Re: [Xen-devel] arch_init_memory() change

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

Actually, whether that fix works or not, I'm inclined to agree that just
fixing this particular e820 iterator is the better way to go.

 -- Keir

On 23/6/07 16:18, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx> wrote:

> The code in arch/x86/setup.c with comment "Ensure all E820 RAM regions are
> page-aligned and -sized" is supposed to fix this. In this case it should
> turn the E820 entry into a zero-sized entry that is then discarded when the
> e820 map is sanitized. Are you running a version of Xen that's missing this
> code?
> 
>  -- Keir
> 
> On 22/6/07 17:28, "Altobelli, David" <david.altobelli@xxxxxx> wrote:
> 
>> In xen/arch/x86/mm.c, arch_init_memory() does not follow the same logic
>> as find_max_pfn().  If a 4k non page aligned E820_RAM entry exists as
>> the last RAM entry in the e820 map, it will be skipped by
>> find_max_pfn(), but not by arch_init_memory(), triggering BUG_ON(pfn !=
>> max_page).
>> 
>> The logic in arch_init_memory() could be changed to mirror
>> find_max_pfn():
>> --- xen/arch/x86/mm.c.orig      2007-06-22 10:10:19.000000000 -0500
>> +++ xen/arch/x86/mm.c   2007-06-22 10:11:39.000000000 -0500
>> @@ -220,6 +220,8 @@ void arch_init_memory(void)
>>          /* Every page from cursor to start of next RAM region is I/O.
>> */
>>          rstart_pfn = PFN_UP(e820.map[i].addr);
>>          rend_pfn   = PFN_DOWN(e820.map[i].addr + e820.map[i].size);
>> +        if (rstart_pfn >= rend_pfn)
>> +            continue;
>>          for ( ; pfn < rstart_pfn; pfn++ )
>>          {
>>              BUG_ON(!mfn_valid(pfn));
>> 
>> But I think this breaks the sharing logic.  It might be better to just
>> remove the BUG_ON():
>> --- xen/arch/x86/mm.c.orig      2007-06-22 10:10:19.000000000 -0500
>> +++ xen/arch/x86/mm.c   2007-06-22 11:20:42.000000000 -0500
>> @@ -229,7 +229,6 @@ void arch_init_memory(void)
>>          /* Skip the RAM region. */
>>          pfn = rend_pfn;
>>      }
>> -    BUG_ON(pfn != max_page);
>> 
>>      subarch_init_memory();
>>  }
>> 
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxxxxxxxx
>> http://lists.xensource.com/xen-devel
> 
> 
> 
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