docs/devel/tcg.rst

14 Generator". For more information, please take a look at :ref:`tcg-ops-ref`.
20 -----------------------
34 ---------------------
48 callback to be re-evaluated before executing additional instructions.
81    data. The information updated in this step must be inferable from both
87 Step 1, ``tcg_gen_goto_tb()``, will emit a ``goto_tb`` TCG
90 of step 2's instructions, which update the CPU state information. Step 3,
95 The first time this whole sequence is executed, step 1 simply jumps
96 to step 2. Then the CPU state information gets updated and we exit from
108 ``goto_tb`` step, it will already be patched (assuming the destination TB
121 Note that, on step 3 (``tcg_gen_exit_tb()``), in addition to the
127 Self-modifying code and translated code invalidation
128 ----------------------------------------------------
130 Self-modifying code is a special challenge in x86 emulation because no
134 User-mode emulation marks a host page as write-protected (if it is
135 not already read-only) every time translated code is generated for a
152 -----------------
159 target program counter, and looks up where the exception happened
165 very often throughout the execution of a translation block---this includes
168 looked up on exceptions.
171 -------------
177 QEMU uses an address translation cache (TLB) to speed up the translation.
194 ---------------------
199 limitation you can use the ``-perfmap`` or the ``-jitdump`` option to generate
200 map files. ``-perfmap`` is lightweight and produces only guest-host mappings.
201 ``-jitdump`` additionally saves JITed code and guest debug information (if
207   perf record $QEMU -perfmap $REMAINING_ARGS
210   perf record -k 1 $QEMU -jitdump $REMAINING_ARGS
211   DEBUGINFOD_URLS= perf inject -j -i perf.data -o perf.data.jitted
212   perf report -i perf.data.jitted
214 Note that qemu-system generates mappings only for ``-kernel`` files in ELF