0,0 → 1,221 |
/* |
* 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); |
} |