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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 4A813C3276C for ; Fri, 3 Jan 2020 01:12:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 237462085B for ; Fri, 3 Jan 2020 01:12:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727267AbgACBMT (ORCPT ); Thu, 2 Jan 2020 20:12:19 -0500 Received: from mga06.intel.com ([134.134.136.31]:48945 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725872AbgACBMS (ORCPT ); Thu, 2 Jan 2020 20:12:18 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Jan 2020 17:12:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.69,388,1571727600"; d="scan'208";a="221511534" Received: from joy-optiplex-7040.sh.intel.com ([10.239.13.9]) by orsmga006.jf.intel.com with ESMTP; 02 Jan 2020 17:12:16 -0800 From: Yan Zhao To: zhenyuw@linux.intel.com Cc: alex.williamson@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, intel-gvt@eclists.intel.com, pbonzini@redhat.com, kevin.tian@intel.com, Yan Zhao Subject: [PATCH 2/2] drm/i915/gvt: subsitute kvm_read/write_guest with vfio_iova_rw Date: Thu, 2 Jan 2020 20:03:49 -0500 Message-Id: <20200103010349.4262-1-yan.y.zhao@intel.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200103010055.4140-1-yan.y.zhao@intel.com> References: <20200103010055.4140-1-yan.y.zhao@intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As a device model, it is better to read/write guest memory using vfio interface, so that vfio is able to maintain dirty info of device IOVAs. Compared to CPU side interfaces kvm_read/write_guest(), vfio_iova_rw() has ~600 cycles more overhead on average. ------------------------------------- | interface | avg cpu cycles | |-----------------------------------| | kvm_write_guest | 1546 | | ----------------------------------| | kvm_read_guest | 686 | |-----------------------------------| | vfio_iova_rw(w) | 2233 | |-----------------------------------| | vfio_iova_rw(r) | 1262 | ------------------------------------- Comparison of benchmarks scores are as blow: --------------------------------------------------------- | avg score | kvm_read/write_guest | vfio_iova_rw | --------------------------------------------------------- | Glmark2 | 1132 | 1138.2 | --------------------------------------------------------- | Lightsmark | 61.558 | 61.538 | |-------------------------------------------------------- | OpenArena | 142.77 | 136.6 | --------------------------------------------------------- | Heaven | 698 | 686.8 | -------------------------------------------------------- No obvious performance downgrade found. Cc: Kevin Tian Signed-off-by: Yan Zhao --- drivers/gpu/drm/i915/gvt/kvmgt.c | 26 +++++++------------------- 1 file changed, 7 insertions(+), 19 deletions(-) diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c b/drivers/gpu/drm/i915/gvt/kvmgt.c index bd79a9718cc7..576b05db3998 100644 --- a/drivers/gpu/drm/i915/gvt/kvmgt.c +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c @@ -1966,31 +1966,19 @@ static int kvmgt_rw_gpa(unsigned long handle, unsigned long gpa, void *buf, unsigned long len, bool write) { struct kvmgt_guest_info *info; - struct kvm *kvm; - int idx, ret; - bool kthread = current->mm == NULL; + int ret; + struct intel_vgpu *vgpu; + struct device *dev; if (!handle_valid(handle)) return -ESRCH; info = (struct kvmgt_guest_info *)handle; - kvm = info->kvm; - - if (kthread) { - if (!mmget_not_zero(kvm->mm)) - return -EFAULT; - use_mm(kvm->mm); - } - - idx = srcu_read_lock(&kvm->srcu); - ret = write ? kvm_write_guest(kvm, gpa, buf, len) : - kvm_read_guest(kvm, gpa, buf, len); - srcu_read_unlock(&kvm->srcu, idx); + vgpu = info->vgpu; + dev = mdev_dev(vgpu->vdev.mdev); - if (kthread) { - unuse_mm(kvm->mm); - mmput(kvm->mm); - } + ret = write ? vfio_iova_rw(dev, gpa, buf, len, true) : + vfio_iova_rw(dev, gpa, buf, len, false); return ret; } -- 2.17.1