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	*
		46	* Architectures that don't have hardware support for address
		47	* spaces do not compile with this file.
		48	*/
		49
		50	#include <mm/asid.h>
		51	#include <mm/as.h>
		52	#include <mm/tlb.h>
		53	#include <arch/mm/asid.h>
		54	#include <synch/spinlock.h>
		55	#include <arch.h>
		56	#include <list.h>
		57	#include <debug.h>
		58
		59	/**
		60	* asidlock protects both the asids_allocated counter
		61	* and the list of address spaces that were already
		62	* assigned ASID.
		63	*/
		64	SPINLOCK_INITIALIZE(asidlock);
		65
		66	static count_t asids_allocated = 0;
		67
		68	/**
		69	* List of address spaces with assigned ASID.
		70	* When the system runs short of allocable
		71	* ASIDS, inactive address spaces are guaranteed
		72	* to be at the beginning of the list.
		73	*/
		74	LIST_INITIALIZE(as_with_asid_head);
		75
		76
		77	/** Allocate free address space identifier.
		78	*
		79	* This code depends on the fact that ASIDS_ALLOCABLE
		80	* is greater than number of supported CPUs.
		81	*
		82	* @return New ASID.
		83	*/
		84	asid_t asid_get(void)
		85	{
		86	ipl_t ipl;
		87	asid_t asid;
		88	link_t *tmp;
		89	as_t *as;
		90
		91	/*
		92	* Check if there is an unallocated ASID.
		93	*/
		94
		95	ipl = interrupts_disable();
		96	spinlock_lock(&asidlock);
		97	if (asids_allocated == ASIDS_ALLOCABLE) {
		98
		99	/*
		100	* All ASIDs are already allocated.
		101	* Resort to stealing.
		102	*/
		103
		104	/*
		105	* Remove the first item on the list.
		106	* It is guaranteed to belong to an
		107	* inactive address space.
		108	*/
		109	tmp = as_with_asid_head.next;
		110	ASSERT(tmp != &as_with_asid_head);
		111	list_remove(tmp);
		112
		113	as = list_get_instance(tmp, as_t, as_with_asid_link);
		114	spinlock_lock(&as->lock);
		115
		116	/*
		117	* Steal the ASID.
		118	* Note that the stolen ASID is not active.
		119	*/
		120	asid = as->asid;
		121	ASSERT(asid != ASID_INVALID);
		122
		123	/*
		124	* Get the system rid of the stolen ASID.
		125	*/
		126	tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
		127	tlb_shootdown_finalize();
		128	as->asid = ASID_INVALID;
		129
		130	spinlock_unlock(&as->lock);
		131	} else {
		132
		133	/*
		134	* There is at least one unallocated ASID.
		135	* Find it and assign it.
		136	*/
		137
		138	asid = asid_find_free();
		139	asids_allocated++;
		140	}
		141
		142	spinlock_unlock(&asidlock);
		143	interrupts_restore(ipl);
		144
		145	return asid;
		146	}
		147
		148	/** Release address space identifier.
		149	*
		150	* This code relies on architecture
		151	* dependent functionality.
		152	*
		153	* @param asid ASID to be released.
		154	*/
		155	void asid_put(asid_t asid)
		156	{
		157	ipl_t ipl;
		158
		159	ipl = interrupts_disable();
		160	spinlock_lock(&asidlock);
		161
		162	asids_allocated--;
		163	asid_put_arch(asid);
		164
		165	spinlock_unlock(&asidlock);
		166	interrupts_restore(ipl);
		167	}
		168
		169	/** Install ASID.
		170	*
		171	* This function is to be executed on each address space switch.
		172	*
		173	* @param as Address space.
		174	*/
		175	void asid_install(as_t *as)
		176	{
		177	ipl_t ipl;
		178
		179	ipl = interrupts_disable();
		180	spinlock_lock(&asidlock);
		181	spinlock_lock(&as->lock);
		182
		183	if (as->asid != ASID_KERNEL) {
		184	if (as->asid != ASID_INVALID) {
		185	/*
		186	* This address space has valid ASID.
		187	* Remove 'as' from the list of address spaces
		188	* with assigned ASID, so that it can be later
		189	* appended to the tail of the same list.
		190	* This is to prevent stealing of ASIDs from
		191	* recently installed address spaces.
		192	*/
		193	list_remove(&as->as_with_asid_link);
		194	} else {
		195	spinlock_unlock(&as->lock);
		196	spinlock_unlock(&asidlock);
		197
		198	/*
		199	* This address space doesn't have ASID assigned.
		200	* It was stolen or the address space is being
		201	* installed for the first time.
		202	* Allocate new ASID for it.
		203	*/
		204	as->asid = asid_get();
		205	spinlock_lock(&asidlock);
		206	spinlock_lock(&as->lock);
		207	}
		208
		209	/*
		210	* Now it is sure that 'as' has ASID.
		211	* It is therefore appended to the list
		212	* of address spaces from which it can
		213	* be stolen.
		214	*/
		215	list_append(&as->as_with_asid_link, &as_with_asid_head);
		216	}
		217
		218	spinlock_unlock(&as->lock);
		219	spinlock_unlock(&asidlock);
		220	interrupts_restore(ipl);
		221	}

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