Re: [Xen-devel] [PATCH] x86: consider modules when cutting off memory

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.11.13 at 12:32, Keir Fraser <keir.xen@xxxxxxxxx> wrote:
> On 18/11/2013 00:37, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
>> The code in question runs after module ranges got already removed from
>> the E820 table, so when determining the new maximum page/PDX we need to
>> explicitly take them into account.
>> 
>> Furthermore we need to round up the ending addresses here, in order to
>> fully cover eventual partial trailing pages.
> 
> Is rounding up the right thing to do? We round down in find_max_pfn()?

Yes, it is - we're trying to determine a new max_page/max_pdx
here, so we should include the trailing part of a partial page. This
is particularly necessary for the modules, as otherwise the last
few bytes of a module may end up being in memory not satisfying
mfn_valid().

If anything, we'd need to round down after the E820 loop, and
round up after the modules one. But I don't think the two max_p*
being one too big here would matter much, so uniformly rounding
up seems sufficient.

Jan

>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> 
>> --- a/xen/arch/x86/setup.c
>> +++ b/xen/arch/x86/setup.c
>> @@ -1013,9 +1013,17 @@ void __init __start_xen(unsigned long mb
>>                      ASSERT(j);
>>                  }
>>                  map_e = boot_e820.map[j].addr + boot_e820.map[j].size;
>> -                if ( (map_e >> PAGE_SHIFT) < max_page )
>> +                for ( j = 0; j < mbi->mods_count; ++j )
>>                  {
>> -                    max_page = map_e >> PAGE_SHIFT;
>> +                    uint64_t end = pfn_to_paddr(mod[j].mod_start) +
>> +                                   mod[j].mod_end;
>> +
>> +                    if ( map_e < end )
>> +                        map_e = end;
>> +                }
>> +                if ( PFN_UP(map_e) < max_page )
>> +                {
>> +                    max_page = PFN_UP(map_e);
>>                      max_pdx = pfn_to_pdx(max_page - 1) + 1;
>>                  }
>>                  printk(XENLOG_WARNING "Ignoring inaccessible memory range"
>> 
>> 
>> 




_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel