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plugins: fix optimization in plugin_gen_disable_mem_helpers

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We were mistakenly checking tcg_ctx->plugin_insn as a canary to know
whether the TB had emitted helpers that might have accessed memory.

The problem is that tcg_ctx->plugin_insn gets updated on every
instruction in the TB, which results in us wrongly performing the
optimization (i.e. not clearing cpu->plugin_mem_cbs) way too often,
since it's not rare that the last instruction in the TB doesn't
use helpers.

Fix it by tracking a per-TB canary.

While at it, expand documentation.

Related: #1381

Signed-off-by: Emilio Cota <cota@braap.org>
Message-Id: <20230108164731.61469-2-cota@braap.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20230124180127.1881110-32-alex.bennee@linaro.org>
This commit is contained in:
Emilio Cota 2023-01-24 18:01:23 +00:00 • committed by Alex Bennée
parent 2bbbc1be8d
commit 3fd62e73ad
2 changed files with 25 additions and 8 deletions
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7
include/qemu/plugin.h
View file

@ -118,7 +118,10 @@ struct qemu_plugin_insn {
void *haddr;
GArray *cbs[PLUGIN_N_CB_TYPES][PLUGIN_N_CB_SUBTYPES];
bool calls_helpers;
/* if set, the instruction calls helpers that might access guest memory */
bool mem_helper;
bool mem_only;
};
@ -158,6 +161,10 @@ struct qemu_plugin_tb {
void *haddr1;
void *haddr2;
bool mem_only;
/* if set, the TB calls helpers that might access guest memory */
bool mem_helper;
GArray *cbs[PLUGIN_N_CB_SUBTYPES];
};