqK0Hcu7UbF BZxQ9o1zxQYH9VsyHy7HWtrDu/07NB1LfbdWW5zHXi23rELYc/ihdRqz2LLyrU9N9XXwme3O+rpx9 gW/F+e+eJNeCWZ3+KkkHE1BaTXuY66cLFmdiVRSlyz+7df/xxe9EyauB5BrB1Ka/zO74ulVe5HHg9 Ph8GwTK9rwh9qOCLJCDF3D3hznAyEUedBOTpAYaVeSL/5jYSwD6koAby05D08XkazjDjYbbI3kI/f cdk8hKClwnQeltpgzW6B/qN/bS/WGCu7iCfaldBO4O5USf5oZC2U2dwhd4GCiNC881JBhkCdXONkL K9C0Jhaw==; Received: from dhcp-077-249-017-003.chello.nl ([77.249.17.3] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1o1mTu-008O7N-NK; Thu, 16 Jun 2022 10:12:07 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 3EEED301D92; Thu, 16 Jun 2022 12:12:06 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2157F2020C0EB; Thu, 16 Jun 2022 12:12:06 +0200 (CEST) Date: Thu, 16 Jun 2022 12:12:06 +0200 From: Peter Zijlstra To: Yang Weijiang Cc: pbonzini@redhat.com, seanjc@google.com, x86@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, rick.p.edgecombe@intel.com Subject: Re: [PATCH 00/19] Refresh queued CET virtualization series Message-ID: References: <20220616084643.19564-1-weijiang.yang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220616084643.19564-1-weijiang.yang@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 16, 2022 at 04:46:24AM -0400, Yang Weijiang wrote: > To minimize the impact to exiting kernel/KVM code, most of KVM patch > code can be bypassed during runtime.Uncheck "CONFIG_X86_KERNEL_IBT" > and "CONFIG_X86_SHADOW_STACK" in Kconfig before kernel build to get > rid of CET featrures in KVM. If both of them are not enabled, KVM > clears related feature bits as well as CET user bit in supported_xss, > this makes CET related checks stop at the first points. Since most of > the patch code runs on the none-hot path of KVM, it's expected to > introduce little impact to existing code. Do I understand this right in that a host without X86_KERNEL_IBT cannot run a guest with X86_KERNEL_IBT on? That seems unfortunate, since that was exactly what I did while developing the X86_KERNEL_IBT patches. I'm thinking that if the hardware supports it, KVM should expose it, irrespective of the host kernel using it.