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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 14.0-RELEASE-p11 August 6, 2015 FreeBSD 14.0-RELEASE-p11