Re: [Xen-devel] pte query?

[Jacob Gorm Hansen <jacobg@xxxxxxx>]

On 11/15/05, Aaron J. Marks <ajmarks@xxxxxxxxxxxxxx> wrote:
> hi,
>
> what's the best way (if at all) to iterate through all of a domain's page
> tables within xen 2.0.6? i need to find all references to a specific pte
> value (which is a given). essentially, a reverse page-table lookup.

This is not something you wish to do in a production system, though I
can imagine situations where this would be useful for debugging.

Basically, you will have to instrument Xen with a n-level nested loop,
that does something like (show here for 2-level x86-32 ptes):

unsigned long* pgd = map_domain_page(d->arch.mm->pgd)
for(i=0; i<HYPERVISOR_VIRT_START>>22; i++)
{
 if( pgd[i] & _PAGE_PRESENT) {
  unsigned long* ptes = map_domain_page( pgd[i]>>12);
  for(j=0; j<1024; j++) {
   if( ptes[j] & _PAGE_PRESENT && ptes[j]>>12==my_mfn) {
    printk("found it!\n");
   }
   unmap_domain_page(ptes);
  }
 }

Good luck,
Jacob

--
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