how to transfer virtual address into pyhsical address

[Yong LIU <yongliu@cs.uit.no>]

I write a very simple module to test memory address translation.
When I install the module under xen 3.0, kernel panic. But when
I install it under xen3.0 & kernel 2.6.16-rc2, it can work well.

My question is: Is there a different way to translate virtual address
into physical address under Xen 3.0?
thanks for help. 

dmesg information.
--------------------------------------------------------
hello: module license 'unspecified' taints kernel.
Unable to handle kernel paging request at virtual address 3e0c5b0c
 printing eip:
f483c023
*pde = ma 00000000 pa 55555000
Oops: 0000 [#1]
SMP
Modules linked in: hello iptable_filter ip_tables video thermal
processor fan button battery ac
CPU:    1
EIP:    0061:[<f483c023>]    Tainted: P      VLI
EFLAGS: 00010206   (2.6.12.6-xen0-smp)
EIP is at kvirt_to_pa+0x23/0x3c [hello]
eax: 7e0c5000   ebx: f22c3000   ecx: 00000b0c   edx: 000003c8
esi: f2026000   edi: c0000000   ebp: f2026000   esp: f2027f90
ds: 007b   es: 007b   ss: 0069
Process insmod (pid: 4710, threadinfo=f2026000 task=f27c4520)
Stack: f483e01a f22c3000 f483c380 c013a1f8 c05a10a8 00000001 f483c380
0804a060
       b7fb3ff4 b7fb5538 c0109021 0804a060 00000dda 0804a050 b7fb3ff4
b7fb5538
       bffd6558 00000080 0000007b c010007b 00000080 b7f5667e 00000073
00010246
Call Trace:
 [<f483e01a>] hello_init_module+0x1a/0x2d [hello]
 [<c013a1f8>] sys_init_module+0x145/0x1e1
 [<c0109021>] syscall_call+0x7/0xb
Code:  Bad EIP value.
-------------------------------------------------------
here is the code.
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>

#include <asm/pgtable.h>
#include <asm/page.h>

static void kvirt_to_pa(void *vaddr)
{
        unsigned long addr=(unsigned long) vaddr;
        unsigned long pte_value;
        pgd_t *pgd=NULL;
        pmd_t *pmd=NULL;
        pte_t *pte=NULL;

        pgd=pgd_offset_k(addr);
        if(pgd_none(*pgd))
                goto hello_failed;
        pmd=pmd_offset(pgd, addr);
        if(pmd_none(*pmd))
                goto hello_failed;
        pte=pte_offset_kernel(pmd, addr);
        if(!pte_present(*pte))
                goto hello_failed;

        pte_value= pte_val(*pte) & PAGE_MASK | (addr & (PAGE_SIZE - 1));
        return;

hello_failed:
        printk(" failed\n");
        return;
}
static int __init hello_init_module(void)
{
        void * page=NULL;
        page=__get_free_pages(GFP_KERNEL, 0);
        kvirt_to_pa(page);
        free_page(page);
        return 1;
}


static void __exit hello_exit_module(void)
{
        printk(" say bye\n");
        return;
}
module_init(hello_init_module);
module_exit(hello_exit_module);