From mboxrd@z Thu Jan 1 00:00:00 1970 From: Scott Wood Date: Tue, 04 Jun 2013 22:53:52 +0000 Subject: Re: [RFC PATCH 6/6] KVM: PPC: Book3E: Enhance FPU laziness Message-Id: <1370386432.748.22@snotra> List-Id: References: <1370292868-2697-7-git-send-email-mihai.caraman@freescale.com> In-Reply-To: <1370292868-2697-7-git-send-email-mihai.caraman@freescale.com> (from mihai.caraman@freescale.com on Mon Jun 3 15:54:28 2013) MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Mihai Caraman Cc: kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Mihai Caraman On 06/03/2013 03:54:28 PM, Mihai Caraman wrote: > Adopt AltiVec approach to increase laziness by calling > kvmppc_load_guest_fp() > just before returning to guest instaed of each sched in. > > Signed-off-by: Mihai Caraman If you did this *before* adding Altivec it would have saved a question in an earlier patch. :-) > --- > arch/powerpc/kvm/booke.c | 1 + > arch/powerpc/kvm/e500mc.c | 2 -- > 2 files changed, 1 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c > index 019496d..5382238 100644 > --- a/arch/powerpc/kvm/booke.c > +++ b/arch/powerpc/kvm/booke.c > @@ -1258,6 +1258,7 @@ int kvmppc_handle_exit(struct kvm_run *run, > struct kvm_vcpu *vcpu, > } else { > kvmppc_lazy_ee_enable(); > kvmppc_load_guest_altivec(vcpu); > + kvmppc_load_guest_fp(vcpu); > } > } > You should probably do these before kvmppc_lazy_ee_enable(). Actually, I don't think this is a good idea at all. As I understand it, you're not supposed to take kernel ownersship of floating point in non-atomic context, because an interrupt could itself call enable_kernel_fp(). Do you have benchmarks showing it's even worthwhile? -Scott