kmap_atomic issue with SLES11SP1 32bit XEN driver code

[dbrace <dab@hp.com>]

kernel: Linux 360 2.6.32.12-0.7-xen #1 SMP 2010-05-20 11:14:20 +0200 
i686 i686 i386 GNU/Linux

I am having issues with some code that uses kmap_atomic(). I am getting:

BUG: unable to handle kernel paging request at 23a1a000 (which is the 
address returned from kmap_atomic().)

The same code works when running on non-XEN 32bit kernels so I am  
wondering why this does not work under
XEN kernels. Is there a different approach that I need to take for 32bit 
XEN kernels?

I really only need to do this code segment if the memory address is a 
high memory address. Is there a MACRO or function
that can help me determine this?

Here is a code snippet:

                 void *linux_vaddr = NULL;       /* kmapped temporary 
virtual address */
                 int linux_page_offset = 0;      /* offset in page */
                 int count = 0;                  /* bytes left to 
transfer */
                 int left = byte_count;          /* number of bytes left 
to transfer */
                 int memcpysize = 0;             /* current size to 
transfer */
                 struct page *linux_page = NULL; /* calculated page */
                 int kmap_flags = 0;

                 linux_page = __pfn_to_page(physical_address >> PAGE_SHIFT);
                 linux_page_offset = (physical_address & 
0x0000000000000FFFULL);
                 memcpysize =  min((PAGE_SIZE - linux_page_offset), left);

                 kmap_flags = KM_USER0;

                 linux_vaddr = kmap_atomic(linux_page, kmap_flags) + 
linux_page_offset;

                 printk("%s: called kmap_atomic, "
                         "calling memcpy linux_vaddr = 0x%x virt_address 
= 0x%x count = 0x%x\n",
                         __func__, linux_vaddr, virt_address, count);
                 /*
                  * Either need to copy to a kmapped destination
                  * or a kmapped source.
                  */
                 if (type == 0) // Write to s/g element, dest virtual 
addr was known.
                         memcpy((void *)virt_address+count, (void 
*)linux_vaddr, memcpysize);
                 else // Source virt. address was known.
                         memcpy((void *)linux_vaddr, (void 
*)virt_address+count, memcpysize);

                 printk("OS_Linux32_Xfer_SG_Page: calling kunmap_atomic, "
                         "calling memcpy linux_vaddr = 0x%lx\n", 
linux_vaddr);

                 kunmap_atomic(linux_vaddr, kmap_flags);


-- 
Don Brace
SPSN Linux Development
Hewlett-Packard Company