1.\" 2.\" Copyright (c) 2015 Jason A. Harmening <jah@FreeBSD.org> 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.Dd August 6, 2015 27.Dt PMAP_QUICK_ENTER_PAGE 9 28.Os 29.Sh NAME 30.Nm pmap_quick_enter_page , 31.Nm pmap_quick_remove_page 32.Nd manage fast, single-page kernel address space mappings 33.Sh SYNOPSIS 34.In sys/param.h 35.In vm/vm.h 36.In vm/pmap.h 37.Ft vm_offset_t 38.Fn pmap_quick_enter_page "vm_page_t m" 39.Ft void 40.Fn pmap_quick_remove_page "vm_offset_t kva" 41.Sh DESCRIPTION 42The 43.Fn pmap_quick_enter_page 44function accepts a single page 45.Fa m , 46and enters this page into a preallocated address in kernel virtual 47address (KVA) space. 48This function is intended for temporary mappings that will only 49be used for a very short period, for example a copy operation on 50the page contents. 51.Pp 52The 53.Fn pmap_quick_remove_page 54function removes a mapping previously created by 55.Fn pmap_quick_enter_page 56at 57.Fa kva , 58making the KVA frame used by 59.Fn pmap_quick_enter_page 60available for reuse. 61.Pp 62On many architectures, 63.Fn pmap_quick_enter_page 64uses a per-CPU pageframe. 65In those cases, it must disable preemption on the local CPU. 66The corresponding call to 67.Fn pmap_quick_remove_page 68then re-enables preemption. 69It is therefore not safe for machine-independent code to sleep 70or perform locking operations while holding these mappings. 71Current implementations only guarantee the availability of a single 72page for the calling thread, so calls to 73.Fn pmap_quick_enter_page 74must not be nested. 75.Pp 76.Fn pmap_quick_enter_page 77and 78.Fn pmap_quick_remove_page 79do not sleep, and 80.Fn pmap_quick_enter_page 81always returns a valid address. 82It is safe to use these functions under all types of locks except spin mutexes. 83It is also safe to use them in all thread contexts except primary interrupt 84context. 85.Pp 86The page 87.Em must 88not be swapped or otherwise reused while the mapping is active. 89It must be either wired or held, or it must belong to an unmanaged 90region such as I/O device memory. 91.Sh RETURN VALUES 92The 93.Fn pmap_quick_enter_page 94function returns the kernel virtual address 95that is mapped to the page 96.Fa m . 97.Sh SEE ALSO 98.Xr pmap 9 99.Sh AUTHORS 100This manual page was written by 101.An Jason A Harmening Aq Mt jah@FreeBSD.org . 102