pmap of amd64

Yonghong Yan noah.yan at
Tue Oct 16 14:46:11 PDT 2007

Hi Matt,

lots of things hang me around by the department open house.
thanks for your suggestions. some of them i am not fully understand,
but prefer to hold my questions until i see that it starting to
trouble me :).

will start with the simple solution first and then move on to
something complicated.


On 10/12/07, Matthew Dillon <dillon at> wrote:
>     I should add a clarification regarding the per-cpu info.  I think the
>     distinction should be as a separate PML4 entry and not a PDP entry.  This
>     way the kernel can have a single PDP/PD hierarchy that is shared across
>     all cpus.
>     The per-cpu magic can be statically hardwired for each cpu via a PML4
>     entry and maybe a few other pages (per-cpu) creating a PDP/PD
>     hierarchy.   There are two ways to do it.
>     (1) We can map a page containing the address of the per-cpu globaldata
>         structure and use %fs in the trap code:
>         movq    $SOME_FIXED_CONSTANT_ADDRESS,%fs
>     (2) We can map the actual per-cpu globaldata to a fixed address and access
>         it directly.
>     Either way will work.  I will note that the system code expects 'mycpu'
>     to be a variable kernel space address representing the location of the
>     globaldata structure in kernel space and it will get confusde if
>     'mycpu' returns the same fixed address on every cpu.  So the %fs method
>     may be the best way to go so we don't have to run through all the system
>     code changing the expectations for 'mycpu'.
>                                                         -Matt

More information about the Kernel mailing list