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tcg: Restart after TB code generation overflow

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If a TB generates too much code, try again with fewer insns.

Fixes: https://bugs.launchpad.net/bugs/1824853
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2019-04-15 22:06:39 -10:00
parent 8b86d6d258
commit 6e6c4efed9
2 changed files with 36 additions and 6 deletions
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38
accel/tcg/translate-all.c
View File

@ -1722,6 +1722,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
tb->cflags = cflags;
tb->trace_vcpu_dstate = *cpu->trace_dstate;
tcg_ctx->tb_cflags = cflags;
tb_overflow:
#ifdef CONFIG_PROFILER
/* includes aborted translations because of exceptions */
@ -1755,14 +1756,39 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
ti = profile_getclock();
#endif
/* ??? Overflow could be handled better here. In particular, we
don't need to re-do gen_intermediate_code, nor should we re-do
the tcg optimization currently hidden inside tcg_gen_code. All
that should be required is to flush the TBs, allocate a new TB,
re-initialize it per above, and re-do the actual code generation. */
gen_code_size = tcg_gen_code(tcg_ctx, tb);
if (unlikely(gen_code_size < 0)) {
goto buffer_overflow;
switch (gen_code_size) {
case -1:
/*
* Overflow of code_gen_buffer, or the current slice of it.
*
* TODO: We don't need to re-do gen_intermediate_code, nor
* should we re-do the tcg optimization currently hidden
* inside tcg_gen_code. All that should be required is to
* flush the TBs, allocate a new TB, re-initialize it per
* above, and re-do the actual code generation.
*/
goto buffer_overflow;
case -2:
/*
* The code generated for the TranslationBlock is too large.
* The maximum size allowed by the unwind info is 64k.
* There may be stricter constraints from relocations
* in the tcg backend.
*
* Try again with half as many insns as we attempted this time.
* If a single insn overflows, there's a bug somewhere...
*/
max_insns = tb->icount;
assert(max_insns > 1);
max_insns /= 2;
goto tb_overflow;
default:
g_assert_not_reached();
}
}
search_size = encode_search(tb, (void *)gen_code_buf + gen_code_size);
if (unlikely(search_size < 0)) {

4
tcg/tcg.c
View File

@ -3996,6 +3996,10 @@ int tcg_gen_code(TCGContext *s, TranslationBlock *tb)
if (unlikely((void *)s->code_ptr > s->code_gen_highwater)) {
return -1;
}
/* Test for TB overflow, as seen by gen_insn_end_off. */
if (unlikely(tcg_current_code_size(s) > UINT16_MAX)) {
return -2;
}
}
tcg_debug_assert(num_insns >= 0);
s->gen_insn_end_off[num_insns] = tcg_current_code_size(s);