/*
* 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.
*/
/** @addtogroup kernel_genarch_mm
* @{
*/
/**
* @file
* @brief 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.
*
* This code depends on the fact that ASIDS_ALLOCABLE
* is greater than number of supported CPUs (i.e. the
* amount of concurently active address spaces).
*
* Architectures that don't have hardware support for address
* spaces do not compile with this file.
*/
#include <assert.h>
#include <mm/asid.h>
#include <mm/as.h>
#include <mm/tlb.h>
#include <arch/mm/asid.h>
#include <synch/spinlock.h>
#include <synch/mutex.h>
#include <adt/list.h>
static size_t asids_allocated = 0;
/** Allocate free address space identifier.
*
* @return New ASID.
*/
asid_t asid_get(void)
{
asid_t asid;
link_t *tmp;
as_t *as;
assert(interrupts_disabled());
assert(spinlock_locked(&asidlock));
/*
* Check if there is an unallocated ASID.
*/
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 = list_first(&inactive_as_with_asid_list);
assert(tmp != NULL);
list_remove(tmp);
as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
/*
* Steal the ASID.
* Note that the stolen ASID is not active.
*/
asid = as->asid;
assert(asid != ASID_INVALID);
/*
* Notify the address space from wich the ASID
* was stolen by invalidating its asid member.
*/
as->asid = ASID_INVALID;
/*
* If the architecture uses some software cache
* of TLB entries (e.g. TSB on sparc64), the
* cache must be invalidated as well.
*/
as_invalidate_translation_cache(as, 0, (size_t) -1);
/*
* Get the system rid of the stolen ASID.
*/
ipl_t ipl = tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
tlb_invalidate_asid(asid);
tlb_shootdown_finalize(ipl);
} else {
/*
* There is at least one unallocated ASID.
* Find it and assign it.
*/
asid = asid_find_free();
asids_allocated++;
/*
* Purge the allocated ASID from TLBs.
*/
ipl_t ipl = tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
tlb_invalidate_asid(asid);
tlb_shootdown_finalize(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)
{
asids_allocated--;
asid_put_arch(asid);
}
/** @}
*/