|
On 15/11/15 00:14, Atom2 wrote:
Right - it would appear that the USE flag is definitely not what
you wanted, and causes bad compilation for Xen. The do_IRQ
disassembly you sent is a the result of disassembling a whole
block of zeroes. Sorry for leading you on a goose chase - the
double faults will be the product of bad compilation, rather
than anything to do with your specific problem.
Hi Andrew,
there's absolutely no need to appologize as it is me who asked for
help and you who generously stepped in and provided it. I really
do appreciate your help and it is for me, as the one seeking help,
to provide all the information you deem necessary and you ask for.
However, the final log you sent (dmesg) is using a debug Xen,
which is what I was attempting to get you to do originally.
Next time I know better how to arrive at a debug XEN. It's all
about learning.
We
still observe that the VM ends up in 32bit non-paged mode but
with an RIP with bit 32 set, which is an invalid state to be
in. However, there was nothing particularly interesting in the
extra log information.
Please can you rerun with "hvm_debug=0xc3f", which will cause
far more logging to occur to the console while the HVM guest is
running. That might show some hints.
I haven't done that yet - but please see my next paragraph. If you
are still interested in this, for whatever reason, I am clearly
more than happy to rerun with your suggested option and provide
that information as well.
Also, the fact that this occurs just after starting SeaBIOS is
interesting. As you have switched versions of Xen, you have
also switched hvmloader, which contains the SeaBIOS binary
embedded in it. Would you be able to compile both 4.5.1 and
4.5.2 and switch the hvmloader binaries in use. It would be
very interesting to see whether the failure is caused by the
hvmloader binary or the hypervisor. (With `xl`, you can use
firmware_override="/full/path/to/firmware" to override the
default hvmloader).
Your analysis was absolutely spot on. After re-thinking this for a
moment, I thought going down that route first would make a lot of
sense as PV guests still do work and one of the differences to HVM
domUs is that the former do _not_ require SeaBIOS. Looking at my
log files of installed packages confirmed an upgrade from SeaBIOS
1.7.5 to 1.8.2 in the relevant timeframe which obviously had not
made it to the hvmloader of xen-4.5.1 as I did not re-compile xen
after the upgrade of SeaBIOS.
So I re-compiled xen-4.5.1 (obviously now using the installed
SeaBIOS 1.8.2) and the same error as with xen-4.5.2 popped up -
and that seemed to strongly indicate that there indeed might be an
issue with SeaBIOS as this probably was the only variable that had
changed from the original install of xen-4.5.1.
My next step was to downgrade SeaBIOS to 1.7.5 and to re-compile
xen-4.5.1. Voila, the system was again up and running. While still
having SeaBIOS 1.7.5 installed, I also re-compiled xen-4.5.2 and
... you probably guessed it ... the problem was gone: The system
boots up with no issues and everything is fine again.
So in a nutshell: There seems to be a problem with SeaBIOS 1.8.2
preventing HVM doamins from successfully starting up. I don't know
what this is triggered from, if this is specific to my hardware or
whether something else in my environment is to blame.
In any case, I am again more than happy to provide data / run a
few tests should you wish to get to the grounds of this.
I do owe you a beer (or any other drink) should you ever be at my
location (i.e. Vienna, Austria).
Many thanks again for your analysis and your first class support.
Xen and their people absolutely rock!
Great - so confirms the issue as a SeaBIOS interaction issue, rather
than a hypervisor regression.
As I said before, I am still certain that a guest should not be able
to get itself into the crashing state (short of a hardware errata),
so I still suspect that there is a latent hypervisor emulation bug
which has been tickled by the SeaBIOS update.
Would you please mind running the bad HVMLoader on Xen 4.5.2 with
hvm_debug=0xc3f ? I am still hoping that that will shed some light
on SeaBIOS actions just leading up to the crash.
Are you able to experiment with newer versions of Xen? It would be
interesting to see whether the issue is still present in Xen 4.6
~Andrew
|
