From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56B65C43441 for ; Wed, 10 Oct 2018 16:54:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0A7232087D for ; Wed, 10 Oct 2018 16:54:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0A7232087D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726958AbeJKARE (ORCPT ); Wed, 10 Oct 2018 20:17:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50870 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726822AbeJKARD (ORCPT ); Wed, 10 Oct 2018 20:17:03 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 042E7A6E1F; Wed, 10 Oct 2018 16:54:04 +0000 (UTC) Received: from [10.36.116.237] (ovpn-116-237.ams2.redhat.com [10.36.116.237]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 2B57680D84; Wed, 10 Oct 2018 16:54:00 +0000 (UTC) Subject: Re: [PATCH v4 0/9] x86/kvm/nVMX: optimize MMU switch between L1 and L2 To: Vitaly Kuznetsov , kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Jim Mattson , Liran Alon , Sean Christopherson , linux-kernel@vger.kernel.org References: <20181008192813.30624-1-vkuznets@redhat.com> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20181008192813.30624-1-vkuznets@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Wed, 10 Oct 2018 16:54:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/10/2018 21:28, Vitaly Kuznetsov wrote: > Change since v3 [Sean Christopherson]: > - Add Reviewed-by tags (thanks!). > - Drop stale role initializer in kvm_calc_shadow_ept_root_page_role > (interim change in PATCH4, the end result is the same). > - Use '!!' instead of '!= 0' for kvm_read_cr4_bits() readings. > > Also, rebased to the current kvm/queue. > > Original description: > > Currently, when we switch from L1 to L2 (VMX) we do the following: > - Re-initialize L1 MMU as shadow EPT MMU (nested_ept_init_mmu_context()) > - Re-initialize 'nested' MMU (nested_vmx_load_cr3() -> init_kvm_nested_mmu()) > > When we switch back we do: > - Re-initialize L1 MMU (nested_vmx_load_cr3() -> init_kvm_tdp_mmu()) > > This seems to be sub-optimal. Initializing MMU is expensive (thanks to > update_permission_bitmask(), update_pkru_bitmask(),..) Try solving the > issue by splitting L1-normal and L1-nested MMUs and checking if MMU reset > is really needed. This spares us about 1000 cpu cycles on nested vmexit. > > Brief look at SVM makes me think it can be optimized the exact same way, > I'll do this in a separate series. > > Paolo Bonzini (1): > x86/kvm/mmu: get rid of redundant kvm_mmu_setup() > > Vitaly Kuznetsov (8): > x86/kvm/mmu: make vcpu->mmu a pointer to the current MMU > x86/kvm/mmu.c: set get_pdptr hook in kvm_init_shadow_ept_mmu() > x86/kvm/mmu.c: add kvm_mmu parameter to kvm_mmu_free_roots() > x86/kvm/mmu: introduce guest_mmu > x86/kvm/mmu: make space for source data caching in struct kvm_mmu > x86/kvm/nVMX: introduce source data cache for > kvm_init_shadow_ept_mmu() > x86/kvm/mmu: check if tdp/shadow MMU reconfiguration is needed > x86/kvm/mmu: check if MMU reconfiguration is needed in > init_kvm_nested_mmu() > > arch/x86/include/asm/kvm_host.h | 44 +++- > arch/x86/kvm/mmu.c | 357 +++++++++++++++++++------------- > arch/x86/kvm/mmu.h | 8 +- > arch/x86/kvm/mmu_audit.c | 12 +- > arch/x86/kvm/paging_tmpl.h | 15 +- > arch/x86/kvm/svm.c | 14 +- > arch/x86/kvm/vmx.c | 55 +++-- > arch/x86/kvm/x86.c | 22 +- > 8 files changed, 322 insertions(+), 205 deletions(-) > Queued, thanks. Paolo