Re: [Xen-devel] Xen 4.8.0 dom0pvh=1 causes ext4 filesystem corruption

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 10/03/2017 00:09, Steven Haigh wrote:
> On 10/03/17 02:13, Valtteri Kiviniemi wrote:
>> Hi,
>>
>> Yesterday I decided to upgrade my Xen version from 4.6.0 to 4.8.0. I
>> compiled it from source and at the same time I compiled the latest Linux
>> kernel (4.10.1).
>>
>> When rebooting I decided to try if dom0 PVH would work (with previous
>> Xen version it just caused kernel panic). Seemed to boot fine until
>> systemd started mounting the root filesystem and then the console was
>> filled with ext4 errors. Couldn't even log in.
>>
>> Booting with a systemrescuecd and running fsck just caused the whole
>> filesystem to be re-attached in thousands of small pieces under
>> lost+found. I was sure that this was a some kind of hardware failure, so
>> I switched my hard drives and did a clean reinstall for dom0 and tried
>> again. Again, after a reboot the whole rootfs was completely corrupted.
>>
>> Second reinstall and this time I disabled dom0 PVH and the system booted
>> just fine, and no ext4 errors. My root filesystem is just a simple Linux
>> software raid1 with ext4 on top of it.
>>
>> Now that I started thinking I have also had strange ext4 errors
>> happening inside my guests, so I also disabled PVH from all the guests.
>> With guests the ext4 error is always the same: "EXT4-fs error (device
>> xvda1): ext4_iget:4665: inode #317: comm find: bogus i_mode (135206)"
>>
>> Unfortunately I don't have any logs from the dom0 corruption as I can't
>> even log in to the system when dom0 PVH is enabled. The corruption
>> happens instantly during system bootup.
> I have this happen a lot using pvh mode in previous Xen versions. Is it
> supposed to be 'working' yet or is it still not recommended for use?

That version of PVH has just been ripped out of Linux, and is in the
process of being ripped out of the hypervisor.

The replacement, accessed by using dom0=pvh is available in master, will
be present in Xen 4.9, and should work with Linux 4.11 and FreeBSD
Current.  (Roger, Boris - please correct me if I am wrong.)

The same Linux and FreeBSD versions should function perfectly well as
plain domUs in PVH mode, by selecting device_model=none in the domain
configuration.  (Dom0 is rather more complicated than domU, due to the
shared responsibility of real hardware with Xen.)

~Andrew

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