From b085db84afcbb4824d34b8755f4c09c1fcfefcee Mon Sep 17 00:00:00 2001 From: Binh Pham Date: Sat, 21 Jun 2014 10:39:44 -0700 Subject: [PATCH] x86: fix table walker assertion In a cycle, we could see a R and W requests corresponding to the same page walk being sent to the memory. During the cycle that assertion happens, we have 2 responses corresponding to the R and W above. We also have a 'read' variable to keep track of the inflight Read request, this gets reset to NULL right after we send out any R request; and gets set to the next R in the page walk when a response comes back. The issue we are seeing here is when we get a response for W request, assert(!read) fires because we got a response for R request right before this, hence we set 'read' to NOT NULL value, pointing to the next R request in the pagewalk! This work was done while Binh was an intern at AMD Research. --- src/arch/x86/pagetable_walker.cc | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/src/arch/x86/pagetable_walker.cc b/src/arch/x86/pagetable_walker.cc index 0c8dcd442..e75f2edc4 100644 --- a/src/arch/x86/pagetable_walker.cc +++ b/src/arch/x86/pagetable_walker.cc @@ -608,9 +608,11 @@ Walker::WalkerState::recvPacket(PacketPtr pkt) assert(pkt->isResponse()); assert(inflight); assert(state == Waiting); - assert(!read); inflight--; if (pkt->isRead()) { + // should not have a pending read it we also had one outstanding + assert(!read); + // @todo someone should pay for this pkt->busFirstWordDelay = pkt->busLastWordDelay = 0; -- 2.30.2