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[Xen-devel] Re: [PATCH 3/5] xen: allow balloon driver to use more than o

To: David Vrabel <david.vrabel@xxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH 3/5] xen: allow balloon driver to use more than one memory region
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Tue, 6 Sep 2011 17:57:06 -0400
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On Fri, Aug 19, 2011 at 03:57:18PM +0100, David Vrabel wrote:
> Allow the xen balloon driver to populate its list of extra pages from
> more than one region of memory.  This will allow platforms to provide
> (for example) a region of low memory and a region of high memory.
> 
> The maximum possible number of extra regions is 128 (== E820MAX) which
> is quite large so xen_extra_mem is placed in __initdata.  This is safe
> as both xen_memeory_setup() and balloon_init() are in __init.
              ^^^^^^ memory.

> 
> The balloon regions themselves are not altered (i.e., there is still
> only the one region).
> 
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> ---
>  arch/x86/xen/setup.c  |   20 +++++++++---------
>  drivers/xen/balloon.c |   51 ++++++++++++++++++++++++++++--------------------
>  include/xen/page.h    |    9 +++++++-
>  3 files changed, 48 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index c3b8d44..4720c2d 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -37,7 +37,7 @@ extern void xen_syscall_target(void);
>  extern void xen_syscall32_target(void);
>  
>  /* Amount of extra memory space we add to the e820 ranges */
> -phys_addr_t xen_extra_mem_start, xen_extra_mem_size;
> +struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
>  
>  /* 
>   * The maximum amount of extra memory compared to the base size.  The
> @@ -56,7 +56,7 @@ static void __init xen_add_extra_mem(unsigned long pages)
>       unsigned long pfn;
>  
>       u64 size = (u64)pages * PAGE_SIZE;
> -     u64 extra_start = xen_extra_mem_start + xen_extra_mem_size;
> +     u64 extra_start = xen_extra_mem[0].start + xen_extra_mem[0].size;
>  
>       if (!pages)
>               return;
> @@ -66,7 +66,7 @@ static void __init xen_add_extra_mem(unsigned long pages)
>  
>       memblock_x86_reserve_range(extra_start, extra_start + size, "XEN 
> EXTRA");
>  
> -     xen_extra_mem_size += size;
> +     xen_extra_mem[0].size += size;
>  
>       xen_max_p2m_pfn = PFN_DOWN(extra_start + size);
>  
> @@ -239,7 +239,7 @@ char * __init xen_memory_setup(void)
>  
>       memcpy(map_raw, map, sizeof(map));
>       e820.nr_map = 0;
> -     xen_extra_mem_start = mem_end;
> +     xen_extra_mem[0].start = mem_end;
>       for (i = 0; i < memmap.nr_entries; i++) {
>               unsigned long long end;
>  
> @@ -267,8 +267,8 @@ char * __init xen_memory_setup(void)
>                               e820_add_region(end, delta, E820_UNUSABLE);
>               }
>  
> -             if (map[i].size > 0 && end > xen_extra_mem_start)
> -                     xen_extra_mem_start = end;
> +             if (map[i].size > 0 && end > xen_extra_mem[0].start)
> +                     xen_extra_mem[0].start = end;
>  
>               /* Add region if any remains */
>               if (map[i].size > 0)
> @@ -276,10 +276,10 @@ char * __init xen_memory_setup(void)
>       }
>       /* Align the balloon area so that max_low_pfn does not get set
>        * to be at the _end_ of the PCI gap at the far end (fee01000).
> -      * Note that xen_extra_mem_start gets set in the loop above to be
> -      * past the last E820 region. */
> -     if (xen_initial_domain() && (xen_extra_mem_start < (1ULL<<32)))
> -             xen_extra_mem_start = (1ULL<<32);
> +      * Note that the start of balloon area gets set in the loop above
> +      * to be past the last E820 region. */
> +     if (xen_initial_domain() && (xen_extra_mem[0].start < (1ULL<<32)))
> +             xen_extra_mem[0].start = (1ULL<<32);
>  
>       /*
>        * In domU, the ISA region is normal, usable memory, but we
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 5814022..996cf65 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -555,11 +555,35 @@ void free_xenballooned_pages(int nr_pages, struct 
> page** pages)
>  }
>  EXPORT_SYMBOL(free_xenballooned_pages);
>  
> -static int __init balloon_init(void)
> +static void __init balloon_add_memory_region(unsigned long start_pfn, 
> unsigned long pages)

That looks suspiciously like it has more than 80 lines. You ran the
_all_ of the patches through scripts/checkpath.pl right?

>  {
> -     domid_t domid = DOMID_SELF;
>       unsigned long pfn, extra_pfn_end;
>       struct page *page;
> +
> +     /*
> +      * Initialise the balloon with excess memory space.  We need
> +      * to make sure we don't add memory which doesn't exist or
> +      * logically exist.  The E820 map can be trimmed to be smaller
> +      * than the amount of physical memory due to the mem= command
> +      * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
> +      * on a system with memory which requires highmem to access,
> +      * don't try to use it.


That whole comment is just confusing.. But I do know that you
just moved it, but I wonder if it makes sense to remove it or
alter it in the future.

> +      */
> +     extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
> +                         start_pfn + pages);
> +     for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
> +             page = pfn_to_page(pfn);
> +             /* totalram_pages and totalhigh_pages do not
> +                include the boot-time balloon extension, so
> +                don't subtract from it. */
> +             __balloon_append(page);
> +     }
> +}
> +
> +static int __init balloon_init(void)
> +{
> +     domid_t domid = DOMID_SELF;
> +     int i;
>       int ret;
>  
>       if (!xen_domain())
> @@ -588,25 +612,10 @@ static int __init balloon_init(void)
>       register_memory_notifier(&xen_memory_nb);
>  #endif
>  
> -     /*
> -      * Initialise the balloon with excess memory space.  We need
> -      * to make sure we don't add memory which doesn't exist or
> -      * logically exist.  The E820 map can be trimmed to be smaller
> -      * than the amount of physical memory due to the mem= command
> -      * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
> -      * on a system with memory which requires highmem to access,
> -      * don't try to use it.
> -      */
> -     extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
> -                         (unsigned long)PFN_DOWN(xen_extra_mem_start + 
> xen_extra_mem_size));
> -     for (pfn = PFN_UP(xen_extra_mem_start);
> -          pfn < extra_pfn_end;
> -          pfn++) {
> -             page = pfn_to_page(pfn);
> -             /* totalram_pages and totalhigh_pages do not include the 
> boot-time
> -                balloon extension, so don't subtract from it. */
> -             __balloon_append(page);
> -     }
> +     for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
> +             if (xen_extra_mem[i].size)
> +                     
> balloon_add_memory_region(PFN_UP(xen_extra_mem[i].start),
> +                                               
> PFN_DOWN(xen_extra_mem[i].size));
>  
>       return 0;
>  }
> diff --git a/include/xen/page.h b/include/xen/page.h
> index 0be36b9..b432c03 100644
> --- a/include/xen/page.h
> +++ b/include/xen/page.h
> @@ -3,6 +3,13 @@
>  
>  #include <asm/xen/page.h>
>  
> -extern phys_addr_t xen_extra_mem_start, xen_extra_mem_size;
> +struct xen_memory_region {
> +     phys_addr_t start;
> +     phys_addr_t size;
> +};
> +
> +#define XEN_EXTRA_MEM_MAX_REGIONS 128 /* == E820MAX */
> +
> +extern struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS];

__initdata

>  
>  #endif       /* _XEN_PAGE_H */
> -- 
> 1.7.2.5

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