[libvirt] [PATCH 03/12] qemu: caps: Start probing for egl-headless display type

[Erik Skultety]

QEMU 3.1 introduced the 'query-display-options' QMP command which in
itself isn't of any use to us since it can only provide information
during runtime as the information is based on what appears on the
cmdline. However, just by having the command in place allows us to
introspect the @DisplayOptions data type in the QAPI schema.

This patch implements the proper way of checking for the 'egl-headless'
display capability. Unfortunately, we can't get rid of the old code
which set the capability based on a specific QEMU (2.10) version just
yet as that would break backwards compatibility.

Signed-off-by: Erik Skultety <eskultet at redhat.com>
---
 src/qemu/qemu_capabilities.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index fde27010e4..90b76db034 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -1248,6 +1248,7 @@ static struct virQEMUCapsStringFlags virQEMUCapsQMPSchemaQueries[] = {
     { "screendump/arg-type/device", QEMU_CAPS_SCREENDUMP_DEVICE },
     { "block-commit/arg-type/*top",  QEMU_CAPS_ACTIVE_COMMIT },
     { "query-iothreads/ret-type/poll-max-ns", QEMU_CAPS_IOTHREAD_POLLING },
+    { "query-display-options/ret-type/+egl-headless", QEMU_CAPS_EGL_HEADLESS },
 };
 
 typedef struct _virQEMUCapsObjectTypeProps virQEMUCapsObjectTypeProps;
@@ -4122,11 +4123,6 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
         virQEMUCapsSet(qemuCaps, QEMU_CAPS_MACHINE_PSERIES_RESIZE_HPT);
     }
 
-    /* '-display egl-headless' cmdline option is supported since QEMU 2.10, but
-     * there's no way to probe it */
-    if (qemuCaps->version >= 2010000)
-        virQEMUCapsSet(qemuCaps, QEMU_CAPS_EGL_HEADLESS);
-
     /* no way to query for -numa dist */
     if (qemuCaps->version >= 2010000)
         virQEMUCapsSet(qemuCaps, QEMU_CAPS_NUMA_DIST);
@@ -4212,6 +4208,15 @@ virQEMUCapsInitQMPMonitor(virQEMUCapsPtr qemuCaps,
             virQEMUCapsClear(qemuCaps, QEMU_CAPS_SEV_GUEST);
     }
 
+    /* '-display egl-headless' cmdline option is supported since QEMU 2.10, but
+     * until QEMU 3.1 there hasn't been a way to probe it
+     *
+     * NOTE: One day in a future far far away, we can ditch this check
+     */
+    if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_EGL_HEADLESS) &&
+        qemuCaps->version >= 2010000)
+        virQEMUCapsSet(qemuCaps, QEMU_CAPS_EGL_HEADLESS);
+
     ret = 0;
  cleanup:
     return ret;
-- 
2.19.1