Re: [Qemu-devel] 2 MiB alignment in qemu_vmalloc()

[Alexander Graf]

On 12.10.2011, at 23:19, Stefan Weil wrote:

> Am 12.10.2011 22:47, schrieb Alexander Graf:
>> Well, yes, my point is that it's a bug in valgrind that should be fixed. I 
>> don't think we should special-case QEMU because of bugs in debugging 
>> software :)
>> 
>> Alex
> 
> Yes, the valgrind bug should be fixed. I don't know why it isn't,
> but that's not the point:
> 
> Valgrind is very valuable for finding certain kinds of bugs in QEMU
> which we want to find and fix (I hope we agree on this).
> Therefore developers should be able to use it.
> 
> Today, they cannot use Valgrind with QEMU out-of-the box,
> because they get an assertion. Some developers will stop here.
> Others will ask Google, look in Valgrind's code and spend some
> time to find and fix the problem before they start using
> Valgrind to find QEMU bugs.
> 
> They could have spent their time better.
> 
> I can try to make QEMU more useable with Valgrind by changing
> the QEMU code (which was Valgrind compatible up to Avi's change).
> 
> I cannot change the Valgrind code, and even if I could, it would
> take a lot of time until all Linux distributions would include a
> fixed Valgrind :-(
> 
> If all existing gdb versions did not work with QEMU,
> but there were a simple QEMU change which made them work,
> what would you do?

I would add a command line option to modify the alignment in runtime, 
defaulting it to something sane (16MB), so you can work around bugs in vagrind 
with a simple parameter :)


Alex