From: Andrew Bardsley <Andrew.Bardsley@arm.com>
Date: Tue, 2 Dec 2014 11:08:11 +0000 (-0500)
Subject: arm: Fix TLB ignoring faults when table walking
X-Git-Tag: stable_2015_04_15~88
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=3cd0b1f6a6873ef06351dd49f3c7697175303371;p=gem5.git

arm: Fix TLB ignoring faults when table walking

This patch fixes a case where the Minor CPU can deadlock due to the lack
of a response to TLB request because of a bug in fault handling in the ARM
table walker.

TableWalker::processWalkWrapper is the scheduler-called wrapper which
handles deferred walks which calls to TableWalker::wait cannot immediately
process.  The handling of faults generated by processWalk{AArch64,LPAE,}
calls in those two functions is is different.  processWalkWrapper ignores
fault returns from processWalk... which can lead to ::finish not being
called on a translation.

This fix provides fault handling in processWalkWrapper similar to that
found in the leaf functions which BaseTLB::Translation::finish.
---

diff --git a/src/arch/arm/table_walker.cc b/src/arch/arm/table_walker.cc
index 30fdf9811..6a0f0144a 100644
--- a/src/arch/arm/table_walker.cc
+++ b/src/arch/arm/table_walker.cc
@@ -344,12 +344,22 @@ TableWalker::processWalkWrapper()
         // We've got a valid request, lets process it
         pending = true;
         pendingQueue.pop_front();
+        // Keep currState in case one of the processWalk... calls NULLs it
+        WalkerState *curr_state_copy = currState;
+        Fault f;
         if (currState->aarch64)
-            processWalkAArch64();
+            f = processWalkAArch64();
         else if ((_haveLPAE && currState->ttbcr.eae) || currState->isHyp || isStage2)
-            processWalkLPAE();
+            f = processWalkLPAE();
         else
-            processWalk();
+            f = processWalk();
+
+        if (f != NoFault) {
+            curr_state_copy->transState->finish(f, curr_state_copy->req,
+                    curr_state_copy->tc, curr_state_copy->mode);
+
+            delete curr_state_copy;
+        }
         return;
     }