Fwd: about page table

[吴锐 <19890121wr@gmail.com>]

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Hi,everyone
I have been using dbg_pv_va2mfn() function to scan PV dom's page
table.However,when i intended to modify the page table's entry.Something
went wrong.
Should I modify the P2M and M2P table,either?But I kind of lose track of how
things work at P2M and M2P table.Can someone tell me something about these
tables.
Or can someone can tell me which function can come in handy,or where to look
in.
I am in the middle of  a project that needs to manipulate the page table in
dom.
For example,
static unsigned long
dbg_pv_va2mfn(dbgva_t vaddr, struct domain *dp, uint64_t pgd3val)
{
    l3_pgentry_t l3e, *l3t;
    l2_pgentry_t l2e, *l2t;
    l1_pgentry_t l1e, *l1t;
    unsigned long cr3 = (pgd3val ? pgd3val : dp->vcpu[0]->arch.cr3);
    unsigned long mfn = cr3 >> PAGE_SHIFT;

    DBGP2("vaddr:%lx domid:%d cr3:%lx pgd3:%lx\n", vaddr, dp->domain_id,
          cr3, pgd3val);

    if ( pgd3val == 0 )
    {
        l3t  = map_domain_page(mfn);
        l3t += (cr3 & 0xFE0UL) >> 3;
        l3e = l3t[l3_table_offset(vaddr)];
        mfn = l3e_get_pfn(l3e);
        unmap_domain_page(l3t);
        if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) )
            return INVALID_MFN;
    }

    l2t = map_domain_page(mfn);
    l2e = l2t[l2_table_offset(vaddr)];
    mfn = l2e_get_pfn(l2e);
    unmap_domain_page(l2t);
    if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
         (l2e_get_flags(l2e) & _PAGE_PSE) )
        return INVALID_MFN;

    l1t = map_domain_page(mfn);
    l1e = l1t[l1_table_offset(vaddr)];----------------------------------(1)
    mfn = l1e_get_pfn(l1e);----------------------------------------------(2)

    unmap_domain_page(l1t);

    return mfn_valid(mfn) ? mfn : INVALID_MFN;
}
What should i do if i want to change the l1e page table entry.I allocate a
page using the function alloc_domheap_page,and use l1e_from_page() to write
the l1e entry,but it proved to be wrong,and my system keeps reboot itself.
Can anyone gives me a hand?


                       Thanks

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