qemu: command: rework adding of default cpu model

Certain XML features that aren't in the <cpu> block map to -cpu
flags on the qemu cli. If one of these is specified but the user
didn't explicitly pass an XML <cpu> model, we need to format a
default model on the command line.

The current code handles this by sprinkling this default cpu handling
among all the different flag string formatting. Instead, switch it
to do this just once.

This alters some test output slightly: the previous code would
write the default -cpu in some cases when no flags were actually
added, so the output was redundant.
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NCole Robinson <crobinso@redhat.com>

src/qemu/qemu_command.c

@@ -6812,11 +6812,11 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
                         virQEMUCapsPtr qemuCaps)
 {
     virArch hostarch = virArchFromHost();
-    char *cpu = NULL;
+    char *cpu = NULL, *cpu_flags = NULL;
     bool hasHwVirt = false;
     const char *default_model;
-    bool have_cpu = false;
     int ret = -1;
+    virBuffer cpu_buf = VIR_BUFFER_INITIALIZER;
     virBuffer buf = VIR_BUFFER_INITIALIZER;
     size_t i;
 
@@ -6827,9 +6827,8 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
 
     if (def->cpu &&
         (def->cpu->mode != VIR_CPU_MODE_CUSTOM || def->cpu->model)) {
-        if (qemuBuildCpuModelArgStr(driver, def, &buf, qemuCaps) < 0)
+        if (qemuBuildCpuModelArgStr(driver, def, &cpu_buf, qemuCaps) < 0)
             goto cleanup;
-        have_cpu = true;
 
         /* Only 'svm' requires --enable-nesting. The nested 'vmx' patches now
          * simply hook off the CPU features. */
@@ -6867,8 +6866,7 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
             ((hostarch == VIR_ARCH_X86_64 &&
               strstr(def->emulator, "kvm")) ||
              strstr(def->emulator, "x86_64"))) {
-            virBufferAdd(&buf, default_model, -1);
-            have_cpu = true;
+            virBufferAdd(&cpu_buf, default_model, -1);
         }
     }
 
@@ -6878,21 +6876,14 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
 
         if (timer->name == VIR_DOMAIN_TIMER_NAME_KVMCLOCK &&
             timer->present != -1) {
-            virBufferAsprintf(&buf, "%s,%ckvmclock",
-                              have_cpu ? "" : default_model,
+            virBufferAsprintf(&buf, ",%ckvmclock",
                               timer->present ? '+' : '-');
-            have_cpu = true;
         } else if (timer->name == VIR_DOMAIN_TIMER_NAME_HYPERVCLOCK &&
                    timer->present == 1) {
-            virBufferAsprintf(&buf, "%s,hv_time",
-                              have_cpu ? "" : default_model);
-            have_cpu = true;
+            virBufferAddLit(&buf, ",hv_time");
         } else if (timer->name == VIR_DOMAIN_TIMER_NAME_TSC &&
                    timer->frequency > 0) {
-            virBufferAsprintf(&buf, "%s,tsc-frequency=%lu",
-                              have_cpu ? "" : default_model,
-                              timer->frequency);
-            have_cpu = true;
+            virBufferAsprintf(&buf, ",tsc-frequency=%lu", timer->frequency);
         }
     }
 
@@ -6903,10 +6894,7 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
         else
             sign = '-';
 
-        virBufferAsprintf(&buf, "%s,%ckvm_pv_eoi",
-                          have_cpu ? "" : default_model,
-                          sign);
-        have_cpu = true;
+        virBufferAsprintf(&buf, ",%ckvm_pv_eoi", sign);
     }
 
     if (def->features[VIR_DOMAIN_FEATURE_PVSPINLOCK]) {
@@ -6917,18 +6905,10 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
         else
             sign = '-';
 
