From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751815AbeBZVax (ORCPT ); Mon, 26 Feb 2018 16:30:53 -0500 Received: from userp2120.oracle.com ([156.151.31.85]:51646 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751165AbeBZVav (ORCPT ); Mon, 26 Feb 2018 16:30:51 -0500 Date: Mon, 26 Feb 2018 16:30:19 -0500 From: Konrad Rzeszutek Wilk To: Borislav Petkov , x86@kernel.org, mingo@redhat.com, tglx@linutronix.de Cc: Paolo Bonzini , Wanpeng Li , LKML , kvm , Radim =?utf-8?B?S3LEjW3DocWZ?= Subject: Re: [PATCH] KVM: X86: Allow userspace to define the microcode version Message-ID: <20180226213019.GE9497@char.us.oracle.com> References: <20180226114409.GD4377@pd.tnic> <46cecef2-b0fb-b0c2-bbf3-983328d52763@redhat.com> <20180226121509.GE4377@pd.tnic> <24cd527d-5287-f0be-ffe8-eab341bf1d94@redhat.com> <3866d359-0ef8-6a99-6254-84890be62b93@redhat.com> <20180226122205.GG4377@pd.tnic> <20180226143912.GC22024@char.us.oracle.com> <20180226193711.GS4377@pd.tnic> <20180226205130.GZ22024@char.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180226205130.GZ22024@char.us.oracle.com> User-Agent: Mutt/1.8.3 (2017-05-23) X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8816 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1802260269 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 26, 2018 at 03:51:30PM -0500, Konrad Rzeszutek Wilk wrote: > On Mon, Feb 26, 2018 at 08:37:11PM +0100, Borislav Petkov wrote: > > On Mon, Feb 26, 2018 at 09:39:12AM -0500, Konrad Rzeszutek Wilk wrote: > > > diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c > > > index d19e903214b4..87d044ce837f 100644 > > > --- a/arch/x86/kernel/cpu/intel.c > > > +++ b/arch/x86/kernel/cpu/intel.c > > > @@ -144,6 +144,13 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c) > > > { > > > int i; > > > > > > + /* > > > + * We know that the hypervisor lie to us on the microcode version so > > > + * we may as well trust that it is running the correct version. > > > + */ > > > + if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) > > > > I guess > > > > cpu_has(c, X86_FEATURE_HYPERVISOR) > > > > since we're passing a ptr to the current CPU. > > Ah yes. Let me fix it up and repost. I've posted it (but I can't seem to find it on LKML). Here it is in this thread. Also adding ingo + tglrx >>From 6abac2ccf105d57d60c094950e32139e435cbefe Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Mon, 26 Feb 2018 09:35:01 -0500 Subject: [PATCH v2] x86/spectre_v2: Don't check bad microcode versions when running under hypervisors. As: 1) We know they lie about the env anyhow (host mismatch) 2) Even if the hypervisor (Xen, KVM, VMWare, etc) provided a valid "correct" value, it all gets to be very murky when migration happens (do you provide the "new" microcode of the machine?). And in reality the cloud vendors are the ones that should make sure that the microcode that is running is correct and we should just sing lalalala and trust them. CC: stable@vger.kernel.org CC: Ingo Molnar CC: "H. Peter Anvin" CC: x86@kernel.org Cc: Tom Lendacky Cc: Andi Kleen Cc: Borislav Petkov Cc: Masami Hiramatsu Cc: Arjan van de Ven Cc: David Woodhouse Signed-off-by: Konrad Rzeszutek Wilk --- v2: Change comments to be more in line with the state of the world. v3: Use cpu_has instead of boot_cpu_has per Borislav's review. --- arch/x86/kernel/cpu/intel.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index d19e903214b4..4aa9fd379390 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -144,6 +144,13 @@ static bool bad_spectre_microcode(struct cpuinfo_x86 *c) { int i; + /* + * We know that the hypervisor lie to us on the microcode version so + * we may as well hope that it is running the correct version. + */ + if (cpu_has(c, X86_FEATURE_HYPERVISOR)) + return false; + for (i = 0; i < ARRAY_SIZE(spectre_bad_microcodes); i++) { if (c->x86_model == spectre_bad_microcodes[i].model && c->x86_stepping == spectre_bad_microcodes[i].stepping) -- 2.13.4