Bug 1565714

Summary: qemu 2.12.0-rc1 & rc2 report broken minimum_io_size for virtio-scsi disks
Product: [Fedora] Fedora Reporter: Richard W.M. Jones <rjones>
Component: qemuAssignee: Fedora Virtualization Maintainers <virt-maint>
Status: CLOSED RAWHIDE QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: rawhideCC: amit, berrange, cfergeau, dwmw2, itamar, pbonzini, rjones, virt-maint
Target Milestone: ---   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: qemu-2.12.0-0.7.rc3.fc29 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2018-04-16 11:18:52 UTC Type: Bug
Regression: --- Mount Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Bug Depends On:    
Bug Blocks: 910269    

Description Richard W.M. Jones 2018-04-10 15:14:13 UTC
Description of problem:

It reports a minimum_io_size of 32MB (!) instead of 512 bytes,
causing all kinds of fun and weirdness.  For example parted will
create partitions with enormous alignments, and LVM2 refuses to
work on smaller disks.

==> /sys/block/sda/queue/minimum_io_size <==                                  
33553920                                                                      

This circus is fixed by:

commit 37c51741892a89cf5710f5ac231091fb0a6352c7
Author: Fam Zheng <famz@redhat.com>
Date:   Wed Mar 28 00:41:41 2018 +0800

    scsi-disk: Don't enlarge min_io_size to max_io_size
    
    Some backends report big max_io_sectors. Making min_io_size the same
    value in this case will make it impossible for guest to align memory,
    therefore the disk may not be usable at all.
    
    Do not enlarge them when they are zero.

Version-Release number of selected component (if applicable):

qemu-2.12.0-0.5.rc1.fc29.x86_64
qemu-2.12.0-0.6.rc2.fc29.x86_64
and both affected

How reproducible:

100%

Steps to Reproduce:

$ guestfish scratch 64M : run : debug sh "cat /sys/block/sda/queue/minimum_io_size"

512 => working
33553920 => broken

Comment 1 Richard W.M. Jones 2018-04-16 11:18:52 UTC
Fix included in -rc3 package:

qemu-2.12.0-0.7.rc3.fc29

https://koji.fedoraproject.org/koji/taskinfo?taskID=26395119