Re: [Qemu-devel] [Bug 1156313] [NEW] X86-64 flags handling broken

[Torbjorn Granlund]

Richard Henderson <address@hidden> writes:

  Patch at http://patchwork.ozlabs.org/patch/229139/
  
Thanks.  I can confirm that this fixes the bug triggered by my test case
(and yours).  However, the instability of Debian GNU/Linux x86_64 has
not improved.

The exact same Debian version (debian "testing") updated at the same
time runs well on hardware.

My qemu Debian system now got messed up, since I attempted an upgrade in
the buggy qemu, which segfaulted several times during the upgrade.  I
need to reinstall, and then rely on -snapshot.

There is a problem with denorms which is reproducible, but whether that
is a qemu bug, and whether it can actually cause the observed
instability, is questionable.  Here is a testcase for that problem:

qemu-denorm-problem.s
Description: Binary data

It should terminate.  The observed buggy behaviour is that it hangs.

The instability problem can be observed at gmplib.org/devel/tm-date.html.
hwl-deb.gmplib.org is Debian under qemu with -cpu Haswell,+adx.

Not that the exact same qemu runs FreeBSD flawlessly (hwl.gmplib.org).
It is neither instable nor does it run the denorms testcase poorly.

I fully realise this is a hopeless bug report, but I am sure you can
reproduce it, since it is far from GMP specific.  After all apt-get
update; apt-get upgrade triggered it.  Debugging it will be a nightmare.

Qemu version: main git repo from less than a week ago + Richard ADX
patch.

-- 
Torbjörn