Re: [Xen-devel] [PATCH 2 of 4] x86: Introduce "top_of_mem"

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.03.12 at 15:42, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> It is very useful for the crashdump kernel to have an idea of what Xen
> thought was the maximum memory address was, especially if the
> crashdump kernel is 32bit.

But then you also need to update the value upon memory hotplug.
(And I assume subsequent patches will actually make use of this.)

Jan

> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
> diff -r 977fa1c61b3e -r 1e79fb200722 xen/arch/x86/mm.c
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -149,6 +149,7 @@ struct domain *dom_xen, *dom_io, *dom_co
>  /* Frame table size in pages. */
>  unsigned long max_page;
>  unsigned long total_pages;
> +u64 top_of_mem;
>  
>  unsigned long __read_mostly pdx_group_valid[BITS_TO_LONGS(
>      (FRAMETABLE_SIZE / sizeof(*frame_table) + PDX_GROUP_COUNT - 1)
> diff -r 977fa1c61b3e -r 1e79fb200722 xen/arch/x86/setup.c
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -1111,6 +1111,7 @@ void __init __start_xen(unsigned long mb
>             nr_pages >> (20 - PAGE_SHIFT),
>             nr_pages << (PAGE_SHIFT - 10));
>      total_pages = nr_pages;
> +    top_of_mem = e820.map[e820.nr_map-1].addr + e820.map[e820.nr_map-1].size;
>  
>      /* Sanity check for unwanted bloat of certain hypercall structures. */
>      BUILD_BUG_ON(sizeof(((struct xen_platform_op *)0)->u) !=
> diff -r 977fa1c61b3e -r 1e79fb200722 xen/include/asm-x86/mm.h
> --- a/xen/include/asm-x86/mm.h
> +++ b/xen/include/asm-x86/mm.h
> @@ -296,6 +296,7 @@ int get_superpage(unsigned long mfn, str
>  #endif
>  extern unsigned long max_page;
>  extern unsigned long total_pages;
> +extern u64 top_of_mem;
>  void init_frametable(void);
>  
>  #define PDX_GROUP_COUNT ((1 << L2_PAGETABLE_SHIFT) / \
> 
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