From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH 1/9] pci-assign: Optionally enable 64bit BARs in guest Date: Tue, 31 Jan 2012 13:57:43 +0100 Message-ID: <4F27E547.3000809@siemens.com> References: <20120128142104.25681.93072.stgit@bling.home> <20120128142139.25681.19080.stgit@bling.home> <4F27E15A.1090800@redhat.com> <4F27E25A.1060306@siemens.com> <4F27E3C2.5050204@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Alex Williamson , "kvm@vger.kernel.org" , "shashidhar.patil@gmail.com" , "Michael S. Tsirkin" To: Avi Kivity Return-path: Received: from david.siemens.de ([192.35.17.14]:34840 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753490Ab2AaM5r (ORCPT ); Tue, 31 Jan 2012 07:57:47 -0500 In-Reply-To: <4F27E3C2.5050204@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2012-01-31 13:51, Avi Kivity wrote: > On 01/31/2012 02:45 PM, Jan Kiszka wrote: >> On 2012-01-31 13:40, Avi Kivity wrote: >>> On 01/28/2012 04:21 PM, Alex Williamson wrote: >>>> To date we've only exposed BARs as 32bit even if the device >>>> physically supports 64bit BARs. Enable 64bit BARs to be >>>> exposed as such in the guest, which may free up MMIO below >>>> 4G should the guest choose to use it. >>>> >>>> This adds a new mem64= option to pci-assign, with the >>>> default being off for testing and enablement. The goal >>>> is to eventually make this enabled by default. >>>> >>> >>> Seems fine, but do we really need the option? If it doesn't work we >>> should treat it as an ordinary but and fix it. >> >> So far it's against the architecture of the emulated system: our current >> chipset predates 64 bit PCI. >> > > Then it should be enabled/disabled at the chipset level. Makes me wonder if we already do some filtering if the device supports 64 bit but the next bridge does not. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux