Major KVM issues with kernel 4.5 on the host

[Marc Haber]

Hi,

I have a (semi-productive[1]) system ("host") running Debian unstable.
On this system, a few VMs (Debian unstable, Debian testing) ("vm1",
"vm2", "vm3") are running. I roll my own kernels and take vanilla
upstream sources. No distribution patches.

Since host was updated to Kernel 4.5, the VMs have started acting up.
All of them. The range of strangeness begins with "relocation error,
system halted" on system startup, corrupted data files on disk,
filesystems remounted read-only, libraries rejected with "invalid ELF
format", binaries segfaulting all of a sudden. Downgrading host to
kernel 4.4.5 magically fixed all those issues.

Going back to 4.5 lets the issues reappear. Here, for example, ext4 fs
errors, logged in one of the VMs:

Mar 17 17:39:57 spinturn kernel: EXT4-fs error (device dm-0): ext4_lookup:1602: inode #415065: comm aide: deleted inode referenced: 546538
Mar 17 17:39:57 spinturn kernel: EXT4-fs error (device dm-0): ext4_lookup:1602: inode #415065: comm aide: deleted inode referenced: 546530
Mar 17 17:39:57 spinturn kernel: EXT4-fs error (device dm-0): ext4_iget:4269: inode #546543: comm aide: bad extra_isize (44800 != 256)
Mar 17 17:39:58 spinturn kernel: EXT4-fs error (device dm-0): ext4_iget:4466: inode #546568: comm aide: bogus i_mode (144)
Mar 17 17:39:58 spinturn kernel: EXT4-fs error (device dm-0): ext4_lookup:1602: inode #546548: comm aide: deleted inode referenced: 546564
Mar 17 17:39:58 spinturn kernel: EXT4-fs error (device dm-0): ext4_lookup:1602: inode #546548: comm aide: deleted inode referenced: 546562
Mar 17 17:39:58 spinturn kernel: EXT4-fs error (device dm-0): ext4_iget:4269: inode #546563: comm aide: bad extra_isize (6464 != 256)
Mar 17 17:39:58 spinturn kernel: EXT4-fs error (device dm-0): ext4_iget:4466: inode #546561: comm aide: bogus i_mode (0)
Mar 17 17:39:58 spinturn kernel: EXT4-fs error (device dm-0): ext4_iget:4269: inode #546529: comm aide: bad extra_isize (1152 != 256)
Mar 17 17:39:58 spinturn kernel: EXT4-fs error (device dm-0): ext4_xattr_block_get:297: inode #546359: comm aide: bad block 677784

I'm going to try reproducing the issue on a less "important" machine
so that bisecting is less painful, but maybe you guys have an idea
what's going wrong here.

jftr, kernel 4.5 in guest and in standalone systems seems to be
unproblematic.

Greetings
Marc


[1] my main workstation, running enough services for the local network
that disturbances in its operation cause reasonable discomfort, but not the
Enterprise kind of "productive"

-- 
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Marc Haber         | "I don't trust Computers. They | Mailadresse im Header
Leimen, Germany    |  lose things."    Winona Ryder | Fon: *49 6224 1600402
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