PMAP_QUICK_ENTER_PAGE(9)                     FreeBSD Kernel Developer's Manual

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>.

FreeBSD 13.1-RELEASE-p6         August 6, 2015         FreeBSD 13.1-RELEASE-p6