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accel/tcg: Remove CF_LAST_IO

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In cpu_exec_step_atomic, we did not set CF_LAST_IO, which lead
to a loop with cpu_io_recompile.

But since 18a536f1f8 ("Always require can_do_io") we no longer
need a flag to indicate when the last insn should have can_do_io set,
so remove the flag entirely.

Reported-by: Clément Chigot <chigot@adacore.com>
Tested-by: Clément Chigot <chigot@adacore.com>
Reviewed-by: Claudio Fontana <cfontana@suse.de>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1961
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2023-11-10 08:21:23 -08:00
parent 6d44474b3b
commit cf9b5790db
7 changed files with 22 additions and 37 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
accel/tcg/cpu-exec.c
View file

@ -721,7 +721,7 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
&& cpu->neg.icount_decr.u16.low + cpu->icount_extra == 0) {
/* Execute just one insn to trigger exception pending in the log */
cpu->cflags_next_tb = (curr_cflags(cpu) & ~CF_USE_ICOUNT)
| CF_LAST_IO | CF_NOIRQ | 1;
| CF_NOIRQ | 1;
}
#endif
return false;

6
accel/tcg/tb-maint.c
View file

@ -1083,8 +1083,7 @@ bool tb_invalidate_phys_page_unwind(tb_page_addr_t addr, uintptr_t pc)
if (current_tb_modified) {
/* Force execution of one insn next time. */
CPUState *cpu = current_cpu;
cpu->cflags_next_tb =
1 | CF_LAST_IO | CF_NOIRQ | curr_cflags(current_cpu);
cpu->cflags_next_tb = 1 | CF_NOIRQ | curr_cflags(current_cpu);
return true;
}
return false;
@ -1154,8 +1153,7 @@ tb_invalidate_phys_page_range__locked(struct page_collection *pages,
if (current_tb_modified) {
page_collection_unlock(pages);
/* Force execution of one insn next time. */
current_cpu->cflags_next_tb =
1 | CF_LAST_IO | CF_NOIRQ | curr_cflags(current_cpu);
current_cpu->cflags_next_tb = 1 | CF_NOIRQ | curr_cflags(current_cpu);
mmap_unlock();
cpu_loop_exit_noexc(current_cpu);
}

4
accel/tcg/translate-all.c
View file

@ -304,7 +304,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
if (phys_pc == -1) {
/* Generate a one-shot TB with 1 insn in it */
cflags = (cflags & ~CF_COUNT_MASK) | CF_LAST_IO | 1;
cflags = (cflags & ~CF_COUNT_MASK) | 1;
}
max_insns = cflags & CF_COUNT_MASK;
@ -632,7 +632,7 @@ void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr)
* operations only (which execute after completion) so we don't
* double instrument the instruction.
*/
cpu->cflags_next_tb = curr_cflags(cpu) | CF_MEMI_ONLY | CF_LAST_IO | n;
cpu->cflags_next_tb = curr_cflags(cpu) | CF_MEMI_ONLY | n;
if (qemu_loglevel_mask(CPU_LOG_EXEC)) {
vaddr pc = log_pc(cpu, tb);

