From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753855AbbDGMro (ORCPT ); Tue, 7 Apr 2015 08:47:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57409 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752960AbbDGMrm (ORCPT ); Tue, 7 Apr 2015 08:47:42 -0400 Date: Tue, 7 Apr 2015 14:47:36 +0200 From: Radim =?utf-8?B?S3LEjW3DocWZ?= To: Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Marcelo Tosatti , Andy Lutomirski , stable@vger.kernel.org Subject: Re: [PATCH] x86: vdso: fix pvclock races with task migration Message-ID: <20150407124736.GA2637@potion.brq.redhat.com> References: <1428000263-11892-1-git-send-email-rkrcmar@redhat.com> <5523BB51.8090703@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5523BB51.8090703@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2015-04-07 13:11+0200, Paolo Bonzini: > On 02/04/2015 20:44, Radim Krčmář wrote: > > If we were migrated right after __getcpu, but before reading the > > migration_count, we wouldn't notice that we read TSC of a different > > VCPU, nor that KVM's bug made pvti invalid, as only migration_count > > on source VCPU is increased. > > > > Change vdso instead of updating migration_count on destination. > > > > Fixes: 0a4e6be9ca17 ("x86: kvm: Revert "remove sched notifier for cross-cpu migrations"") > > Cc: stable@vger.kernel.org > > Signed-off-by: Radim Krčmář > > Applying this, but removing the "Fixes" tag because a guest patch cannot > fix a host patch (it can work around it or complement it). I think it was correct. Both are guest only, the revert just missed some races. (0a4e6be9ca17 has misleading commit message ...)