accel/tcg: Use one_insn_per_tb global instead of old singlestep global

The only place left that looks at the old 'singlestep' global
variable is the TCG curr_cflags() function.  Replace the old global
with a new 'one_insn_per_tb' which is defined in tcg-all.c and
declared in accel/tcg/internal.h.  This keeps it restricted to the
TCG code, unlike 'singlestep' which was available to every file in
the system and defined in multiple different places for softmmu vs
linux-user vs bsd-user.

While we're making this change, use qatomic_read() and qatomic_set()
on the accesses to the new global, because TCG will read it without
holding a lock.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20230417164041.684562-4-peter.maydell@linaro.org

7 files changed, 7 insertions, 8 deletions

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 8370c92c05..bc0e1c3299 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -159,7 +159,7 @@ uint32_t curr_cflags(CPUState *cpu)
      */
     if (unlikely(cpu->singlestep_enabled)) {
         cflags |= CF_NO_GOTO_TB | CF_NO_GOTO_PTR | CF_SINGLE_STEP | 1;
-    } else if (singlestep) {
+    } else if (qatomic_read(&one_insn_per_tb)) {
         cflags |= CF_NO_GOTO_TB | 1;
     } else if (qemu_loglevel_mask(CPU_LOG_TB_NOCHAIN)) {
         cflags |= CF_NO_GOTO_TB;
diff --git a/accel/tcg/internal.h b/accel/tcg/internal.h
index 96f198b28b..7bb0fdbe14 100644
--- a/accel/tcg/internal.h
+++ b/accel/tcg/internal.h
@@ -67,4 +67,6 @@ static inline target_ulong log_pc(CPUState *cpu, const TranslationBlock *tb)
 extern int64_t max_delay;
 extern int64_t max_advance;
 
+extern bool one_insn_per_tb;
+
 #endif /* ACCEL_TCG_INTERNAL_H */
diff --git a/accel/tcg/tcg-all.c b/accel/tcg/tcg-all.c
index fcf361c8db..a831f8d7c3 100644
--- a/accel/tcg/tcg-all.c
+++ b/accel/tcg/tcg-all.c
@@ -31,6 +31,7 @@
 #include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "qemu/accel.h"
+#include "qemu/atomic.h"
 #include "qapi/qapi-builtin-visit.h"
 #include "qemu/units.h"
 #if !defined(CONFIG_USER_ONLY)
@@ -110,6 +111,7 @@ static void tcg_accel_instance_init(Object *obj)
 }
 
 bool mttcg_enabled;
+bool one_insn_per_tb;
 
 static int tcg_init_machine(MachineState *ms)
 {
@@ -219,8 +221,8 @@ static void tcg_set_one_insn_per_tb(Object *obj, bool value, Error **errp)
 {
     TCGState *s = TCG_STATE(obj);
     s->one_insn_per_tb = value;
-    /* For the moment, set the global also: this changes the behaviour */
-    singlestep = value;
+    /* Set the global also: this changes the behaviour */
+    qatomic_set(&one_insn_per_tb, value);
 }
 
 static int tcg_gdbstub_supported_sstep_flags(void)
diff --git a/bsd-user/main.c b/bsd-user/main.c
index 09b84da190..a9e5a127d3 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -49,7 +49,6 @@
 #include "host-os.h"
 #include "target_arch_cpu.h"
 
-int singlestep;
 static bool opt_one_insn_per_tb;
 uintptr_t guest_base;
 bool have_guest_base;
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 565c2030c1..1be4a3117e 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -163,8 +163,6 @@ int cpu_memory_rw_debug(CPUState *cpu, vaddr addr,
                         void *ptr, size_t len, bool is_write);
 
 /* vl.c */
-extern int singlestep;
-
 void list_cpus(void);
 
 #endif /* CPU_COMMON_H */
diff --git a/linux-user/main.c b/linux-user/main.c
index 489694ad65..c7020b413b 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -68,7 +68,6 @@
 char *exec_path;
 char real_exec_path[PATH_MAX];
 
-int singlestep;
 static bool opt_one_insn_per_tb;
 static const char *argv0;
 static const char *gdbstub;
diff --git a/softmmu/globals.c b/softmmu/globals.c
index 39678aa8c5..e83b5428d1 100644
--- a/softmmu/globals.c
+++ b/softmmu/globals.c
@@ -43,7 +43,6 @@ int vga_interface_type = VGA_NONE;
 bool vga_interface_created;
 Chardev *parallel_hds[MAX_PARALLEL_PORTS];
 int win2k_install_hack;
-int singlestep;
 int fd_bootchk = 1;
 int graphic_rotate;
 QEMUOptionRom option_rom[MAX_OPTION_ROMS];