Re: [dpdk-dev] [PATCH] eal/bsd: don't zero the pages during mmap in contigmem

[Tiwei Bie <tiwei.bie@intel.com>]

On Mon, May 08, 2017 at 09:53:57AM +0100, Bruce Richardson wrote:
> On Mon, May 08, 2017 at 08:09:16AM +0000, Tiwei Bie wrote:
> > Don't zero the pages during mmap in contigmem. Instead, zero the
> > pages after mmap in primary process. Otherwise, the multi-process
> > support will be broken, as the pages will be zeroed when secondary
> > processes map the memory.
> > 
> > Fixes: 82f931805506 ("contigmem: zero all pages during mmap")
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> > ---
> I agree there is a problem here, but I'm not sure about the solution to
> it. I still think that the kernel should zero the pages before they get
> given to userspace. Is there any way to keep that working e.g
> 
> * have them zeroed on mmap only when they are not already mmaped into
>   another process?
> * have them zeroed on init, and again on unmap by the last process to
>   have them mapped?
> 

I think it's the simplest way to fix it in userspace, so I just did it.
I'd like to fix it in kernel if you also prefer this.

Best regards,
Tiwei Bie