RE: [PATCH 2/2] xen/arm: Handle reserved heap pages in boot and heap allocator

[Henry Wang <Henry.Wang@xxxxxxx>]

Hi Stefano,

> -----Original Message-----
> From: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> > > But also it looks like that on arm32 we have specific requirements for
> > > Xen heap:
> > >
> > >      *  - must be 32 MiB aligned
> > >      *  - must not include Xen itself or the boot modules
> > >      *  - must be at most 1GB or 1/32 the total RAM in the system if less
> > >      *  - must be at least 32M
> >
> > ...here, with the "1/32 the total RAM" now being "1/32 of the total reserved
> > heap region", since heap_pages is now reserved_heap_pages.
> 
> I see. I didn't realize the full implications of the memory being used
> for both xenheap and domheap on arm32. In that case, I would simply do
> the following:
> 
> 
>     heap_pages = !reserved_heap ? ram_pages : reserved_heap_pages;
> 
>     if ( opt_xenheap_megabytes )
>         xenheap_pages = opt_xenheap_megabytes << (20-PAGE_SHIFT);
>     else
>     {
>         xenheap_pages = (heap_pages/32 + 0x1fffUL) & ~0x1fffUL;
>         xenheap_pages = max(xenheap_pages, 32UL<<(20-PAGE_SHIFT));
>         xenheap_pages = min(xenheap_pages, 1UL<<(30-PAGE_SHIFT));
>     }
> 
>     if ( reserved_heap )
>         e = reserved_heap_end;
>     else
>     {
>         do
>         {
>             e = consider_modules(ram_start, ram_end,
>                                  pfn_to_paddr(xenheap_pages),
>                                  32<<20, 0);
> 
>             if ( e )
>                 break;
> 
>             xenheap_pages >>= 1;
>         } while ( !opt_xenheap_megabytes && xenheap_pages > 32<<(20-
> PAGE_SHIFT) );
>     }
> 
>     if ( ! e ||
>          ( reserved_heap && reserved_heap_pages < 32<<(20-PAGE_SHIFT) ) )
>         panic("Not enough space for xenheap\n");
> 
>     domheap_pages = heap_pages - xenheap_pages;

Thanks very much for your time and patience. I will follow this way - with
the comment also updated of course (I didn't realize the comment needs to
be changed until yesterday when I sent the reply to your last comment.)

Kind regards,
Henry