qemu: Implement multiple screen support for virDomainScreenshot

According to virDomainScreenshot() documentation, screens are
numbered sequentially.  e.g. having two graphics cards, both with
four heads, screen ID 5 addresses the second head on the second
card.

But apart from that, there's nothing special happening here.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_driver.c

@@ -3999,6 +3999,8 @@ qemuDomainScreenshot(virDomainPtr dom,
     qemuDomainObjPrivatePtr priv;
     char *tmp = NULL;
     int tmp_fd = -1;
+    size_t i;
+    const char *videoAlias = NULL;
     char *ret = NULL;
     bool unlink_tmp = false;
     virQEMUDriverConfigPtr cfg = NULL;
@@ -4020,15 +4022,37 @@ qemuDomainScreenshot(virDomainPtr dom,
     if (virDomainObjCheckActive(vm) < 0)
         goto endjob;
 
-    /* Well, even if qemu allows multiple graphic cards, heads, whatever,
-     * screenshot command does not */
-    if (screen) {
-        virReportError(VIR_ERR_INVALID_ARG,
-                       "%s", _("currently is supported only taking "
-                               "screenshots of screen ID 0"));
+    if (!vm->def->nvideos) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                      _("no screens to take screenshot from"));
         goto endjob;
     }
 
+    if (screen) {
+        if (!virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_SCREENDUMP_DEVICE)) {
+            virReportError(VIR_ERR_OPERATION_UNSUPPORTED, "%s",
+                           _("qemu does not allow specifying screen ID"));
+            goto endjob;
+        }
+
+        for (i = 0; i < vm->def->nvideos; i++) {
+            const virDomainVideoDef *video = vm->def->videos[i];
+
+            if (screen < video->heads) {
+                videoAlias = video->info.alias;
+                break;
+            }
+
+            screen -= video->heads;
+        }
+
+        if (i == vm->def->nvideos) {
+            virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                           _("no such screen ID"));
+            goto endjob;
+        }
+    }
+
     if (virAsprintf(&tmp, "%s/qemu.screendump.XXXXXX", cfg->cacheDir) < 0)
         goto endjob;
 
@@ -4041,7 +4065,7 @@ qemuDomainScreenshot(virDomainPtr dom,
     qemuSecuritySetSavedStateLabel(driver->securityManager, vm->def, tmp);
 
     qemuDomainObjEnterMonitor(driver, vm);
-    if (qemuMonitorScreendump(priv->mon, tmp) < 0) {
+    if (qemuMonitorScreendump(priv->mon, videoAlias, screen, tmp) < 0) {
         ignore_value(qemuDomainObjExitMonitor(driver, vm));
         goto endjob;
     }

src/qemu/qemu_monitor.c

@@ -3477,6 +3477,8 @@ qemuMonitorSendKey(qemuMonitorPtr mon,
 
 int
 qemuMonitorScreendump(qemuMonitorPtr mon,
+                      const char *device,
+                      unsigned int head,
                       const char *file)
 {
     VIR_DEBUG("file=%s", file);
@@ -3484,7 +3486,7 @@ qemuMonitorScreendump(qemuMonitorPtr mon,
     QEMU_CHECK_MONITOR(mon);
 
     if (mon->json)
-        return qemuMonitorJSONScreendump(mon, file);
+        return qemuMonitorJSONScreendump(mon, device, head, file);
     else
         return qemuMonitorTextScreendump(mon, file);
 }

src/qemu/qemu_monitor.h

@@ -886,6 +886,8 @@ int qemuMonitorArbitraryCommand(qemuMonitorPtr mon,
 int qemuMonitorInjectNMI(qemuMonitorPtr mon);
 
 int qemuMonitorScreendump(qemuMonitorPtr mon,
+                          const char *device,
+                          unsigned int head,
                           const char *file);
 
 int qemuMonitorSendKey(qemuMonitorPtr mon,

src/qemu/qemu_monitor_json.c

@@ -4483,6 +4483,8 @@ int qemuMonitorJSONSendKey(qemuMonitorPtr mon,
 }
 
 int qemuMonitorJSONScreendump(qemuMonitorPtr mon,
+                              const char *device,
+                              unsigned int head,
                               const char *file)
 {
     int ret = -1;
@@ -4490,6 +4492,8 @@ int qemuMonitorJSONScreendump(qemuMonitorPtr mon,
 
     cmd = qemuMonitorJSONMakeCommand("screendump",
                                      "s:filename", file,
+                                     "S:device", device,
+                                     "p:head", head,
                                      NULL);
 
     if (!cmd)

src/qemu/qemu_monitor_json.h

@@ -296,6 +296,8 @@ int qemuMonitorJSONSendKey(qemuMonitorPtr mon,
                            unsigned int nkeycodes);
 
 int qemuMonitorJSONScreendump(qemuMonitorPtr mon,
+                              const char *device,
+                              unsigned int head,
                               const char *file);
 
 int qemuMonitorJSONBlockStream(qemuMonitorPtr mon,

tests/qemumonitorjsontest.c

@@ -1348,7 +1348,7 @@ GEN_TEST_FUNC(qemuMonitorJSONDriveMirror, "vdb", "/foo/bar", NULL, 1024, 0, 0,
               VIR_DOMAIN_BLOCK_REBASE_SHALLOW | VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT)
 GEN_TEST_FUNC(qemuMonitorJSONBlockCommit, "vdb", "/foo/bar1", "/foo/bar2", NULL, 1024)
 GEN_TEST_FUNC(qemuMonitorJSONDrivePivot, "vdb")
-GEN_TEST_FUNC(qemuMonitorJSONScreendump, "/foo/bar")
+GEN_TEST_FUNC(qemuMonitorJSONScreendump, NULL, 0, "/foo/bar")
 GEN_TEST_FUNC(qemuMonitorJSONOpenGraphics, "spice", "spicefd", false)
 GEN_TEST_FUNC(qemuMonitorJSONNBDServerStart, "localhost", 12345, "test-alias")
 GEN_TEST_FUNC(qemuMonitorJSONNBDServerAdd, "vda", true)