[Qemu-devel] [Bug 1776920] Re: qemu-img convert on Mac OSX creates corrupt images

[Waldemar Kozaczuk]

I believe I have distilled entire process to few repeatable steps that
can be fully reproduced on my Mac. The binary source files - - boot.bin
and lzloader.elf - were created on my Linux VM running in VirtualBox on
same Mac but I do not think it matters as the execution completely
happens on Mac.

The steps executed on my mac:
1. dd if=boot.bin of=image.img > /dev/null 2>&1
2. dd if=lzloader.elf of=image.img conv=notrunc seek=128 > /dev/null 2>&1
3. qemu-img convert image.img -O qcow2 image.qemu
4. qemu-img convert image.qemu -O qcow2 image2.qemu

The end result:
ll image*
-rw-r--r--  1 *** *** 6684672 Jun 14 17:17 image.img
-rw-r--r--  1 *** *** 7012352 Jun 14 17:40 image.qemu
-rw-r--r--  1 *** ***  196616 Jun 14 17:40 image2.qemu

The result of regular compare:
qemu-img compare image.qemu image2.qemu
Images are identical.

The result of strict compare:
qemu-img compare -s image.qemu image2.qemu
Strict mode: Offset 0 block status mismatch!

Images are clearly different.

The same 4 steps executed on my Linux VM behave correctly - image.qemu
is TRULY identical with image2.qemu.

Qemu-img on my Mac:
qemu-img --version
qemu-img version 2.12.0
Copyright (c) 2003-2017 Fabrice Bellard and the QEMU Project developers

Details about Mac and OSX version:
Model Name:     MacBook Pro
  Model Identifier:     MacBookPro13,3
  Processor Name:       Intel Core i7
  Processor Speed:      2.7 GHz
  Number of Processors: 1
  Total Number of Cores:        4
  L2 Cache (per Core):  256 KB
  L3 Cache:     8 MB
  Memory:       16 GB

Mac filesystem:
Mount Point:    /
  File System:  APFS
  Writable:     Yes
  Ignore Ownership:     No
  BSD Name:     disk1s1
  Physical Drive:
  Device Name:  APPLE SSD SM0512L
  Media Name:   AppleAPFSMedia
  Medium Type:  SSD
  Protocol:     PCI-Express
  Internal:     Yes
  Partition Map Type:   Unknown

I am also attaching both source files and images for examination.

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https://bugs.launchpad.net/bugs/1776920

Title:
  qemu-img convert on Mac OSX creates corrupt images

Status in QEMU:
  New

Bug description:
  An image created by qemu-img create, then modified by another program
  is converted to bad/corrupt image when using convert sub command on
  Mac OSX. The same convert works on Linux. The version of qemu-img is
  2.12.

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