Re: [Xen-devel] [BUG] XEN 4.3.3 - segfault in xl create for HVM with PCI passthrough

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-11-05 at 13:01 +0100, Atom2 wrote:

Thanks for all that, sadly it's not giving me any clues what is going
wrong :-/

> To me, it looks as if something is broken with the PCI passthrough stuff 
> and that has started with 4.3.3. Strangely however, valgrind seems to 
> work around that issue insofar that no segfault happens. Is there any 
> explanation of the different behaviour between native execution of xl 
> and starting xl under valgrind's control?

Valgrind has it's own memory allocator etc, but it's supposed to catch
errors, not hide them. I think even 3.10.0 is missing support for some
hypercalls which are being used by passthrough, which is why we are
continuing to see different behaviours.

I think we are reaching the point of diminishing returns with vagrind.
It probably is worth rerunning with "-v --leak-check=full", but after
that we'd be looking at adding valgrind patches for the new hypercalls,
which I don't think will be worthwhile (although I intend to write the
patches anyway).

So unless "-v --leak-check=full" tells me something (which I'm doubtful
of at this stage) I think we're back to bisecting the changes since
4.3.1, sorry.

Ian.


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