From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: virtio PCI on KVM without IO BARs Date: Thu, 28 Feb 2013 16:43:38 +0100 Message-ID: <512F7B2A.5080108@siemens.com> References: <20130228152433.GA13832@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Alex Williamson To: "Michael S. Tsirkin" Return-path: Received: from david.siemens.de ([192.35.17.14]:26966 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754521Ab3B1Pnv (ORCPT ); Thu, 28 Feb 2013 10:43:51 -0500 In-Reply-To: <20130228152433.GA13832@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2013-02-28 16:24, Michael S. Tsirkin wrote: > Another problem with PIO is support for physical virtio devices, > and nested virt: KVM currently programs all PIO accesses > to cause vm exit, so using this device in a VM will be slow. Not answering your question, but support for programming direct PIO access into KVM's I/O bitmap would be feasible. Such feature may have some value for assigned devices that use PIO more heavily. They cause lengthy user-space exists so far. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux