Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752788AbbHaIEI (ORCPT ); Mon, 31 Aug 2015 04:04:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:52381 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751256AbbHaIEF (ORCPT ); Mon, 31 Aug 2015 04:04:05 -0400 Message-ID: <55E40A6F.5010003@redhat.com> Date: Mon, 31 Aug 2015 16:03:59 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: gleb@kernel.org, pbonzini@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, cornelia.huck@de.ibm.com Subject: Re: [PATCH V3 2/3] kvm: don't register wildcard MMIO EVENTFD on two buses References: <1440493548-2971-1-git-send-email-jasowang@redhat.com> <1440493548-2971-2-git-send-email-jasowang@redhat.com> <20150825144925-mutt-send-email-mst@redhat.com> <55DD4A5A.3080006@redhat.com> <55E3C607.1060005@redhat.com> <20150831102838-mutt-send-email-mst@redhat.com> In-Reply-To: <20150831102838-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2203 Lines: 55 On 08/31/2015 03:29 PM, Michael S. Tsirkin wrote: >>>>> Thinking more about this, invoking the 0-length write after >>>>> > >> > the != 0 length one would be better: it would mean we only >>>>> > >> > handle the userspace MMIO like this. >>> > > Right. >>> > > >> > >> > Using current unittest. This patch is about 2.9% slower than before, and >> > invoking 0-length write after is still 1.1% slower (mmio-datamatch-eventfd). >> > >> > /patch/result/-+%/ >> > /base/2957/0/ >> > /V3/3043/+2.9%/ >> > /V3+invoking != 0 length first/2990/+1.1%/ >> > >> > So looks like the best method is not searching KVM_FAST_MMIO_BUS during >> > KVM_MMIO_BUS. Instead, let userspace to register both datamatch and >> > wildcard in this case. Does this sound good to you? > No - we can't change userspace. Actually, the change was as simple as following. So I don't get the reason why. diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c index 9935029..42ee986 100644 --- a/hw/virtio/virtio-pci.c +++ b/hw/virtio/virtio-pci.c @@ -288,6 +288,8 @@ static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy, if (modern) { memory_region_add_eventfd(modern_mr, modern_addr, 2, true, n, notifier); + memory_region_add_eventfd(modern_mr, modern_addr, 0, + false, n, notifier); } if (legacy) { memory_region_add_eventfd(legacy_mr, legacy_addr, 2, @@ -297,6 +299,8 @@ static int virtio_pci_set_host_notifier_internal(VirtIOPCIProxy *proxy, if (modern) { memory_region_del_eventfd(modern_mr, modern_addr, 2, true, n, notifier); + memory_region_del_eventfd(modern_mr, modern_addr, 0, + false, n, notifier); } if (legacy) { memory_region_del_eventfd(legacy_mr, legacy_addr, 2, -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/