From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755507AbcFGOHH (ORCPT ); Tue, 7 Jun 2016 10:07:07 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:51975 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753627AbcFGOHC (ORCPT ); Tue, 7 Jun 2016 10:07:02 -0400 Subject: Re: [PATCH v2 1/2] xen-pciback: return proper values during BAR sizing To: Jan Beulich , David Vrabel , Konrad Rzeszutek Wilk , Juergen Gross References: <5756857802000078000F268D@prv-mh.provo.novell.com> <5756864102000078000F269A@prv-mh.provo.novell.com> Cc: xen-devel , linux-kernel@vger.kernel.org From: Boris Ostrovsky Message-ID: <5756D4F4.7070802@oracle.com> Date: Tue, 7 Jun 2016 10:06:44 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <5756864102000078000F269A@prv-mh.provo.novell.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/07/2016 02:30 AM, Jan Beulich wrote: > Reads following writes with all address bits set to 1 should return all > changeable address bits as one, not the BAR size (nor, as was the case > for the upper half of 64-bit BARs, the high half of the region's end > address). Presumably this didn't cause any problems so far because > consumers use the value to calculate the size (usually via val & -val), > and do nothing else with it. > > But also consider the exception here: Unimplemented BARs should always > return all zeroes. > > And finally, the check for whether to return the sizing address on read > for the ROM BAR should ignore all non-address bits, not just the ROM > Enable one. Should this go to stable trees as well? -boris