From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753293AbdK2VYd (ORCPT ); Wed, 29 Nov 2017 16:24:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:46626 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753216AbdK2VYa (ORCPT ); Wed, 29 Nov 2017 16:24:30 -0500 From: =?UTF-8?q?Radim=20Kr=C4=8Dm=C3=A1=C5=99?= To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Paolo Bonzini , Borislav Petkov , Alexander Graf , "Michael S. Tsirkin" , =?UTF-8?q?Jan=20H=2E=20Sch=C3=B6nherr?= , KarimAllah Ahmed , Jim Mattson Subject: [PATCH v2 1/3] KVM: x86: prevent MWAIT in guest with buggy MONITOR Date: Wed, 29 Nov 2017 22:23:41 +0100 Message-Id: <20171129212343.23167-2-rkrcmar@redhat.com> In-Reply-To: <20171129212343.23167-1-rkrcmar@redhat.com> References: <20171129212343.23167-1-rkrcmar@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 29 Nov 2017 21:24:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The bug prevents MWAIT from waking up after a write to the monitored cache line. KVM might emulate a CPU model that shouldn't have the bug, so the guest would not employ a workaround and possibly miss wakeups. Better to avoid the situation. Reviewed-by: Alexander Graf Signed-off-by: Radim Krčmář --- arch/x86/kvm/x86.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index d0b95b7a90b4..81f5f50794f6 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -281,6 +281,9 @@ static inline bool kvm_mwait_in_guest(void) return false; } + if (boot_cpu_has_bug(X86_BUG_MONITOR)) + return false; + /* * Intel CPUs without CPUID5_ECX_INTERRUPT_BREAK are problematic as * they would allow guest to stop the CPU completely by disabling -- 2.14.2