From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras Subject: Re: [PATCH v2] KVM: PPC: Book3s PR: Disable AIL mode with OPAL Date: Tue, 17 Jun 2014 20:15:57 +1000 Message-ID: <20140617101557.GA8790@iris.ozlabs.ibm.com> References: <1402999438-51617-1-git-send-email-agraf@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org To: Alexander Graf Return-path: Received: from ozlabs.org ([103.22.144.67]:33627 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752633AbaFQKQE (ORCPT ); Tue, 17 Jun 2014 06:16:04 -0400 Content-Disposition: inline In-Reply-To: <1402999438-51617-1-git-send-email-agraf@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Jun 17, 2014 at 12:03:58PM +0200, Alexander Graf wrote: > When we're using PR KVM we must not allow the CPU to take interrupts > in virtual mode, as the SLB does not contain host kernel mappings > when running inside the guest context. > > To make sure we get good performance for non-KVM tasks but still > properly functioning PR KVM, let's just disable AIL whenever a vcpu > is scheduled in. > > This is fundamentally different from how we deal with AIL on pSeries > type machines where we disable AIL for the whole machine as soon as > a single KVM VM is up. > > The reason for that is easy - on pSeries we do not have control over > per-cpu configuration of AIL. We also don't want to mess with CPU hotplug > races and AIL configuration, so setting it per CPU is easier and more > flexible. > > This patch fixes running PR KVM on POWER8 bare metal for me. > > Signed-off-by: Alexander Graf Acked-by: Paul Mackerras