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				.\"
				.\" Copyright (c) 2015 Jason A. Harmening <jah@FreeBSD.org>
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				.\" $FreeBSD$
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				.Dd August 6, 2015
				.Dt PMAP_QUICK_ENTER_PAGE 9
				.Os
				.Sh NAME
				.Nm pmap_quick_enter_page ,
				.Nm pmap_quick_remove_page
				.Nd manage fast, single-page kernel address space mappings
				.Sh SYNOPSIS
				.In sys/param.h
				.In vm/vm.h
				.In vm/pmap.h
				.Ft vm_offset_t
				.Fn pmap_quick_enter_page "vm_page_t m"
				.Ft void
				.Fn pmap_quick_remove_page "vm_offset_t kva"
				.Sh DESCRIPTION
				The
				.Fn pmap_quick_enter_page
				function accepts a single page
				.Fa 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.
				.Pp
				The
				.Fn pmap_quick_remove_page
				function removes a mapping previously created by
				.Fn pmap_quick_enter_page
				at
				.Fa kva ,
				making the KVA frame used by
				.Fn pmap_quick_enter_page
				available for reuse.
				.Pp
				On many architectures,
				.Fn pmap_quick_enter_page
				uses a per-CPU pageframe.
				In those cases, it must disable preemption on the local CPU.
				The corresponding call to
				.Fn 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
				.Fn pmap_quick_enter_page
				must not be nested.
				.Pp
				.Fn pmap_quick_enter_page
				and
				.Fn pmap_quick_remove_page
				do not sleep, and
				.Fn 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.
				.Pp
				The page
				.Em 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.
				.Sh RETURN VALUES
				The
				.Fn pmap_quick_enter_page
				function returns the kernel virtual address
				that is mapped to the page
				.Fa m .
				.Sh SEE ALSO
				.Xr pmap 9
				.Sh AUTHORS
				This manual page was written by
				.An Jason A Harmening Aq Mt jah@FreeBSD.org .