Re: [Qemu-devel] [PATCH 3/3] support host sensing of block sizes

[Christoph Hellwig]

On Thu, Apr 26, 2012 at 03:49:25PM +0200, Christian Borntraeger wrote:
> From: Einar Lueck <address@hidden>
> 
> This patch provides a new function to guess physical and logical block
> sizes and exploits them in the context of s390 virtio bus. On s390
> there may be block sizes different then 512. Therefore, we will
> use the new function to setup the physical and logical block size
> properly.
> 
> The alternative would be to do that unconditionally. There is also
> a similar approach (only the sector size) at
> https://github.com/bonzini/qemu/commit/d55b867fb6327d365c89effb7fc684459cdb26b6

The big problem with autosensing block sizes is that it breaks migration to
hosts with a block device that has a different block size, or between files
and block devices.