changeset b58c5c5854de in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=b58c5c5854de
description:
arm: Handle functional TLB walks properly
The table walker code currently accounts for two types of walks,
Atomic and Timing, and treats them differently. Atomic walks keep a
single instance of WalkerState around for all walks to use in
currState. Timing mode keeps a queue of in-flight WalkerStates and
maintains currState as NULL between walks.
If a functional walk is done during Timing mode, it is treated as an
atomic walk and either creates a persistent WalkerState if in between
Timing walks, or stomps an existing currState for an in-progress
Timing walk.
This patch distinguishes functional walks as being able to exist at
any time and sets up a temporary WalkerState for its exclusive use and
then cleans up when finished, leaving any in progress Atomic or Timing
walks undisturbed.
diffstat:
src/arch/arm/table_walker.cc | 26 ++++++++++++++++++++++----
1 files changed, 22 insertions(+), 4 deletions(-)
diffs (54 lines):
diff -r 83bb6e381cbf -r b58c5c5854de src/arch/arm/table_walker.cc
--- a/src/arch/arm/table_walker.cc Fri Mar 07 15:56:23 2014 -0500
+++ b/src/arch/arm/table_walker.cc Fri Mar 07 15:56:23 2014 -0500
@@ -160,8 +160,9 @@
bool secure, TLB::ArmTranslationType tranType)
{
assert(!(_functional && _timing));
+ WalkerState *savedCurrState = NULL;
- if (!currState) {
+ if (!currState && !_functional) {
// For atomic mode, a new WalkerState instance should be only created
// once per TLB. For timing mode, a new instance is generated for every
// TLB miss.
@@ -169,6 +170,14 @@
currState = new WalkerState();
currState->tableWalker = this;
+ } else if (_functional) {
+ // If we are mixing functional mode with timing (or even
+ // atomic), we need to to be careful and clean up after
+ // ourselves to not risk getting into an inconsistent state.
+ DPRINTF(TLBVerbose, "creating functional instance of WalkerState\n");
+ savedCurrState = currState;
+ currState = new WalkerState();
+ currState->tableWalker = this;
} else if (_timing) {
// This is a translation that was completed and then faulted again
// because some underlying parameters that affect the translation
@@ -264,12 +273,21 @@
}
if (!currState->timing) {
+ Fault fault = NoFault;
if (currState->aarch64)
- return processWalkAArch64();
+ fault = processWalkAArch64();
else if (long_desc_format)
- return processWalkLPAE();
+ fault = processWalkLPAE();
else
- return processWalk();
+ fault = processWalk();
+
+ // If this was a functional non-timing access restore state to
+ // how we found it.
+ if (currState->functional) {
+ delete currState;
+ currState = savedCurrState;
+ }
+ return fault;
}
if (pending || pendingQueue.size()) {
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