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

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 09/03/12 15:43, Jan Beulich wrote:
>>>> On 09.03.12 at 15:42, Andrew Cooper <andrew.cooper3@citrix.com> 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

Where/how does memory hotplug get exposed then?  A cursory look in mm.c
has references to hotplug in the init paths.

A subsequent patch does make use of this value.

~Andrew

>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>>
>> 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) / \
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@lists.xen.org 
>> http://lists.xen.org/xen-devel 
>
>

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com