Re: [Xen-devel] [PATCH] xen/arm: add warning if memory modules overlap

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

Sorry for the late answer.

On 11/10/2019 20:07, Brian Woods wrote:
> On Fri, Oct 11, 2019 at 07:17:29PM +0100, Julien Grall wrote:
> > This code is also only called at boot where there are bigger time consuming
> > part (such as domheap initialization). So I would be surprised if you see
> > any improvement (other than a couple of cycles) in boot time here.
> >
> > Therefore, I would favor a readable solution over a micro-optimized solution
> > here.
> Which is why I wanted to put it where it was in the patch.  Where the
> user would see the warning after the information about the memory
> modules were printed (and fair early).
I had a think about it, dumping the modules informations before is useful if you 
know that you have one module max per kind. So you avoid to print the modules 
address/size in the warning.
However, it is possible to have multiple kernel module (as long as they don't 
have the same start address), you could end up with the following message:
"WARNING: modules Kernel and Kernel overlap"

To make the message more meaningful, we would need to print the modules 
address/size. Therefore, I don't view that it is important to check overlapping 
in early_print_info(). In this case I would favor any code that don't add a 
double for loop.
While thinking about this case, it made me realize that we only check the start 
address to consider a match. This means if the size is different, then it will 
be ignored. I think we ought to throw at least warning for this case as well.
Would you mind to have a look?

> Either way, take your pick of location and if it's only debug or not and
> I can write it up and test it.
I would still prefer in add_boot_module(). See why above.

Cheers,

--
Julien Grall

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