WebSVN – HelenOS-historic – Blame – /kernel/trunk/genarch/src/mm/asid.c

Rev	Author	Line No.	Line
727	jermar	1	/*
		2	* Copyright (C) 2006 Jakub Jermar
		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	*
		9	* - Redistributions of source code must retain the above copyright
		10	* notice, this list of conditions and the following disclaimer.
		11	* - Redistributions in binary form must reproduce the above copyright
		12	* notice, this list of conditions and the following disclaimer in the
		13	* documentation and/or other materials provided with the distribution.
		14	* - The name of the author may not be used to endorse or promote products
		15	* derived from this software without specific prior written permission.
		16	*
		17	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
		18	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
		19	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
		20	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
		21	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
		22	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
		23	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
		24	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
		25	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
		26	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
		27	*/
		28
		29	/*
		30	* ASID management.
		31	*
		32	* Modern processor architectures optimize TLB utilization
		33	* by using ASIDs (a.k.a. memory contexts on sparc64 and
		34	* region identifiers on ia64). These ASIDs help to associate
		35	* each TLB item with an address space, thus making
		36	* finer-grained TLB invalidation possible.
		37	*
		38	* Unfortunatelly, there are usually less ASIDs available than
		39	* there can be unique as_t structures (i.e. address spaces
		40	* recognized by the kernel).
		41	*
		42	* When system runs short of ASIDs, it will attempt to steal
		43	* ASID from an address space that has not been active for
		44	* a while.
		45	*
823	jermar	46	* This code depends on the fact that ASIDS_ALLOCABLE
		47	* is greater than number of supported CPUs (i.e. the
		48	* amount of concurently active address spaces).
		49	*
727	jermar	50	* Architectures that don't have hardware support for address
		51	* spaces do not compile with this file.
		52	*/
		53
		54	#include <mm/asid.h>
		55	#include <mm/as.h>
		56	#include <mm/tlb.h>
		57	#include <arch/mm/asid.h>
		58	#include <synch/spinlock.h>
		59	#include <arch.h>
788	jermar	60	#include <adt/list.h>
727	jermar	61	#include <debug.h>
		62
		63	/**
823	jermar	64	* asidlock protects the asids_allocated counter.
727	jermar	65	*/
		66	SPINLOCK_INITIALIZE(asidlock);
		67
		68	static count_t asids_allocated = 0;
		69
		70	/** Allocate free address space identifier.
		71	*
823	jermar	72	* Interrupts must be disabled and as_lock must be held
		73	* prior to this call
727	jermar	74	*
		75	* @return New ASID.
		76	*/
		77	asid_t asid_get(void)
		78	{
		79	asid_t asid;
		80	link_t *tmp;
		81	as_t *as;
		82
		83	/*
		84	* Check if there is an unallocated ASID.
		85	*/
		86
		87	spinlock_lock(&asidlock);
753	jermar	88	if (asids_allocated == ASIDS_ALLOCABLE) {
727	jermar	89
		90	/*
		91	* All ASIDs are already allocated.
		92	* Resort to stealing.
		93	*/
		94
		95	/*
		96	* Remove the first item on the list.
		97	* It is guaranteed to belong to an
		98	* inactive address space.
		99	*/
823	jermar	100	ASSERT(!list_empty(&inactive_as_with_asid_head));
		101	tmp = inactive_as_with_asid_head.next;
727	jermar	102	list_remove(tmp);
		103
823	jermar	104	as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
727	jermar	105	spinlock_lock(&as->lock);
		106
		107	/*
		108	* Steal the ASID.
		109	* Note that the stolen ASID is not active.
		110	*/
		111	asid = as->asid;
		112	ASSERT(asid != ASID_INVALID);
		113
		114	/*
741	jermar	115	* Notify the address space from wich the ASID
		116	* was stolen by invalidating its asid member.
		117	*/
		118	as->asid = ASID_INVALID;
		119	spinlock_unlock(&as->lock);
		120
		121	/*
727	jermar	122	* Get the system rid of the stolen ASID.
		123	*/
		124	tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
		125	tlb_shootdown_finalize();
740	jermar	126	tlb_invalidate_asid(asid);
727	jermar	127	} else {
		128
		129	/*
		130	* There is at least one unallocated ASID.
		131	* Find it and assign it.
		132	*/
		133
		134	asid = asid_find_free();
		135	asids_allocated++;
		136	}
		137
		138	spinlock_unlock(&asidlock);
		139
		140	return asid;
		141	}
		142
		143	/** Release address space identifier.
		144	*
		145	* This code relies on architecture
		146	* dependent functionality.
		147	*
		148	* @param asid ASID to be released.
		149	*/
		150	void asid_put(asid_t asid)
		151	{
		152	ipl_t ipl;
		153
		154	ipl = interrupts_disable();
		155	spinlock_lock(&asidlock);
		156
		157	asids_allocated--;
		158	asid_put_arch(asid);
		159
		160	spinlock_unlock(&asidlock);
		161	interrupts_restore(ipl);
		162	}

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