RE: [Xen-devel] Unknown interrupt on x86_64 Xen on ES7000 x86_64

["Nakajima, Jun" <jun.nakajima@xxxxxxxxx>]

Puthiyaparambil, Aravindh wrote:
>>> It looks like the page fault/interrupt is happening in map_alloc().
>>> I see that alloc_heap_pages() and map_alloc() are called before
>>> without any issues. Not sure why it is tripping up now. Any ideas?
>> 
>> Not really. Perhaps some part of the bitmap is not properly mapped? I
>> think you'll have to add a bunch more tracing -- find out what
>> address is actually faulting and work backwards to see why it's not
>> mapped. If it looks like it should be valid then maybe look at the
>> code that is intended to 1:1 map all RAM, in
>> arch/x86/setup.c:__start_xen() (the code is wrapped in
>> CONFIG_x86_64). 
> 
> I found out that the "Unknown Interrupt" issue happens only when debug
> is turned on in Xen (verbose & debug=y in Rules.mk). When debug is
> turned off the systems dies in the middle of "Scrubbing Free RAM". I
> have attached a serial output of the boot messages
> (es7000_x86_64_nodebug_6065.txt). This could be Bugzilla #147.
> Should I be still trying to find the faulting address in the debug
> case? 
> 
I have the same problem "Unknown Interrupt" on a DP machine. Looks like
#PF is happening at => when xen is built with debug=y.

static void map_alloc(unsigned long first_page, unsigned long nr_pages)
{
    ...
    curr_idx  = first_page / PAGES_PER_MAPWORD;
    start_off = first_page & (PAGES_PER_MAPWORD-1);
    end_idx   = (first_page + nr_pages) / PAGES_PER_MAPWORD;
    end_off   = (first_page + nr_pages) & (PAGES_PER_MAPWORD-1);

    if ( curr_idx == end_idx )
    {
        alloc_bitmap[curr_idx] &= -(1UL<<end_off) |
((1UL<<start_off)-1);
    }
    else
    {
        alloc_bitmap[curr_idx] &= (1UL<<start_off)-1;
        while ( ++curr_idx != end_idx ) alloc_bitmap[curr_idx] = 0;
 =>       alloc_bitmap[curr_idx] &= -(1UL<<end_off);
    }
}

If I change 
        while ( ++curr_idx != end_idx - 1 ) alloc_bitmap[curr_idx] = 0;
I can work around it.

Jun
---
Intel Open Source Technology Center

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