accel/tcg: Improve tb_flush usage

[PATCH 02/11] accel/tcg: Split out tb_flush__exclusive

Richard Henderson posted 11 patches 9 hours ago

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Maintainers: Richard Henderson <richard.henderson@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, "Alex Bennée" <alex.bennee@linaro.org>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Eduardo Habkost <eduardo@habkost.net>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Yanan Wang <wangyanan55@huawei.com>, Zhao Liu <zhao1.liu@intel.com>, Nicholas Piggin <npiggin@gmail.com>, Harsh Prateek Bora <harshpb@linux.ibm.com>, Laurent Vivier <laurent@vivier.eu>, Alexandre Iooss <erdnaxe@crans.org>, Mahmoud Mandour <ma.mandourr@gmail.com>, Pierrick Bouvier <pierrick.bouvier@linaro.org>, Palmer Dabbelt <palmer@dabbelt.com>, Alistair Francis <alistair.francis@wdc.com>, Weiwei Li <liwei1518@gmail.com>, Daniel Henrique Barboza <dbarboza@ventanamicro.com>, Liu Zhiwei <zhiwei_liu@linux.alibaba.com>

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[PATCH 02/11] accel/tcg: Split out tb_flush__exclusive

Posted by Richard Henderson 9 hours ago

Expose a routine to be called when no cpus are running.
Simplify the do_tb_flush run_on_cpu callback, because
that is explicitly called with start_exclusive; there
is no need for the mmap_lock as well.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/tb-flush.h |  1 +
 accel/tcg/tb-maint.c    | 28 ++++++++++++++--------------
 2 files changed, 15 insertions(+), 14 deletions(-)

diff --git a/include/exec/tb-flush.h b/include/exec/tb-flush.h
index 142c240d94..f3898d1826 100644
--- a/include/exec/tb-flush.h
+++ b/include/exec/tb-flush.h
@@ -23,6 +23,7 @@
  */
 void tb_flush(CPUState *cs);
 
+void tb_flush__exclusive(void);
 void tcg_flush_jmp_cache(CPUState *cs);
 
 #endif /* _TB_FLUSH_H_ */
diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
index 0048316f99..d1695be00b 100644
--- a/accel/tcg/tb-maint.c
+++ b/accel/tcg/tb-maint.c
@@ -756,17 +756,14 @@ static void tb_remove(TranslationBlock *tb)
 }
 #endif /* CONFIG_USER_ONLY */
 
-/* flush all the translation blocks */
-static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
+/*
+ * Flush all the translation blocks.
+ * Must be called from a context in which no cpus are running,
+ * e.g. start_exclusive() or vm_stop().
+ */
+void tb_flush__exclusive(void)
 {
-    bool did_flush = false;
-
-    mmap_lock();
-    /* If it is already been done on request of another CPU, just retry. */
-    if (tb_ctx.tb_flush_count != tb_flush_count.host_int) {
-        goto done;
-    }
-    did_flush = true;
+    CPUState *cpu;
 
     CPU_FOREACH(cpu) {
         tcg_flush_jmp_cache(cpu);
@@ -778,11 +775,14 @@ static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
     tcg_region_reset_all();
     /* XXX: flush processor icache at this point if cache flush is expensive */
     qatomic_inc(&tb_ctx.tb_flush_count);
+    qemu_plugin_flush_cb();
+}
 
-done:
-    mmap_unlock();
-    if (did_flush) {
-        qemu_plugin_flush_cb();
+static void do_tb_flush(CPUState *cpu, run_on_cpu_data tb_flush_count)
+{
+    /* If it is already been done on request of another CPU, just retry. */
+    if (tb_ctx.tb_flush_count == tb_flush_count.host_int) {
+        tb_flush__exclusive();
     }
 }
 
-- 
2.43.0

Re: [PATCH 02/11] accel/tcg: Split out tb_flush__exclusive

Posted by Pierrick Bouvier 8 hours ago

On 2025-09-06 07:18, Richard Henderson wrote:
> Expose a routine to be called when no cpus are running.
> Simplify the do_tb_flush run_on_cpu callback, because
> that is explicitly called with start_exclusive; there
> is no need for the mmap_lock as well.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   include/exec/tb-flush.h |  1 +
>   accel/tcg/tb-maint.c    | 28 ++++++++++++++--------------
>   2 files changed, 15 insertions(+), 14 deletions(-)

Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>