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| /* |
| * Copyright (C) 2006 Jakub Jermar |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * - Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in the |
| * documentation and/or other materials provided with the distribution. |
| * - The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
| * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
| * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
| * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
| * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
| * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| /* |
| * ASID management. |
| * |
| * Modern processor architectures optimize TLB utilization |
| * by using ASIDs (a.k.a. memory contexts on sparc64 and |
| * region identifiers on ia64). These ASIDs help to associate |
| * each TLB item with an address space, thus making |
| * finer-grained TLB invalidation possible. |
| * |
| * Unfortunatelly, there are usually less ASIDs available than |
| * there can be unique as_t structures (i.e. address spaces |
| * recognized by the kernel). |
| * |
| * When system runs short of ASIDs, it will attempt to steal |
| * ASID from an address space that has not been active for |
| * a while. |
| * |
| * Architectures that don't have hardware support for address |
| * spaces do not compile with this file. |
| */ |
| |
| #include <mm/asid.h> |
| #include <mm/as.h> |
| #include <mm/tlb.h> |
| #include <arch/mm/asid.h> |
| #include <synch/spinlock.h> |
| #include <arch.h> |
| #include <list.h> |
| #include <debug.h> |
| |
| /** |
| * asidlock protects both the asids_allocated counter |
| * and the list of address spaces that were already |
| * assigned ASID. |
| */ |
| SPINLOCK_INITIALIZE(asidlock); |
| |
| static count_t asids_allocated = 0; |
| |
| /** |
| * List of address spaces with assigned ASID. |
| * When the system runs short of allocable |
| * ASIDS, inactive address spaces are guaranteed |
| * to be at the beginning of the list. |
| */ |
| LIST_INITIALIZE(as_with_asid_head); |
| |
| |
| /** Allocate free address space identifier. |
| * |
| * This code depends on the fact that ASIDS_ALLOCABLE |
| * is greater than number of supported CPUs. |
| * |
| * @return New ASID. |
| */ |
| asid_t asid_get(void) |
| { |
| ipl_t ipl; |
| asid_t asid; |
| link_t *tmp; |
| as_t *as; |
| |
| /* |
| * Check if there is an unallocated ASID. |
| */ |
| |
| ipl = interrupts_disable(); |
| spinlock_lock(&asidlock); |
| if (asids_allocated == ASIDS_ALLOCABLE) { |
| |
| /* |
| * All ASIDs are already allocated. |
| * Resort to stealing. |
| */ |
| |
| /* |
| * Remove the first item on the list. |
| * It is guaranteed to belong to an |
| * inactive address space. |
| */ |
| tmp = as_with_asid_head.next; |
| ASSERT(tmp != &as_with_asid_head); |
| list_remove(tmp); |
| |
| as = list_get_instance(tmp, as_t, as_with_asid_link); |
| spinlock_lock(&as->lock); |
| |
| /* |
| * Steal the ASID. |
| * Note that the stolen ASID is not active. |
| */ |
| asid = as->asid; |
| ASSERT(asid != ASID_INVALID); |
| |
| /* |
| * Get the system rid of the stolen ASID. |
| */ |
| tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0); |
| tlb_shootdown_finalize(); |
| as->asid = ASID_INVALID; |
| |
| spinlock_unlock(&as->lock); |
| } else { |
| |
| /* |
| * There is at least one unallocated ASID. |
| * Find it and assign it. |
| */ |
| |
| asid = asid_find_free(); |
| asids_allocated++; |
| } |
| |
| spinlock_unlock(&asidlock); |
| interrupts_restore(ipl); |
| |
| return asid; |
| } |
| |
| /** Release address space identifier. |
| * |
| * This code relies on architecture |
| * dependent functionality. |
| * |
| * @param asid ASID to be released. |
| */ |
| void asid_put(asid_t asid) |
| { |
| ipl_t ipl; |
| |
| ipl = interrupts_disable(); |
| spinlock_lock(&asidlock); |
| |
| asids_allocated--; |
| asid_put_arch(asid); |
| |
| spinlock_unlock(&asidlock); |
| interrupts_restore(ipl); |
| } |
| |
| /** Install ASID. |
| * |
| * This function is to be executed on each address space switch. |
| * |
| * @param as Address space. |
| */ |
| void asid_install(as_t *as) |
| { |
| ipl_t ipl; |
| |
| ipl = interrupts_disable(); |
| spinlock_lock(&asidlock); |
| spinlock_lock(&as->lock); |
| |
| if (as->asid != ASID_KERNEL) { |
| if (as->asid != ASID_INVALID) { |
| /* |
| * This address space has valid ASID. |
| * Remove 'as' from the list of address spaces |
| * with assigned ASID, so that it can be later |
| * appended to the tail of the same list. |
| * This is to prevent stealing of ASIDs from |
| * recently installed address spaces. |
| */ |
| list_remove(&as->as_with_asid_link); |
| } else { |
| spinlock_unlock(&as->lock); |
| spinlock_unlock(&asidlock); |
| |
| /* |
| * This address space doesn't have ASID assigned. |
| * It was stolen or the address space is being |
| * installed for the first time. |
| * Allocate new ASID for it. |
| */ |
| as->asid = asid_get(); |
| spinlock_lock(&asidlock); |
| spinlock_lock(&as->lock); |
| } |
| |
| /* |
| * Now it is sure that 'as' has ASID. |
| * It is therefore appended to the list |
| * of address spaces from which it can |
| * be stolen. |
| */ |
| list_append(&as->as_with_asid_link, &as_with_asid_head); |
| } |
| |
| spinlock_unlock(&as->lock); |
| spinlock_unlock(&asidlock); |
| interrupts_restore(ipl); |
| } |