From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH-next] kvm: don't try to take mmu_lock while holding the main raw kvm_lock Date: Thu, 27 Jun 2013 14:16:07 +0200 Message-ID: <51CC2D07.8080105@siemens.com> References: <1372199643-3936-1-git-send-email-paul.gortmaker@windriver.com> <20130627110911.GH18508@redhat.com> <51CC2435.7080204@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Paul Gortmaker , "linux-rt-users@vger.kernel.org" , "kvm@vger.kernel.org" To: Paolo Bonzini Return-path: Received: from david.siemens.de ([192.35.17.14]:32891 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751353Ab3F0MZr (ORCPT ); Thu, 27 Jun 2013 08:25:47 -0400 In-Reply-To: <51CC2435.7080204@redhat.com> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 2013-06-27 13:38, Paolo Bonzini wrote: > Il 27/06/2013 13:09, Gleb Natapov ha scritto: >> On Tue, Jun 25, 2013 at 06:34:03PM -0400, Paul Gortmaker wrote: >>> In commit e935b8372cf8 ("KVM: Convert kvm_lock to raw_spinlock"), >> I am copying Jan, the author of the patch. Commit message says: >> "Code under this lock requires non-preemptibility", but which code >> exactly is this? Is this still true? > > hardware_enable_nolock/hardware_disable_nolock does. IIRC, also the loop in kvmclock_cpufreq_notifier needs it because it reads the processor ID of the caller. That implies the caller cannot be preempted, but theses days a migration lock should be fine as well. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux