Problem using alloc_vm_area()

[Lamia Youseff <lyouseff@cs.ucsb.edu>]

Hi all,

I am having trouble mapping an area allocated by vmalloc_alloc_area to
user space. I would appreciate any help or hint on what i might be
missing in my implementation.

Inside my device_mmap, this is what i do.
I first allocate memory using
1. mem = alloc_vm_area( 1 * PAGE_SIZE );


then i get pfn using vmalloc_to_pfn,
2. pfn = vmalloc_to_pfn((struct vm_struct*)mem)->addr);

then, i try to map it using
3. ret = remap_pfn_range(vma, vma->start, pfn, PAGE_SIZE,
                                  PAGE_SHARED);

Although remap_pfn_range does not return an error, the DomU kernel
randomly crashes, or if it worked, it is not mapped to user-space
correctly. I need your advise on line 2 & 3, if possible. Please, let me
know if i can provide more information,

Thank you,
-- Lamia