From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:60681) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SPXNe-00046Y-Pg for qemu-devel@nongnu.org; Wed, 02 May 2012 07:06:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SPXNc-0008GH-Lh for qemu-devel@nongnu.org; Wed, 02 May 2012 07:05:58 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3074) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SPXNc-0008Fx-E5 for qemu-devel@nongnu.org; Wed, 02 May 2012 07:05:56 -0400 Message-ID: <4FA11508.2000205@redhat.com> Date: Wed, 02 May 2012 13:05:44 +0200 From: Paolo Bonzini 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> <4FA1117F.3070908@de.ibm.com> In-Reply-To: <4FA1117F.3070908@de.ibm.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: Christian Borntraeger Cc: Alexander Graf , Heinz Graalfs , qemu-devel , Markus Armbruster , Jens Freimann , Cornelia Huck , wein@linux.vnet.ibm.com, Christoph Hellwig Il 02/05/2012 12:50, Christian Borntraeger ha scritto: > 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. Ah, you never pass part of a disk to a guest and part of the same disk to another? > 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. Yes, I understood this. Paolo