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Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation
From: |
Christian Borntraeger |
Subject: |
Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation |
Date: |
Wed, 02 May 2012 12:50:39 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux i686; rv:11.0) Gecko/20120412 Thunderbird/11.0.1 |
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
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation, Christian Borntraeger, 2012/05/02
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation, Paolo Bonzini, 2012/05/02
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation,
Christian Borntraeger <=
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation, Paolo Bonzini, 2012/05/02
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation, Alexander Graf, 2012/05/02
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation, Paolo Bonzini, 2012/05/02
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation, Alexander Graf, 2012/05/02
- Re: [Qemu-devel] [PATCH 1/3] Fix geometry sector calculation, Paolo Bonzini, 2012/05/02