From: zhenwei pi <pizhenwei@bytedance.com>
Date: Tue, 2 Aug 2022 07:37:20 +0000 (+0800)
Subject: monitor: Support specified vCPU registers
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=00d60cfcbda54b86ad9e09b20c7b71250dd6b19b;p=qemu.git

monitor: Support specified vCPU registers

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 registers 12' uses about 150us.

Cc: Darren Kenny <darren.kenny@oracle.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Message-Id: <20220802073720.1236988-2-pizhenwei@bytedance.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---

diff --git a/hmp-commands-info.hx b/hmp-commands-info.hx
index 188d9ece3b..e012035541 100644
--- a/hmp-commands-info.hx
+++ b/hmp-commands-info.hx
@@ -100,9 +100,11 @@ 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: show register info for all cpus;"
+                      " vcpu: specific vCPU to query; show the current CPU's registers if"
+                      " no argument is specified)",
         .cmd        = hmp_info_registers,
     },
 
diff --git a/monitor/misc.c b/monitor/misc.c
index 3d2312ba8d..6436a8786b 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) {
@@ -315,13 +316,18 @@ static void hmp_info_registers(Monitor *mon, const QDict *qdict)
             cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
         }
     } else {
-        cs = mon_get_cpu(mon);
+        cs = vcpu >= 0 ? qemu_get_cpu(vcpu) : mon_get_cpu(mon);
 
         if (!cs) {
-            monitor_printf(mon, "No CPU available\n");
+            if (vcpu >= 0) {
+                monitor_printf(mon, "CPU#%d not available\n", vcpu);
+            } else {
+                monitor_printf(mon, "No CPU available\n");
+            }
             return;
         }
 
+        monitor_printf(mon, "\nCPU#%d\n", cs->cpu_index);
         cpu_dump_state(cs, NULL, CPU_DUMP_FPU);
     }
 }