kernel "logical" versus "virtual" addresses

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



  i want to clarify some terminology since i'm hearing different
explanations from different colleagues and i already know what *i*
think is correct.

  given the (typical) kernel address space in the range 3G-4G, it's
safe to say that, on most machines, all of the addresses in that
interval are "virtual" addresses which must be mapped somehow to
produce the corresponding physical address.  but those "virtual"
addresses fall into two categories.

  if the address is simply reduced by the offset of 0xc0000000 (on
x86) to produce the physical address, this is what most of the
literature refers to as a "logical" address.  if, instead, the address
has to be mapped through the kernel page tables to perhaps access high
memory, this is often described as a "virtual" address.

  in short, while all the addresses in kernel space are technically
"virtual" addresses, some of them are the simple offset-based ones
which are additionally referred to as "logical" addresses.

  is that a fair way to look at it?  thanks.

rday

p.s.  another way to look at it is that logical addresses *must* map
to somewhere in the first 1G of RAM, while virtual addresses don't
have to.

-- 
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA

http://fsdev.net/wiki/index.php?title=Main_Page
========================================================================

--
To unsubscribe from this list: send an email with
"unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx
Please read the FAQ at http://kernelnewbies.org/FAQ


[Index of Archives]     [Newbies FAQ]     [Linux Kernel Mentors]     [Linux Kernel Development]     [IETF Annouce]     [Git]     [Networking]     [Security]     [Bugtraq]     [Yosemite]     [MIPS Linux]     [ARM Linux]     [Linux RAID]     [Linux SCSI]     [Linux ACPI]
  Powered by Linux