From e2507407b17188dca802082434cfe0230d9bfa61 Mon Sep 17 00:00:00 2001 From: Giacomo Gabrielli Date: Fri, 11 Feb 2011 18:29:35 -0600 Subject: O3: Enhance data address translation by supporting hardware page table walkers. Some ISAs (like ARM) relies on hardware page table walkers. For those ISAs, when a TLB miss occurs, initiateTranslation() can return with NoFault but with the translation unfinished. Instructions experiencing a delayed translation due to a hardware page table walk are deferred until the translation completes and kept into the IQ. In order to keep track of them, the IQ has been augmented with a queue of the outstanding delayed memory instructions. When their translation completes, instructions are re-executed (only their initiateAccess() was already executed; their DTB translation is now skipped). The IEW stage has been modified to support such a 2-pass execution. --- src/cpu/o3/inst_queue.hh | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'src/cpu/o3/inst_queue.hh') diff --git a/src/cpu/o3/inst_queue.hh b/src/cpu/o3/inst_queue.hh index be936e204..64df35743 100644 --- a/src/cpu/o3/inst_queue.hh +++ b/src/cpu/o3/inst_queue.hh @@ -1,4 +1,16 @@ /* + * Copyright (c) 2011 ARM Limited + * All rights reserved. + * + * The license below extends only to copyright in the software and shall + * not be construed as granting a license to any other intellectual + * property including but not limited to intellectual property relating + * to a hardware implementation of the functionality of the software + * licensed hereunder. You may use the software subject to the license + * terms below provided that you ensure that this notice is replicated + * unmodified and in its entirety in all distributions of the software, + * modified or unmodified, in source code or in binary form. + * * Copyright (c) 2004-2006 The Regents of The University of Michigan * All rights reserved. * @@ -180,6 +192,11 @@ class InstructionQueue */ DynInstPtr getInstToExecute(); + /** Returns a memory instruction that was referred due to a delayed DTB + * translation if it is now ready to execute. + */ + DynInstPtr getDeferredMemInstToExecute(); + /** * Records the instruction as the producer of a register without * adding it to the rest of the IQ. @@ -223,6 +240,12 @@ class InstructionQueue /** Completes a memory operation. */ void completeMemInst(DynInstPtr &completed_inst); + /** + * Defers a memory instruction when its DTB translation incurs a hw + * page table walk. + */ + void deferMemInst(DynInstPtr &deferred_inst); + /** Indicates an ordering violation between a store and a load. */ void violation(DynInstPtr &store, DynInstPtr &faulting_load); @@ -284,6 +307,11 @@ class InstructionQueue /** List of instructions that are ready to be executed. */ std::list instsToExecute; + /** List of instructions waiting for their DTB translation to + * complete (hw page table walk in progress). + */ + std::list deferredMemInsts; + /** * Struct for comparing entries to be added to the priority queue. * This gives reverse ordering to the instructions in terms of -- cgit v1.2.3