From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752769AbcIJGoO (ORCPT ); Sat, 10 Sep 2016 02:44:14 -0400 Received: from mx4-phx2.redhat.com ([209.132.183.25]:36952 "EHLO mx4-phx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750895AbcIJGoM (ORCPT ); Sat, 10 Sep 2016 02:44:12 -0400 Date: Sat, 10 Sep 2016 02:43:38 -0400 (EDT) From: Paolo Bonzini To: Dmitry Vyukov Cc: Robert =?utf-8?B?xZp3acSZY2tp?= , LKML , Borislav Petkov Message-ID: <347879531.10009693.1473489818957.JavaMail.zimbra@redhat.com> In-Reply-To: References: <800588f1-32d0-a4cc-821d-d31eef8921e7@redhat.com> <7810f213-c6a5-b4b7-b95d-cd9dc2570641@redhat.com> <82607566-fc73-5671-b230-4e9627e16aa3@redhat.com> Subject: Re: NULL-ptr deref in kvm_arch_vcpu_ioctl under AMD CPUs MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.4.164.1, 10.5.101.130] X-Mailer: Zimbra 8.0.6_GA_5922 (ZimbraWebClient - FF48 (Linux)/8.0.6_GA_5922) Thread-Topic: NULL-ptr deref in kvm_arch_vcpu_ioctl under AMD CPUs Thread-Index: bnknDECZonsE5r/gz8oza5W3tiiuOQ== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Hi Paolo, > > I've noticed that KVM is not actually enabled on my machines. /dev/kvm > is missing. If I mknod it manually, opens return ENODEV. > After several hours of debugging I figured that it seems to be caused by: > > commit 91fa0f8e9e2937fd9360f326ad60d51908347afd > Author: Paolo Bonzini > Date: Wed Jun 15 20:55:08 2016 +0200 > KVM: x86: always use "acknowledge interrupt on exit" > > If I move VM_EXIT_ACK_INTR_ON_EXIT from min back to opt. /dev/kvm > become functional again (at least I can open it). > > To make it clear, it all happens inside of qemu instance. I've tried > using different cpus in qemu, including "host" cpu which is pretty > capable: > > model name : Intel(R) Xeon(R) CPU E5-2690 v3 @ 2.60GHz > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov > pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm > constant_tsc arch_perfmon rep_good nopl eagerfpu pni pclmulqdq vmx > ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt > tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm > vnmi ept fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid xsaveopt > > So why am I missing VM_EXIT_ACK_INTR_ON_EXIT feature? How does it work > for other users? And how should I fix it in a proper way? You need to upgrade your host kernel to 3.16 (or possibly 3.17, but I think it's 3.16). This is a virtualization feature, and it is not provided by the processor (as is the case for "-cpu host" features); it's provided by the host kernel. Thanks, Paolo