From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 02/26] KVM: PPC: Convert MSR to shared page Date: Sun, 27 Jun 2010 11:16:43 +0300 Message-ID: <4C2708EB.9020500@redhat.com> References: <1277508314-915-1-git-send-email-agraf@suse.de> <1277508314-915-3-git-send-email-agraf@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm-ppc-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, KVM list , linuxppc-dev To: Alexander Graf Return-path: In-Reply-To: <1277508314-915-3-git-send-email-agraf-l3A5Bk7waGM@public.gmane.org> Sender: kvm-ppc-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: kvm.vger.kernel.org On 06/26/2010 02:24 AM, Alexander Graf wrote: > One of the most obvious registers to share with the guest directly is the > MSR. The MSR contains the "interrupts enabled" flag which the guest has to > toggle in critical sections. > > So in order to bring the overhead of interrupt en- and disabling down, let's > put msr into the shared page. Keep in mind that even though you can fully read > its contents, writing to it doesn't always update all state. There are a few > safe fields that don't require hypervisor interaction. See the guest > implementation that follows later for reference. > You mean, see the documentation for reference. It should be possible to write the guest code looking only at the documentation. -- error compiling committee.c: too many arguments to function