Re: [PATCH 1/2] pc-bios/s390-ccw/virtio-blkdev: Simplify/fix virtio_ipl_disk_is_valid()

[Thomas Huth <thuth@redhat.com>]

On 24/06/2022 11.20, Christian Borntraeger wrote:
> 
> 
> Am 24.06.22 um 10:50 schrieb Thomas Huth:
>> The s390-ccw bios fails to boot if the boot disk is a virtio-blk
>> disk with a sector size of 4096. For example:
>>
>>   dasdfmt -b 4096 -d cdl -y -p -M quick /dev/dasdX
>>   fdasd -a /dev/dasdX
>>   install a guest onto /dev/dasdX1 using virtio-blk
>>   qemu-system-s390x -nographic -hda /dev/dasdX1
> 
> Interestingly enough a real DASD (dasdX and not dasdX1) did work in the
> past and I also successfully uses an NVMe disk. So I guess the NVMe
> was 512 byte sector size then?

If you're using a full DASD, I think this was working thanks to the 
virtio_disk_is_eckd() function recognizing the geometry.

For NVMe disk - no clue. It either used 512 sectors, or it was at least 
accidentally still able to deal with the 512-byte sector requests after 
virtio_assume_scsi() "fixed" up the geometry. If you've got some spare 
minutes and still have access to those disks, it would be interesting to 
know if the boot still works there with my patches applied.

  Thomas