PING: [PATCH] monitor: Support specified vCPU registers

[zhenwei pi]

PING!

On 7/19/22 15:55, zhenwei pi wrote:

Originally we have to get all the vCPU registers and parse the
specified one. To improve the performance of this usage, allow user
specified vCPU id to query registers.

Run a VM with 16 vCPU, use bcc tool to track the latency of
'hmp_info_registers':
'info registers -a' uses about 3ms;
'info register 12' uses about 150us.

Signed-off-by: zhenwei pi <pizhen...@bytedance.com>
---
  hmp-commands-info.hx |  6 +++---
  monitor/misc.c       | 19 +++++++++++++++++++
  2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
index 3ffa24bd67..6023e2b5c5 100644
--- a/hmp-commands-info.hx
+++ b/hmp-commands-info.hx
@@ -100,9 +100,9 @@ ERST

{

          .name       = "registers",
-        .args_type  = "cpustate_all:-a",
-        .params     = "[-a]",
-        .help       = "show the cpu registers (-a: all - show register info for all 
cpus)",
+        .args_type  = "cpustate_all:-a,vcpu:i?",
+        .params     = "[-a] [vcpu]",
+        .help       = "show the cpu registers (-a: all - show register info for all 
cpus; vcpu: vCPU to query)",
          .cmd        = hmp_info_registers,
      },

diff --git a/monitor/misc.c b/monitor/misc.c

index 3d2312ba8d..b12309faad 100644
--- a/monitor/misc.c
+++ b/monitor/misc.c
@@ -307,6 +307,7 @@ int monitor_get_cpu_index(Monitor *mon)
  static void hmp_info_registers(Monitor *mon, const QDict *qdict)
  {
      bool all_cpus = qdict_get_try_bool(qdict, "cpustate_all", false);
+    int vcpu = qdict_get_try_int(qdict, "vcpu", -1);
      CPUState *cs;

if (all_cpus) {

@@ -314,6 +315,24 @@ static void hmp_info_registers(Monitor *mon, const QDict 
*qdict)
              monitor_printf(mon, "\nCPU#%d\n", cs->cpu_index);
              cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
          }
+    } else if (vcpu >= 0) {
+        CPUState *target_cs = NULL;
+
+        CPU_FOREACH(cs) {
+            if (cs->cpu_index == vcpu) {
+                target_cs = cs;
+                break;
+            }
+        }
+
+        if (!target_cs) {
+            monitor_printf(mon, "CPU#%d not available\n", vcpu);
+            return;
+        }
+
+        monitor_printf(mon, "\nCPU#%d\n", target_cs->cpu_index);
+        cpu_dump_state(target_cs, NULL, CPU_DUMP_FPU);
+        return;
      } else {
          cs = mon_get_cpu(mon);

--
zhenwei pi