-        virBufferAsprintf(&buf, "%s,%ckvm_pv_unhalt",
-                          have_cpu ? "" : default_model,
-                          sign);
-        have_cpu = true;
+        virBufferAsprintf(&buf, ",%ckvm_pv_unhalt", sign);
     }
 
     if (def->features[VIR_DOMAIN_FEATURE_HYPERV] == VIR_TRISTATE_SWITCH_ON) {
-        if (!have_cpu) {
-            virBufferAdd(&buf, default_model, -1);
-            have_cpu = true;
-        }
-
         for (i = 0; i < VIR_DOMAIN_HYPERV_LAST; i++) {
             switch ((virDomainHyperv) i) {
             case VIR_DOMAIN_HYPERV_RELAXED:
@@ -6964,22 +6944,12 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
 
     for (i = 0; i < def->npanics; i++) {
         if (def->panics[i]->model == VIR_DOMAIN_PANIC_MODEL_HYPERV) {
-            if (!have_cpu) {
-                virBufferAdd(&buf, default_model, -1);
-                have_cpu = true;
-            }
-
             virBufferAddLit(&buf, ",hv_crash");
             break;
         }
     }
 
     if (def->features[VIR_DOMAIN_FEATURE_KVM] == VIR_TRISTATE_SWITCH_ON) {
-        if (!have_cpu) {
-            virBufferAdd(&buf, default_model, -1);
-            have_cpu = true;
-        }
-
         for (i = 0; i < VIR_DOMAIN_KVM_LAST; i++) {
             switch ((virDomainKVM) i) {
             case VIR_DOMAIN_KVM_HIDDEN:
@@ -6996,12 +6966,8 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
 
     if (def->features[VIR_DOMAIN_FEATURE_PMU]) {
         virTristateSwitch pmu = def->features[VIR_DOMAIN_FEATURE_PMU];
-        if (!have_cpu)
-            virBufferAdd(&buf, default_model, -1);
-
         virBufferAsprintf(&buf, ",pmu=%s",
                           virTristateSwitchTypeToString(pmu));
-        have_cpu = true;
     }
 
     if (def->cpu && def->cpu->cache) {
@@ -7009,11 +6975,6 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
         bool hostOff = false;
         bool l3Off = false;
 
-        if (!have_cpu) {
-            virBufferAdd(&buf, default_model, -1);
-            have_cpu = true;
-        }
-
         switch (cache->mode) {
         case VIR_CPU_CACHE_MODE_EMULATE:
             virBufferAddLit(&buf, ",l3-cache=on");
@@ -7043,13 +7004,22 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
             virBufferAddLit(&buf, ",l3-cache=off");
     }
 
+    if (virBufferCheckError(&cpu_buf) < 0)
+        goto cleanup;
     if (virBufferCheckError(&buf) < 0)
         goto cleanup;
 
-    cpu = virBufferContentAndReset(&buf);
+    cpu = virBufferContentAndReset(&cpu_buf);
+    cpu_flags = virBufferContentAndReset(&buf);
+
+    if (cpu_flags && !cpu) {
+        if (VIR_STRDUP(cpu, default_model) < 0)
+            goto cleanup;
+    }
 
     if (cpu) {
-        virCommandAddArgList(cmd, "-cpu", cpu, NULL);
+        virCommandAddArg(cmd, "-cpu");
+        virCommandAddArgFormat(cmd, "%s%s", cpu, cpu_flags ? cpu_flags : "");
 
         if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_NESTING) && hasHwVirt)
             virCommandAddArg(cmd, "-enable-nesting");
@@ -7059,7 +7029,9 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
 
  cleanup:
     VIR_FREE(cpu);
+    VIR_FREE(cpu_flags);
     virBufferFreeAndReset(&buf);
+    virBufferFreeAndReset(&cpu_buf);
     return ret;
 }
 

tests/qemuxml2argvdata/qemuxml2argv-hyperv-off.args

@@ -8,7 +8,6 @@ QEMU_AUDIO_DRV=none \
 -name QEMUGuest1 \
 -S \
 -M pc \
--cpu qemu32 \
 -m 214 \
 -smp 6,sockets=6,cores=1,threads=1 \
 -uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \

tests/qemuxml2argvdata/qemuxml2argv-kvm-features-off.args

@@ -8,7 +8,6 @@ QEMU_AUDIO_DRV=none \
 -name QEMUGuest1 \
 -S \
 -M pc \
--cpu qemu32 \
 -m 214 \
 -smp 6,sockets=6,cores=1,threads=1 \
 -uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \