Steven Rostedt wrote:
> Looking into the code in linux-2.6-xen-sparse/arch/i386/mm/ioremap-xen.c
> 
> I found some logic that did not make sense.  We have a loop than updates 
> the page tables in __direct_remap_pfn_range, and in the beginning of 
> that loop, there is a test that if we finished the page
> (v-u == PAGE_SIZE/sizeof(mmu_update_t)) we call the hypervisor to do our 
> update.  This is all fine and dandy but, but the code right after the 
> loop seems to be wrong.
> 
> There is a check if (v != u) then do some more work.  I'm assuming that 
> this code is there in case we didn't reach the if statement at the top 
> of the loop.  But what is wrong is that this check is invalid.  Although 
> the loop if statement sets v = u, the following if statement ignores the 
> fact that v++ is done at the bottom of the loop.  So if we really want 
> to do this extra work if we didn't finish the loop, then the test really 
> needs to be.
> 
> if ((v - u) != 1) { .... }
> 
> 
> Unless I'm missing something here, I've attached a patch.
>

I did miss something.  The fact that the loop may only go once.  This 
means that v - u will equal 1 and we miss that allocation.  So to handle 
  this, I'm submitting this patch that just keeps track of whether or 
not we need to do the final fixup.

-- Steve

Signed-off-by: Steven Rostedt <srostedt@redhat.com>