Subject: Re: [PATCH 5/5] [PPC] provide walk_memory_resource() for ppc

From: Badari Pulavarty <[email-masked]>
Date: Tue, 13 May 2008 08:09:25 -0700

On Mon, 2008-05-12 at 17:17 -0700, Geoff Levand wrote:
> Hi,
> 
> I've had some trouble with this change.
> 
> Badari Pulavarty wrote:
> > Provide walk_memory_resource() for ppc64. PPC maintains 
> > logic memory region mapping in lmb.memory structures. Walk
> > through these structures and do the callbacks for the
> > contiguous chunks.
> 
> ...
> 
> > --- linux-2.6.25-rc3.orig/arch/powerpc/mm/mem.c	2008-03-05 10:14:28.000000000 -0800
> > +++ linux-2.6.25-rc3/arch/powerpc/mm/mem.c	2008-03-05 10:32:16.000000000 -0800
> > @@ -148,19 +148,35 @@ out:
> >  
> >  /*
> >   * walk_memory_resource() needs to make sure there is no holes in a given
> > - * memory range. On PPC64, since this range comes from /sysfs, the range
> > - * is guaranteed to be valid, non-overlapping and can not contain any
> > - * holes. By the time we get here (memory add or remove), /proc/device-tree
> > - * is updated and correct. Only reason we need to check against device-tree
> > - * would be if we allow user-land to specify a memory range through a
> > - * system call/ioctl etc. instead of doing offline/online through /sysfs.
> > + * memory range. PPC64 does not maintain the memory layout in /proc/iomem.
> > + * Instead it maintains it in lmb.memory structures. Walk through the
> > + * memory regions, find holes and callback for contiguous regions.
> >   */
> >  int
> >  walk_memory_resource(unsigned long start_pfn, unsigned long nr_pages, void *arg,
> >  			int (*func)(unsigned long, unsigned long, void *))
> >  {
> > -	return  (*func)(start_pfn, nr_pages, arg);
> > +	struct lmb_property res;
> > +	unsigned long pfn, len;
> > +	u64 end;
> > +	int ret = -1;
> > +
> > +	res.base = (u64) start_pfn << PAGE_SHIFT;
> > +	res.size = (u64) nr_pages << PAGE_SHIFT;
> > +
> > +	end = res.base + res.size - 1;
> > +	while ((res.base < end) && (lmb_find(&res) >= 0)) {
>                                     ^^^^^^^^^^^^^^
> 
> In the PS3 platform code (arch/pwerpc/platfroms/ps3/mm.c) the hotplug
> memory is added like this:
> 
> 	...
> 	result = add_memory(0, start_addr, map.r1.size);
> 	...
> 	result = online_pages(start_pfn, nr_pages);
> 	...
> 
> In its work, online_pages() eventually calls walk_memory_resource(),
> which has been changed as above to do a test on lmb_find(). I found
> that this lmb_find() test always fails for PS3 since add_memory()
> does not call lmb_add().
> 
> Is it the responsibility of the platform code to call lmb_add(), or
> should that be done by add_memory()?

Since "lmb" code is specific to architecture, I would prefer that
arch specific code is responsible for manipulating "lmb"s instead of
generic code.

In case of ppc64, I added lmb_add() call in /proc/device-tree
manipulation code. Are there any arch specific calls for PS3
when add/remove memory happens ? If there are no other calls,
you can do lmb_add() in ps3_mm_add_memory(). For remove, we
need to find a better place.

Thanks,
Badari