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accel/tcg: introduce CF_NOIRQ 

Here we introduce a new compiler flag to disable the checking of exit
request (icount_decr.u32). This is useful when we want to ensure the
next block cannot be preempted by an asynchronous event.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20211129140932.4115115-2-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2021-11-29 14:09:25 +00:00
parent e750c10167
commit 48e14066ac
2 changed files with 18 additions and 4 deletions
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1
include/exec/exec-all.h
View File

@ -503,6 +503,7 @@ struct TranslationBlock {
#define CF_USE_ICOUNT 0x00020000
#define CF_INVALID 0x00040000 /* TB is stale. Set with @jmp_lock held */
#define CF_PARALLEL 0x00080000 /* Generate code for a parallel context */
#define CF_NOIRQ 0x00100000 /* Generate an uninterruptible TB */
#define CF_CLUSTER_MASK 0xff000000 /* Top 8 bits are cluster ID */
#define CF_CLUSTER_SHIFT 24

21
include/exec/gen-icount.h
View File

@ -21,7 +21,6 @@ static inline void gen_tb_start(const TranslationBlock *tb)
{
TCGv_i32 count;
tcg_ctx->exitreq_label = gen_new_label();
if (tb_cflags(tb) & CF_USE_ICOUNT) {
count = tcg_temp_local_new_i32();
} else {
@ -42,7 +41,19 @@ static inline void gen_tb_start(const TranslationBlock *tb)
icount_start_insn = tcg_last_op();
}
tcg_gen_brcondi_i32(TCG_COND_LT, count, 0, tcg_ctx->exitreq_label);
/*
* Emit the check against icount_decr.u32 to see if we should exit
* unless we suppress the check with CF_NOIRQ. If we are using
* icount and have suppressed interruption the higher level code
* should have ensured we don't run more instructions than the
* budget.
*/
if (tb_cflags(tb) & CF_NOIRQ) {
tcg_ctx->exitreq_label = NULL;
} else {
tcg_ctx->exitreq_label = gen_new_label();
tcg_gen_brcondi_i32(TCG_COND_LT, count, 0, tcg_ctx->exitreq_label);
}
if (tb_cflags(tb) & CF_USE_ICOUNT) {
tcg_gen_st16_i32(count, cpu_env,
@ -74,8 +85,10 @@ static inline void gen_tb_end(const TranslationBlock *tb, int num_insns)
tcgv_i32_arg(tcg_constant_i32(num_insns)));
}
gen_set_label(tcg_ctx->exitreq_label);
tcg_gen_exit_tb(tb, TB_EXIT_REQUESTED);
if (tcg_ctx->exitreq_label) {
gen_set_label(tcg_ctx->exitreq_label);
tcg_gen_exit_tb(tb, TB_EXIT_REQUESTED);
}
}
#endif