From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752764AbeCPEk2 (ORCPT ); Fri, 16 Mar 2018 00:40:28 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:37940 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750748AbeCPEk1 (ORCPT ); Fri, 16 Mar 2018 00:40:27 -0400 Date: Fri, 16 Mar 2018 12:40:17 +0800 From: Peter Xu To: Alex Williamson Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, eric.auger@redhat.com, aik@ozlabs.ru Subject: Re: [PATCH v2 3/3] vfio/pci: Add ioeventfd support Message-ID: <20180316044017.GC2477@xz-mi> References: <20180315212634.15150.88094.stgit@gimli.home> <20180315213157.15150.86812.stgit@gimli.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20180315213157.15150.86812.stgit@gimli.home> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2018 at 03:31:58PM -0600, Alex Williamson wrote: > The ioeventfd here is actually irqfd handling of an ioeventfd such as > supported in KVM. A user is able to pre-program a device write to > occur when the eventfd triggers. This is yet another instance of > eventfd-irqfd triggering between KVM and vfio. The impetus for this > is high frequency writes to pages which are virtualized in QEMU. > Enabling this near-direct write path for selected registers within > the virtualized page can improve performance and reduce overhead. > Specifically this is initially targeted at NVIDIA graphics cards where > the driver issues a write to an MMIO register within a virtualized > region in order to allow the MSI interrupt to re-trigger. > > Signed-off-by: Alex Williamson Reviewed-by: Peter Xu -- Peter Xu