From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:57499) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SPXIv-0002VB-Nx for qemu-devel@nongnu.org; Wed, 02 May 2012 07:01:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SPXIp-0006Z9-Cq for qemu-devel@nongnu.org; Wed, 02 May 2012 07:01:05 -0400 Received: from e06smtp18.uk.ibm.com ([195.75.94.114]:40917) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SPXIp-0006Z3-3U for qemu-devel@nongnu.org; Wed, 02 May 2012 07:00:59 -0400 Received: from /spool/local by e06smtp18.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 2 May 2012 12:00:56 +0100 Received: from d06av10.portsmouth.uk.ibm.com (d06av10.portsmouth.uk.ibm.com [9.149.37.251]) by d06nrmr1707.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q42B0mAj2322442 for ; Wed, 2 May 2012 12:00:48 +0100 Received: from d06av10.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av10.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q42Au960022792 for ; Wed, 2 May 2012 06:56:12 -0400 Message-ID: <4FA1117F.3070908@de.ibm.com> Date: Wed, 02 May 2012 12:50:39 +0200 From: Christian Borntraeger MIME-Version: 1.0 References: <1335448165-26174-1-git-send-email-borntraeger@de.ibm.com> <1335448165-26174-2-git-send-email-borntraeger@de.ibm.com> <4F9AC55F.5000101@redhat.com> <4FA109F6.3090107@de.ibm.com> <4FA10B9F.9040909@redhat.com> In-Reply-To: <4FA10B9F.9040909@redhat.com> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: Alexander Graf , Heinz Graalfs , qemu-devel , Markus Armbruster , Jens Freimann , Cornelia Huck , wein@linux.vnet.ibm.com, Christoph Hellwig On 02/05/12 12:25, Paolo Bonzini wrote: > Il 02/05/2012 12:18, Christian Borntraeger ha scritto: >> Maybe that really points to the problem that we are trying to solve here. >> For a dasd device, there is usually a 4096 byte block size and on the host >> these 4096 arereported via getss and getpbsz. >> The geometry reported by the device driver is usually 15 head and 12 sectors >> per track, but actually means 12 sectors of 4096 bytes size (a track ~ 48k). >> >> What I want to achieve is that the guest view is identical to the host view >> for cyls, heads, secs, and all block sizes. > > I think what you want is _not_ to have the same view as the host. What > you want is simply to have a default that is consistent with what is > common on actual s390 disks. Let me put it in another way: I want to have these values to match the _device_ that we are passing to the guest because several tools and the partition detection code for a compatible disk format (those that can be accessed by z/OS) needs those values to work properly. That of course means that the guest view is identical to the host view because both views describe a real property of the hardware. IOW the geometry for dasd devices is not an artifical number, it has some real meaning that has a influence on the data structures on the disk. Thing is, the easiest way of getting the hardware property is to query the host. Does that make the situation a bit clearer? Christian