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Diffstat (limited to 'docs')
| -rw-r--r-- | docs/devel/tcg-plugins.rst | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/docs/devel/tcg-plugins.rst b/docs/devel/tcg-plugins.rst index 535a74684c..9cc09d8c3d 100644 --- a/docs/devel/tcg-plugins.rst +++ b/docs/devel/tcg-plugins.rst @@ -112,6 +112,55 @@ details are opaque to plugins. The plugin is able to query select details of instructions and system configuration only through the exported *qemu_plugin* functions. +However the following assumptions can be made: + +Translation Blocks +++++++++++++++++++ + +All code will go through a translation phase although not all +translations will be necessarily be executed. You need to instrument +actual executions to track what is happening. + +It is quite normal to see the same address translated multiple times. +If you want to track the code in system emulation you should examine +the underlying physical address (``qemu_plugin_insn_haddr``) to take +into account the effects of virtual memory although if the system does +paging this will change too. + +Not all instructions in a block will always execute so if its +important to track individual instruction execution you need to +instrument them directly. However asynchronous interrupts will not +change control flow mid-block. + +Instructions +++++++++++++ + +Instruction instrumentation runs before the instruction executes. You +can be can be sure the instruction will be dispatched, but you can't +be sure it will complete. Generally this will be because of a +synchronous exception (e.g. SIGILL) triggered by the instruction +attempting to execute. If you want to be sure you will need to +instrument the next instruction as well. See the ``execlog.c`` plugin +for examples of how to track this and finalise details after execution. + +Memory Accesses ++++++++++++++++ + +Memory callbacks are called after a successful load or store. +Unsuccessful operations (i.e. faults) will not be visible to memory +instrumentation although the execution side effects can be observed +(e.g. entering a exception handler). + +System Idle and Resume States ++++++++++++++++++++++++++++++ + +The ``qemu_plugin_register_vcpu_idle_cb`` and +``qemu_plugin_register_vcpu_resume_cb`` functions can be used to track +when CPUs go into and return from sleep states when waiting for +external I/O. Be aware though that these may occur less frequently +than in real HW due to the inefficiencies of emulation giving less +chance for the CPU to idle. + Internals --------- |