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mem: Ignore uncacheable MSHRs when finding matches

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This patch changes how we search for matching MSHRs, ignoring any MSHR
that is allocated for an uncacheable access. By doing so, this patch
fixes a corner case in the MSHRs where incorrect data ended up being
copied into a (cacheable) read packet due to a first uncacheable MSHR
target of size 4, followed by a cacheable target to the same MSHR of
size 64. The latter target was filled with nonsense data.
This commit is contained in:
Andreas Hansson 2015-03-27 04:56:00 -04:00
parent 801ce65eae
commit a7a1e6004a
2 changed files with 18 additions and 7 deletions
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14
src/mem/cache/mshr.cc vendored
View file

@ -273,6 +273,15 @@ MSHR::deallocate()
void
MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order)
{
// assume we'd never issue a prefetch when we've got an
// outstanding miss
assert(pkt->cmd != MemCmd::HardPFReq);
// uncacheable accesses always allocate a new MSHR, and cacheable
// accesses ignore any uncacheable MSHRs, thus we should never
// have targets addded if originally allocated uncacheable
assert(!_isUncacheable);
// if there's a request already in service for this MSHR, we will
// have to defer the new target until after the response if any of
// the following are true:
@ -283,11 +292,6 @@ MSHR::allocateTarget(PacketPtr pkt, Tick whenReady, Counter _order)
// getting an exclusive block back or we have already snooped
// another read request that will downgrade our exclusive block
// to shared
// assume we'd never issue a prefetch when we've got an
// outstanding miss
assert(pkt->cmd != MemCmd::HardPFReq);
if (inService &&
(!deferredTargets.empty() || hasPostInvalidate() ||
(pkt->needsExclusive() &&

11
src/mem/cache/mshr_queue.cc vendored
View file

@ -69,7 +69,13 @@ MSHR *
MSHRQueue::findMatch(Addr blk_addr, bool is_secure) const
{
for (const auto& mshr : allocatedList) {
if (mshr->blkAddr == blk_addr && mshr->isSecure == is_secure) {
// we ignore any MSHRs allocated for uncacheable accesses and
// simply ignore them when matching, in the cache we never
// check for matches when adding new uncacheable entries, and
// we do not want normal cacheable accesses being added to an
// MSHR serving an uncacheable access
if (!mshr->isUncacheable() && mshr->blkAddr == blk_addr &&
mshr->isSecure == is_secure) {
return mshr;
}
}
@ -84,7 +90,8 @@ MSHRQueue::findMatches(Addr blk_addr, bool is_secure,
assert(matches.empty());
bool retval = false;
for (const auto& mshr : allocatedList) {
if (mshr->blkAddr == blk_addr && mshr->isSecure == is_secure) {
if (!mshr->isUncacheable() && mshr->blkAddr == blk_addr &&
mshr->isSecure == is_secure) {
retval = true;
matches.push_back(mshr);
}