One of our engineers, Maciek, is working on a driver and stumbled upon what 
looks like a bug in the Xen kernel.  The report I got was:

We recently started to provide mmap functionality in our driver for Linux. 
Function for this:

int
NalMmap(
    struct file*                            File,
    struct vm_area_struct*  Vma
    )
{
    if(remap_pfn_range(Vma,
        Vma->vm_start,
        Vma->vm_pgoff,
        Vma->vm_end - Vma->vm_start,
        Vma->vm_page_prot))
    {
        return -EAGAIN;
    }

    return 0;
}

We discovered that this doesn't work for xen kernels (but it doesn't return any 
error, just does not map). I found that it is suggested to use 
io_remap_pfn_range instead of remap_pfn_range. After switching function 
everything still works on standard kernel, but on xen this time it returns 
error.

--
Don Dugger
"Censeo Toto nos in Kansa esse decisse." - D. Gale
Ph: 303/443-3786

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