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| /gem5/src/cpu/simple/ | ||
| H A D | atomic.hh | diff 9443:0cb3209bc5c7 Mon Jan 07 13:05:00 EST 2013 Andreas Sandberg <Andreas.Sandberg@ARM.com> cpu: Make sure that a drained atomic CPU isn't executing ucode Currently, the atomic CPU can be in the middle of a microcode sequence when it is drained. This leads to two problems: * When switching to a hardware virtualized CPU, we obviously can't execute gem5 microcode. * Since curMacroStaticInst is populated when executing microcode, repeated switching between CPUs executing microcode leads to incorrect execution. After applying this patch, the CPU will be on a proper instruction boundary, which means that it is safe to switch to any CPU model (including hardware virtualized ones). This changeset fixes a bug where the multiple switches to the same atomic CPU sometimes corrupts the target state because of dangling pointers to the currently executing microinstruction. Note: This changeset moves tick event descheduling from switchOut() to drain(), which makes timing consistent between just draining a system and draining /and/ switching between two atomic CPUs. This makes debugging quite a lot easier (execution traces get the same timing), but the latency of the last instruction before a drain will not be accounted for correctly (it will always be 1 cycle). Note 2: This changeset removes so_state variable, the locked variable, and the tickEvent from checkpoints since none of them contain state that needs to be preserved across checkpoints. The so_state is made redundant because we don't use the drain state variable anymore, the lock variable should never be set when the system is drained, and the tick event isn't scheduled. |
| H A D | atomic.cc | diff 9443:0cb3209bc5c7 Mon Jan 07 13:05:00 EST 2013 Andreas Sandberg <Andreas.Sandberg@ARM.com> cpu: Make sure that a drained atomic CPU isn't executing ucode Currently, the atomic CPU can be in the middle of a microcode sequence when it is drained. This leads to two problems: * When switching to a hardware virtualized CPU, we obviously can't execute gem5 microcode. * Since curMacroStaticInst is populated when executing microcode, repeated switching between CPUs executing microcode leads to incorrect execution. After applying this patch, the CPU will be on a proper instruction boundary, which means that it is safe to switch to any CPU model (including hardware virtualized ones). This changeset fixes a bug where the multiple switches to the same atomic CPU sometimes corrupts the target state because of dangling pointers to the currently executing microinstruction. Note: This changeset moves tick event descheduling from switchOut() to drain(), which makes timing consistent between just draining a system and draining /and/ switching between two atomic CPUs. This makes debugging quite a lot easier (execution traces get the same timing), but the latency of the last instruction before a drain will not be accounted for correctly (it will always be 1 cycle). Note 2: This changeset removes so_state variable, the locked variable, and the tickEvent from checkpoints since none of them contain state that needs to be preserved across checkpoints. The so_state is made redundant because we don't use the drain state variable anymore, the lock variable should never be set when the system is drained, and the tick event isn't scheduled. |
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