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 <andreas.sandberg@arm.com>
Reviewed-by: Curtis Dunham <curtis.dunham@arm.com>
Reviewed-by: Alexandru Dutu <alexandru.dutu@amd.com>

1 files changed, 7 insertions, 0 deletions

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) {