qemu failure in -next due to 'ide: Fix interface autodetection in legacy IDE driver (trial #2)'

[Guenter Roeck <linux@roeck-us.net>]

Hi,

my qemu isapc tests on -next started to fail with next-20170103.
The relevant log is as follows.

VFS: Cannot open root device "hda" or unknown-block(0,0): error -6
Please append a correct "root=" boot option; here are the available partitions:
0100            4096 ram0 (driver?)
0101            4096 ram1 (driver?)
0102            4096 ram2 (driver?)
0103            4096 ram3 (driver?)
0104            4096 ram4 (driver?)
0105            4096 ram5 (driver?)
0106            4096 ram6 (driver?)
0107            4096 ram7 (driver?)
0108            4096 ram8 (driver?)
0109            4096 ram9 (driver?)
010a            4096 ram10 (driver?)
010b            4096 ram11 (driver?)
010c            4096 ram12 (driver?)
010d            4096 ram13 (driver?)
010e            4096 ram14 (driver?)
010f            4096 ram15 (driver?)
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

Bisect points to commit b2ae75052a8c ("ide: Fix interface autodetection
in legacy IDE driver (trial #2)". Reverting that patch fixes the problem.

Bisect log is attached. A complete log is available at:

http://kerneltests.org/builders/qemu-x86-next/builds/557/steps/qemubuildcommand/logs/stdio

One does wonder if that patch fixes a problem, and qemu is wrong, or if it in
fact introduces a problem. It does appear a little odd, though, that such a
significant bug would remain undetected for 8+ years.

Guenter

---
# bad: [c84d0bbe09ea83f9c502ed08f585204e3d241344] Add linux-next specific files for 20170109
# good: [0c744ea4f77d72b3dcebb7a8f2684633ec79be88] Linux 4.10-rc2
git bisect start 'HEAD' 'v4.10-rc2'
# bad: [fde16c8250387573d869725a109eada33bc9675a] Merge remote-tracking branch 'net-next/master'
git bisect bad fde16c8250387573d869725a109eada33bc9675a
# bad: [edc498958581417ca07e8aa91b2822008fb78fc2] Merge remote-tracking branch 'clk/clk-next'
git bisect bad edc498958581417ca07e8aa91b2822008fb78fc2
# good: [92f93fc78e0a9f6d8b5485cbbf75950092d5c693] Merge remote-tracking branch 'arc-current/for-curr'
git bisect good 92f93fc78e0a9f6d8b5485cbbf75950092d5c693
# bad: [e7278bf07f430f347f7feac1ec5c2097d73e1091] Merge remote-tracking branch 'omap/for-next'
git bisect bad e7278bf07f430f347f7feac1ec5c2097d73e1091
# bad: [fdfc10327adbb19abe03d648850019d69a0be91a] Merge remote-tracking branch 'imx-mxs/for-next'
git bisect bad fdfc10327adbb19abe03d648850019d69a0be91a
# bad: [1d29523f70a991b69b305a4df8c48546ad73d01b] Merge remote-tracking branch 'drm-misc-fixes/for-linux-next-fixes'
git bisect bad 1d29523f70a991b69b305a4df8c48546ad73d01b
# good: [0b3d950354ca680ac42b2c92a4f4cc95870c11d5] Merge remote-tracking branch 'wireless-drivers/master'
git bisect good 0b3d950354ca680ac42b2c92a4f4cc95870c11d5
# good: [baf9cdf2dce8f4e01245aba80826a9e103565ddf] Merge remote-tracking branch 'input-current/for-linus'
git bisect good baf9cdf2dce8f4e01245aba80826a9e103565ddf
# good: [7738789fba09108a28a5fb4739595d9a0a2f85fe] selftests: x86/pkeys: fix spelling mistake: "itertation" -> "iteration"
git bisect good 7738789fba09108a28a5fb4739595d9a0a2f85fe
# bad: [d532005cf02ed6204f75fd368a2c4bc4cbdee655] Merge remote-tracking branch 'ide/master'
git bisect bad d532005cf02ed6204f75fd368a2c4bc4cbdee655
# good: [4730700af114c441369557e3fdc761a9f5acaa87] Merge remote-tracking branch 'crypto-current/master'
git bisect good 4730700af114c441369557e3fdc761a9f5acaa87
# bad: [b2ae75052a8c1611b2030fa49ba1c6b6439fa04f] ide: Fix interface autodetection in legacy IDE driver (trial #2)
git bisect bad b2ae75052a8c1611b2030fa49ba1c6b6439fa04f
# first bad commit: [b2ae75052a8c1611b2030fa49ba1c6b6439fa04f] ide: Fix interface autodetection in legacy IDE driver (trial #2)