From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sheng Yang Subject: Re: [PATCH 0/5] Lazy fpu, cr0.ts Date: Thu, 31 Dec 2009 17:23:13 +0800 Message-ID: <200912311723.13785.sheng@linux.intel.com> References: <1262190342-18611-1-git-send-email-avi@redhat.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , Joerg Roedel , kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mga07.intel.com ([143.182.124.22]:24206 "EHLO azsmga101.ch.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751305AbZLaJYb (ORCPT ); Thu, 31 Dec 2009 04:24:31 -0500 In-Reply-To: <1262190342-18611-1-git-send-email-avi@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thursday 31 December 2009 00:25:37 Avi Kivity wrote: > There are currently some inefficiencies in how we virtualize the fpu and > cr0: > > - we trap changes to cr0.ts unconditionally; however, when the guest fpu > is loaded, we're not really interested in cr0.ts (it's only needed when > the host fpu is loaded, to prevent the guest from accessing it) > - we deactivate the fpu on every guest context switch, for no reason at all > > Fix these issues by being as lazy as possible: deactivate the fpu at > heavyweight context switch time, and when the fpu is active, give the guest > ownership of cr0.ts. Looks fine to me. -- regards Yang, Sheng > > Joerg, I wasn't able to extend this to svm/npt. If we switch to the guest > with the host fpu loaded, then we must set cr0.ts and enable cr0 > intercepts. I think this is much more expensive than keeping the guest fpu > active at all times. > > Avi Kivity (5): > KVM: VMX: trace clts and lmsw instructions as cr accesses > KVM: Replace read accesses of vcpu->arch.cr0 by an accessor > KVM: VMX: Allow the guest to own some cr0 bits > KVM: Lazify fpu activation and deactivation > KVM: VMX: Give the guest ownership of cr0.ts when the fpu is active > > arch/x86/include/asm/kvm_host.h | 3 ++ > arch/x86/kvm/emulate.c | 6 ++-- > arch/x86/kvm/kvm_cache_regs.h | 12 +++++++++ > arch/x86/kvm/mmu.c | 2 +- > arch/x86/kvm/mmu.h | 2 +- > arch/x86/kvm/svm.c | 46 > ++++++++++++++++++++++-------------- arch/x86/kvm/vmx.c | > 48 ++++++++++++++++++++++++-------------- arch/x86/kvm/x86.c > | 26 ++++++++++++--------- > 8 files changed, 93 insertions(+), 52 deletions(-) >