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accel/tcg: allow plugin instrumentation to be disable via cflags

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When icount is enabled and we recompile an MMIO access we end up
double counting the instruction execution. To avoid this we introduce
the CF_MEMI cflag which only allows memory instrumentation for the
next TB (which won't yet have been counted). As this is part of the
hashed compile flags we will only execute the generated TB while
coming out of a cpu_io_recompile.

While we are at it delete the old TODO. We might as well keep the
translation handy as it's likely you will repeatedly hit it on each
MMIO access.

Reported-by: Aaron Lindsay <aaron@os.amperecomputing.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Aaron Lindsay <aaron@os.amperecomputing.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210213130325.14781-21-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2021-02-13 13:03:22 +00:00
parent c4afb3456c
commit cfd405eae6
7 changed files with 49 additions and 27 deletions
Download patch file Download diff file Expand all files Collapse all files

5
accel/tcg/translator.c
View file

@ -58,7 +58,8 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db,
ops->tb_start(db, cpu);
tcg_debug_assert(db->is_jmp == DISAS_NEXT); /* no early exit */
plugin_enabled = plugin_gen_tb_start(cpu, tb);
plugin_enabled = plugin_gen_tb_start(cpu, tb,
tb_cflags(db->tb) & CF_MEMI_ONLY);
while (true) {
db->num_insns++;
@ -100,6 +101,8 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db,
gen_io_start();
ops->translate_insn(db, cpu);
} else {
/* we should only see CF_MEMI_ONLY for io_recompile */
tcg_debug_assert(!(tb_cflags(db->tb) & CF_MEMI_ONLY));
ops->translate_insn(db, cpu);
}