From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras Date: Sat, 14 Sep 2013 02:03:30 +0000 Subject: Re: [PATCH 06/11] KVM: PPC: Book3S HV: Support POWER6 compatibility mode on POWER7 Message-Id: <20130914020330.GA5872@iris.ozlabs.ibm.com> List-Id: References: <20130906031003.GA29710@iris.ozlabs.ibm.com> <20130906032250.GG29710@iris.ozlabs.ibm.com> <35F61F4C-2BB2-44F9-BF35-7CD5C4251F17@suse.de> In-Reply-To: <35F61F4C-2BB2-44F9-BF35-7CD5C4251F17@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Alexander Graf Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org On Fri, Sep 13, 2013 at 02:58:43PM -0500, Alexander Graf wrote: > > How long does writing to PCR take? Is it faster than a load+branch to see whether we actually need it? I would assume the normal fast path is going to be guest cpu = host. Seems to be about 30 cycles to write PCR, so a compare and branch is faster. I'll change it. Paul. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paul Mackerras Subject: Re: [PATCH 06/11] KVM: PPC: Book3S HV: Support POWER6 compatibility mode on POWER7 Date: Sat, 14 Sep 2013 12:03:30 +1000 Message-ID: <20130914020330.GA5872@iris.ozlabs.ibm.com> References: <20130906031003.GA29710@iris.ozlabs.ibm.com> <20130906032250.GG29710@iris.ozlabs.ibm.com> <35F61F4C-2BB2-44F9-BF35-7CD5C4251F17@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: Content-Disposition: inline In-Reply-To: <35F61F4C-2BB2-44F9-BF35-7CD5C4251F17@suse.de> Sender: kvm-ppc-owner@vger.kernel.org List-Id: kvm.vger.kernel.org On Fri, Sep 13, 2013 at 02:58:43PM -0500, Alexander Graf wrote: > > How long does writing to PCR take? Is it faster than a load+branch to see whether we actually need it? I would assume the normal fast path is going to be guest cpu == host. Seems to be about 30 cycles to write PCR, so a compare and branch is faster. I'll change it. Paul.