From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [RFC][PATCH] pci-assign: Drop support for raw ioport access Date: Tue, 29 May 2012 09:47:52 +0200 Message-ID: <4FC47F28.3040008@siemens.com> References: <4FC377AD.8060201@web.de> <4FC38659.8090309@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm , Alex Williamson To: Avi Kivity Return-path: Received: from goliath.siemens.de ([192.35.17.28]:18850 "EHLO goliath.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750902Ab2E2Hr5 (ORCPT ); Tue, 29 May 2012 03:47:57 -0400 In-Reply-To: <4FC38659.8090309@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2012-05-28 16:06, Avi Kivity wrote: > On 05/28/2012 04:03 PM, Jan Kiszka wrote: >> From: Jan Kiszka >> >> If the kernel does not support ioport access via sysfs, passthrough can >> only help if the unlikely case that a port <= 0x3ff is provided by the >> device. So drop this to simplify the code and to allow dropping the >> corresponding KVM infrastructure in preparation of upstream merge. >> >> Signed-off-by: Jan Kiszka >> --- >> >> Does anyone recall the precise use case this was introduced for? It >> exists since day #1, so commit logs do not help. > > At a wild guess, graphics device assignment. The only explanation now. But that requires more work anyway (e.g. to claim the VGA adapter toward the kernel). And I but we would rather do this on top of VFIO on day. > > Under what conditions would the kernel not support ioport access via sysfs? > No clue. The oldest kernel I checked (2.6.16) does not contain traces it would refuse to provide access. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux