Re: [Xen-devel] Regression: qemu crash of hvm domUs with spice (backtrace included)

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 21 Apr 2015, Fabio Fantoni wrote:
> Il 21/04/2015 12:49, Stefano Stabellini ha scritto:
> > On Mon, 20 Apr 2015, Fabio Fantoni wrote:
> > > I updated xen and qemu from xen 4.5.0 with its upstream qemu included to
> > > xen
> > > 4.5.1-pre with qemu upstream from stable-4.5 (changed Config.mk to use
> > > revision "master").
> > > After few minutes I booted windows 7 64 bit domU qemu crash, tried 2 times
> > > with same result.
> > > 
> > > In the domU's qemu log:
> > > > qemu-system-i386: malloc.c:3096: sYSMALLOc: Assertion `(old_top ==
> > > > (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) -
> > > > __builtin_offsetof
> > > > (struct malloc_chunk, fd)))) && old_size == 0) || ((unsigned long)
> > > > (old_size) >= (unsigned long)((((__builtin_offsetof (struct
> > > > malloc_chunk,
> > > > fd_nextsize))+((2 * (sizeof(size_t))) - 1)) & ~((2 * (sizeof(size_t))) -
> > > > 1))) && ((old_top)->size & 0x1) && ((unsigned long)old_end & pagemask)
> > > > ==
> > > > 0)' failed.
> > > > Killing all inferiors
> > > In attachment the full backtrace of qemu crash.
> > > 
> > > With a fast search after I saw the backtrace I found a probable cause of
> > > regression (I'm not sure):
> > > http://xenbits.xen.org/gitweb/?p=staging/qemu-upstream-4.5-testing.git;a=commit;h=5c3402816aaddb15156c69df73c54abe4e1c76aa
> > > spice: make sure we don't overflow ssd->buf
> > > 
> > > Added also qemu-devel and spice-devel as cc.
> > > 
> > > If you need more informations/tests tell me and I'll post them.
> >   Maybe you could try to revert the offending commit
> > (5c3402816aaddb15156c69df73c54abe4e1c76aa)? Or even better bisect the
> > crash?
> Thanks for your reply.
> 
> I reverted to 4.5.0 on dom0 for now on that system because I'm busy trying to
> found another problem that cause very bad performance without errors or
> nothing in logs :( I don't know if if xen related, kernel related or other for
> now.
> 
> About this regression with spice I'll do further tests in next days (probably
> starting reverting the spice patch in qemu) but any help is appreciated.
> Based on data I have for now is possible that the problem is that qemu try to
> allocate other ram or videoram after domU create but with xen is not possible?
> In the spice related patch I saw something about dynamic allocation for
> example.

It is probably caused by a commit in the range:

1ebb75b1fee779621b63e84fefa7b07354c43a99..0b8fb1ec3d666d1eb8bbff56c76c5e6daa2789e4

there are only 10 commits in that range. By using git bisect you should
be able to narrow it down in just 3 tests.

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