WebSVN – HelenOS – Blame – /trunk/kernel/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
1266	jermar	29	/**
		30	* @file asid.c
		31	* @brief ASID management.
727	jermar	32	*
		33	* Modern processor architectures optimize TLB utilization
		34	* by using ASIDs (a.k.a. memory contexts on sparc64 and
		35	* region identifiers on ia64). These ASIDs help to associate
		36	* each TLB item with an address space, thus making
		37	* finer-grained TLB invalidation possible.
		38	*
		39	* Unfortunatelly, there are usually less ASIDs available than
		40	* there can be unique as_t structures (i.e. address spaces
		41	* recognized by the kernel).
		42	*
		43	* When system runs short of ASIDs, it will attempt to steal
		44	* ASID from an address space that has not been active for
		45	* a while.
		46	*
823	jermar	47	* This code depends on the fact that ASIDS_ALLOCABLE
		48	* is greater than number of supported CPUs (i.e. the
		49	* amount of concurently active address spaces).
		50	*
727	jermar	51	* Architectures that don't have hardware support for address
		52	* spaces do not compile with this file.
		53	*/
		54
		55	#include <mm/asid.h>
		56	#include <mm/as.h>
		57	#include <mm/tlb.h>
		58	#include <arch/mm/asid.h>
		59	#include <synch/spinlock.h>
1380	jermar	60	#include <synch/mutex.h>
727	jermar	61	#include <arch.h>
788	jermar	62	#include <adt/list.h>
727	jermar	63	#include <debug.h>
		64
		65	/**
823	jermar	66	* asidlock protects the asids_allocated counter.
727	jermar	67	*/
		68	SPINLOCK_INITIALIZE(asidlock);
		69
		70	static count_t asids_allocated = 0;
		71
		72	/** Allocate free address space identifier.
		73	*
823	jermar	74	* Interrupts must be disabled and as_lock must be held
		75	* prior to this call
727	jermar	76	*
		77	* @return New ASID.
		78	*/
		79	asid_t asid_get(void)
		80	{
		81	asid_t asid;
		82	link_t *tmp;
		83	as_t *as;
		84
		85	/*
		86	* Check if there is an unallocated ASID.
		87	*/
		88
		89	spinlock_lock(&asidlock);
753	jermar	90	if (asids_allocated == ASIDS_ALLOCABLE) {
727	jermar	91
		92	/*
		93	* All ASIDs are already allocated.
		94	* Resort to stealing.
		95	*/
		96
		97	/*
		98	* Remove the first item on the list.
		99	* It is guaranteed to belong to an
		100	* inactive address space.
		101	*/
823	jermar	102	ASSERT(!list_empty(&inactive_as_with_asid_head));
		103	tmp = inactive_as_with_asid_head.next;
727	jermar	104	list_remove(tmp);
		105
823	jermar	106	as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
1380	jermar	107	mutex_lock_active(&as->lock);
727	jermar	108
		109	/*
		110	* Steal the ASID.
		111	* Note that the stolen ASID is not active.
		112	*/
		113	asid = as->asid;
		114	ASSERT(asid != ASID_INVALID);
		115
		116	/*
741	jermar	117	* Notify the address space from wich the ASID
		118	* was stolen by invalidating its asid member.
		119	*/
		120	as->asid = ASID_INVALID;
1380	jermar	121	mutex_unlock(&as->lock);
741	jermar	122
		123	/*
727	jermar	124	* Get the system rid of the stolen ASID.
		125	*/
		126	tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
		127	tlb_shootdown_finalize();
740	jermar	128	tlb_invalidate_asid(asid);
727	jermar	129	} else {
		130
		131	/*
		132	* There is at least one unallocated ASID.
		133	* Find it and assign it.
		134	*/
		135
		136	asid = asid_find_free();
		137	asids_allocated++;
		138	}
		139
		140	spinlock_unlock(&asidlock);
		141
		142	return asid;
		143	}
		144
		145	/** Release address space identifier.
		146	*
		147	* This code relies on architecture
		148	* dependent functionality.
		149	*
		150	* @param asid ASID to be released.
		151	*/
		152	void asid_put(asid_t asid)
		153	{
		154	ipl_t ipl;
		155
		156	ipl = interrupts_disable();
		157	spinlock_lock(&asidlock);
		158
		159	asids_allocated--;
		160	asid_put_arch(asid);
		161
		162	spinlock_unlock(&asidlock);
		163	interrupts_restore(ipl);
		164	}

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