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
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>
		60	#include <arch.h>
788	jermar	61	#include <adt/list.h>
727	jermar	62	#include <debug.h>
		63
		64	/**
823	jermar	65	* asidlock protects the asids_allocated counter.
727	jermar	66	*/
		67	SPINLOCK_INITIALIZE(asidlock);
		68
		69	static count_t asids_allocated = 0;
		70
		71	/** Allocate free address space identifier.
		72	*
823	jermar	73	* Interrupts must be disabled and as_lock must be held
		74	* prior to this call
727	jermar	75	*
		76	* @return New ASID.
		77	*/
		78	asid_t asid_get(void)
		79	{
		80	asid_t asid;
		81	link_t *tmp;
		82	as_t *as;
		83
		84	/*
		85	* Check if there is an unallocated ASID.
		86	*/
		87
		88	spinlock_lock(&asidlock);
753	jermar	89	if (asids_allocated == ASIDS_ALLOCABLE) {
727	jermar	90
		91	/*
		92	* All ASIDs are already allocated.
		93	* Resort to stealing.
		94	*/
		95
		96	/*
		97	* Remove the first item on the list.
		98	* It is guaranteed to belong to an
		99	* inactive address space.
		100	*/
823	jermar	101	ASSERT(!list_empty(&inactive_as_with_asid_head));
		102	tmp = inactive_as_with_asid_head.next;
727	jermar	103	list_remove(tmp);
		104
823	jermar	105	as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
727	jermar	106	spinlock_lock(&as->lock);
		107
		108	/*
		109	* Steal the ASID.
		110	* Note that the stolen ASID is not active.
		111	*/
		112	asid = as->asid;
		113	ASSERT(asid != ASID_INVALID);
		114
		115	/*
741	jermar	116	* Notify the address space from wich the ASID
		117	* was stolen by invalidating its asid member.
		118	*/
		119	as->asid = ASID_INVALID;
		120	spinlock_unlock(&as->lock);
		121
		122	/*
727	jermar	123	* Get the system rid of the stolen ASID.
		124	*/
		125	tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
		126	tlb_shootdown_finalize();
740	jermar	127	tlb_invalidate_asid(asid);
727	jermar	128	} else {
		129
		130	/*
		131	* There is at least one unallocated ASID.
		132	* Find it and assign it.
		133	*/
		134
		135	asid = asid_find_free();
		136	asids_allocated++;
		137	}
		138
		139	spinlock_unlock(&asidlock);
		140
		141	return asid;
		142	}
		143
		144	/** Release address space identifier.
		145	*
		146	* This code relies on architecture
		147	* dependent functionality.
		148	*
		149	* @param asid ASID to be released.
		150	*/
		151	void asid_put(asid_t asid)
		152	{
		153	ipl_t ipl;
		154
		155	ipl = interrupts_disable();
		156	spinlock_lock(&asidlock);
		157
		158	asids_allocated--;
		159	asid_put_arch(asid);
		160
		161	spinlock_unlock(&asidlock);
		162	interrupts_restore(ipl);
		163	}

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