22
accel/tcg/translator.c
View file

@ -89,7 +89,7 @@ static TCGOp *gen_tb_start(DisasContextBase *db, uint32_t cflags)
* each translation block. The cost is minimal, plus it would be
* very easy to forget doing it in the translator.
*/
set_can_do_io(db, db->max_insns == 1 && (cflags & CF_LAST_IO));
set_can_do_io(db, db->max_insns == 1);
return icount_start_insn;
}
@ -151,13 +151,7 @@ void translator_loop(CPUState *cpu, TranslationBlock *tb, int *max_insns,
ops->tb_start(db, cpu);
tcg_debug_assert(db->is_jmp == DISAS_NEXT); /* no early exit */
if (cflags & CF_MEMI_ONLY) {
/* We should only see CF_MEMI_ONLY for io_recompile. */
assert(cflags & CF_LAST_IO);
plugin_enabled = plugin_gen_tb_start(cpu, db, true);
} else {
plugin_enabled = plugin_gen_tb_start(cpu, db, false);
}
plugin_enabled = plugin_gen_tb_start(cpu, db, cflags & CF_MEMI_ONLY);
db->plugin_enabled = plugin_enabled;
while (true) {
@ -169,11 +163,13 @@ void translator_loop(CPUState *cpu, TranslationBlock *tb, int *max_insns,
plugin_gen_insn_start(cpu, db);
}
/* Disassemble one instruction. The translate_insn hook should
update db->pc_next and db->is_jmp to indicate what should be
done next -- either exiting this loop or locate the start of
the next instruction. */
if (db->num_insns == db->max_insns && (cflags & CF_LAST_IO)) {
/*
* Disassemble one instruction. The translate_insn hook should
* update db->pc_next and db->is_jmp to indicate what should be
* done next -- either exiting this loop or locate the start of
* the next instruction.
*/
if (db->num_insns == db->max_insns) {
/* Accept I/O on the last instruction. */
set_can_do_io(db, true);
}

6
docs/devel/tcg-icount.rst
View file

@ -62,12 +62,6 @@ To deal with this case, when an I/O access is made we:
- re-compile a single [1]_ instruction block for the current PC
- exit the cpu loop and execute the re-compiled block
The new block is created with the CF_LAST_IO compile flag which
ensures the final instruction translation starts with a call to
gen_io_start() so we don't enter a perpetual loop constantly
recompiling a single instruction block. For translators using the
common translator_loop this is done automatically.
.. [1] sometimes two instructions if dealing with delay slots
Other I/O operations

13
include/exec/translation-block.h
View file

@ -71,13 +71,12 @@ struct TranslationBlock {
#define CF_NO_GOTO_TB 0x00000200 /* Do not chain with goto_tb */
#define CF_NO_GOTO_PTR 0x00000400 /* Do not chain with goto_ptr */
#define CF_SINGLE_STEP 0x00000800 /* gdbstub single-step in effect */
#define CF_LAST_IO 0x00008000 /* Last insn may be an IO access. */
#define CF_MEMI_ONLY 0x00010000 /* Only instrument memory ops */
#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_PCREL 0x00200000 /* Opcodes in TB are PC-relative */
#define CF_MEMI_ONLY 0x00001000 /* Only instrument memory ops */
#define CF_USE_ICOUNT 0x00002000
#define CF_INVALID 0x00004000 /* TB is stale. Set with @jmp_lock held */
#define CF_PARALLEL 0x00008000 /* Generate code for a parallel context */
#define CF_NOIRQ 0x00010000 /* Generate an uninterruptible TB */
#define CF_PCREL 0x00020000 /* Opcodes in TB are PC-relative */
#define CF_CLUSTER_MASK 0xff000000 /* Top 8 bits are cluster ID */
#define CF_CLUSTER_SHIFT 24

6
system/watchpoint.c
View file

@ -179,8 +179,7 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
*/
if (!cpu->neg.can_do_io) {
/* Force execution of one insn next time. */
cpu->cflags_next_tb = 1 | CF_LAST_IO | CF_NOIRQ
| curr_cflags(cpu);
cpu->cflags_next_tb = 1 | CF_NOIRQ | curr_cflags(cpu);
cpu_loop_exit_restore(cpu, ra);
}
/*
@ -212,8 +211,7 @@ void cpu_check_watchpoint(CPUState *cpu, vaddr addr, vaddr len,
cpu_loop_exit(cpu);
} else {
/* Force execution of one insn next time. */
cpu->cflags_next_tb = 1 | CF_LAST_IO | CF_NOIRQ
| curr_cflags(cpu);
cpu->cflags_next_tb = 1 | CF_NOIRQ | curr_cflags(cpu);
mmap_unlock();
cpu_loop_exit_noexc(cpu);
}