one question about shared mappings between user space and kernel space.

[Peter Chacko]

Hi kernel geeks,

Please forgive me if this questions was asked already in the past !!!

I  have a question about shared memory mappings between kernel and
user process...(.like accessing device memory directly from user space
through device mmap interface)...I  presume this mechanism use
remap_pfn_range() or similar....when such mappings are in place, (
whats the "U/S" flag in the underlying physical page indicating CPL of
the page) for such pages ? such page  descriptors  are stored in
normal GDT  or considered as global pages ? Any special  policies of
TLB flush of  translations to such pages ?

With a shared memory between user process and kernel using such
mechanism, is it equivalent to  zero-copy transfer between user space
and kernel space? ( I mean any extra overhead in  memory access to
such pages)

I would appreciate your thoughts on this.

-- 
Best regards,
Peter Chacko

NetDiox computing systems,
Network storage & OS  training and research.
Bangalore, India.
www.netdiox.com
080 2664 0708
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/