NAME

       pmap_quick_enter_page, pmap_quick_remove_page — manage fast, single-page kernel address space mappings

SYNOPSIS

       #include <sys/param.h>
       #include <vm/vm.h>
       #include <vm/pmap.h>

       vm_offset_t
       pmap_quick_enter_page(vm_page_t m);

       void
       pmap_quick_remove_page(vm_offset_t kva);

DESCRIPTION

       The  pmap_quick_enter_page()  function  accepts a single page m, and enters this page into a preallocated
       address in kernel virtual address (KVA) space.  This function is intended  for  temporary  mappings  that
       will only be used for a very short period, for example a copy operation on the page contents.

       The  pmap_quick_remove_page() function removes a mapping previously created by pmap_quick_enter_page() at
       kva, making the KVA frame used by pmap_quick_enter_page() available for reuse.

       On many architectures, pmap_quick_enter_page() uses a per-CPU pageframe.  In those cases, it must disable
       preemption on the  local  CPU.   The  corresponding  call  to  pmap_quick_remove_page()  then  re-enables
       preemption.  It is therefore not safe for machine-independent code to sleep or perform locking operations
       while  holding  these mappings.  Current implementations only guarantee the availability of a single page
       for the calling thread, so calls to pmap_quick_enter_page() must not be nested.

       pmap_quick_enter_page() and pmap_quick_remove_page() do not  sleep,  and  pmap_quick_enter_page()  always
       returns a valid address.  It is safe to use these functions under all types of locks except spin mutexes.
       It is also safe to use them in all thread contexts except primary interrupt context.

       The page must not be swapped or otherwise reused while the mapping is active.  It must be either wired or
       held, or it must belong to an unmanaged region such as I/O device memory.

RETURN VALUES

       The pmap_quick_enter_page() function returns the kernel virtual address that is mapped to the page m.

SEE ALSO

       pmap(9)

AUTHORS

       This manual page was written by Jason A Harmening <jah@FreeBSD.org>.

Debian                                           August 6, 2015                         PMAP_QUICK_ENTER_PAGE(9)