From a3efb6bd1d0d83297b5b412badc0b7db98b7be1e Mon Sep 17 00:00:00 2001 From: Andreas Sandberg Date: Wed, 30 Mar 2016 10:52:25 +0100 Subject: [PATCH] kvm: Add an option to force context sync on kvm entry/exit This changeset adds an option to force the kvm-based CPUs to always synchronize the gem5 thread context representation on entry/exit into the kernel. This is very useful for debugging. Unfortunately, it is also the only way to get reliable register contents when using remote gdb functionality. The long-term solution for the latter would be to implement a kvm-specific thread context. Signed-off-by: Andreas Sandberg Reviewed-by: Curtis Dunham Reviewed-by: Alexandru Dutu --- src/cpu/kvm/BaseKvmCPU.py | 2 ++ src/cpu/kvm/base.cc | 7 +++++++ src/cpu/kvm/base.hh | 6 ++++++ 3 files changed, 15 insertions(+) diff --git a/src/cpu/kvm/BaseKvmCPU.py b/src/cpu/kvm/BaseKvmCPU.py index b7c964669..34ab752de 100644 --- a/src/cpu/kvm/BaseKvmCPU.py +++ b/src/cpu/kvm/BaseKvmCPU.py @@ -71,6 +71,8 @@ class BaseKvmCPU(BaseCPU): kvmVM = Param.KvmVM(Parent.any, 'KVM VM (i.e., shared memory domain)') useCoalescedMMIO = Param.Bool(False, "Use coalesced MMIO (EXPERIMENTAL)") usePerfOverflow = Param.Bool(False, "Use perf event overflow counters (EXPERIMENTAL)") + alwaysSyncTC = Param.Bool(False, + "Always sync thread contexts on entry/exit") hostFreq = Param.Clock("2GHz", "Host clock frequency") hostFactor = Param.Float(1.0, "Cycle scale factor") diff --git a/src/cpu/kvm/base.cc b/src/cpu/kvm/base.cc index ea0f494e3..bf4d68603 100644 --- a/src/cpu/kvm/base.cc +++ b/src/cpu/kvm/base.cc @@ -69,6 +69,7 @@ BaseKvmCPU::BaseKvmCPU(BaseKvmCPUParams *params) _status(Idle), dataPort(name() + ".dcache_port", this), instPort(name() + ".icache_port", this), + alwaysSyncTC(params->alwaysSyncTC), threadContextDirty(true), kvmStateDirty(false), vcpuID(vm.allocVCPUID()), vcpuFD(-1), vcpuMMapSize(0), @@ -557,6 +558,9 @@ BaseKvmCPU::tick() nextInstEvent > ctrInsts ? curEventQueue()->nextTick() - curTick() : 0); + if (alwaysSyncTC) + threadContextDirty = true; + // We might need to update the KVM state. syncKvmState(); @@ -588,6 +592,9 @@ BaseKvmCPU::tick() // dirty with respect to the cached thread context. kvmStateDirty = true; + if (alwaysSyncTC) + syncThreadContext(); + // Enter into the RunningService state unless the // simulation was stopped by a timer. if (_kvmRun->exit_reason != KVM_EXIT_INTR) { diff --git a/src/cpu/kvm/base.hh b/src/cpu/kvm/base.hh index dd27328be..7ff0cab5c 100644 --- a/src/cpu/kvm/base.hh +++ b/src/cpu/kvm/base.hh @@ -574,6 +574,12 @@ class BaseKvmCPU : public BaseCPU /** Unused dummy port for the instruction interface */ KVMCpuPort instPort; + /** + * Be conservative and always synchronize the thread context on + * KVM entry/exit. + */ + const bool alwaysSyncTC; + /** * Is the gem5 context dirty? Set to true to force an update of * the KVM vCPU state upon the next call to kvmRun().