RE: [PATCH 04/10] xen/arm: static memory initialization

[Penny Zheng <Penny.Zheng@xxxxxxx>]

Hi Jan

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Tuesday, May 18, 2021 3:16 PM
> To: Penny Zheng <Penny.Zheng@xxxxxxx>
> Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>; Wei Chen
> <Wei.Chen@xxxxxxx>; nd <nd@xxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx;
> sstabellini@xxxxxxxxxx; julien@xxxxxxx
> Subject: Re: [PATCH 04/10] xen/arm: static memory initialization
> 
> On 18.05.2021 07:21, Penny Zheng wrote:
> > This patch introduces static memory initialization, during system RAM boot
> up.
> >
> > New func init_staticmem_pages is the equivalent of init_heap_pages,
> > responsible for static memory initialization.
> >
> > Helper func free_staticmem_pages is the equivalent of free_heap_pages,
> > to free nr_pfns pages of static memory.
> > For each page, it includes the following steps:
> > 1. change page state from in-use(also initialization state) to free
> > state and grant PGC_reserved.
> > 2. set its owner NULL and make sure this page is not a guest frame any
> > more
> 
> But isn't the goal (as per the previous patch) to associate such pages with a
> _specific_ domain?
> 

Free_staticmem_pages are alike free_heap_pages, are not used only for 
initialization.
Freeing used pages to unused are also included.
Here, setting its owner NULL is to set owner in used field NULL.
Still, I need to add more explanation here.

> > --- a/xen/common/page_alloc.c
> > +++ b/xen/common/page_alloc.c
> > @@ -150,6 +150,9 @@
> >  #define p2m_pod_offline_or_broken_hit(pg) 0  #define
> > p2m_pod_offline_or_broken_replace(pg) BUG_ON(pg != NULL)  #endif
> > +#ifdef CONFIG_ARM_64
> > +#include <asm/setup.h>
> > +#endif
> 
> Whatever it is that's needed from this header suggests the code won't build
> for other architectures. I think init_staticmem_pages() in its current shape
> shouldn't live in this (common) file.
> 

Yes, I should include them all both under one specific config, maybe like
CONFIG_STATIC_MEM, and this config is arm-specific.

> > @@ -1512,6 +1515,49 @@ static void free_heap_pages(
> >      spin_unlock(&heap_lock);
> >  }
> >
> > +/* Equivalent of free_heap_pages to free nr_pfns pages of static
> > +memory. */ static void free_staticmem_pages(struct page_info *pg,
> unsigned long nr_pfns,
> > +                                 bool need_scrub)
> 
> Right now this function gets called only from an __init one. Unless it is
> intended to gain further callers, it should be marked __init itself then.
> Otherwise it should be made sure that other architectures don't include this
> (dead there) code.
> 

Sure, I'll add __init. Thx.

> > +{
> > +    mfn_t mfn = page_to_mfn(pg);
> > +    int i;
> 
> This type doesn't fit nr_pfns'es.
> 

Sure, nr_mfns is better in also many other places.

> Jan