virsh: expose virConnectGetDomainCapabilities

The API is exposed under 'domcapabilities' command. Currently, with
the variety of drivers that libvirt supports, none of the command
arguments is obligatory, but all are optional instead.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

tools/virsh-host.c

@@ -68,6 +68,70 @@ cmdCapabilities(vshControl *ctl, const vshCmd *cmd ATTRIBUTE_UNUSED)
     return true;
 }
 
+/*
+ * "domcapabilities" command
+ */
+static const vshCmdInfo info_domcapabilities[] = {
+    {.name = "help",
+     .data = N_("domain capabilities")
+    },
+    {.name = "desc",
+     .data = N_("Returns capabilities of emulator with respect to host and libvirt.")
+    },
+    {.name = NULL}
+};
+
+static const vshCmdOptDef opts_domcapabilities[] = {
+    {.name = "virttype",
+     .type = VSH_OT_STRING,
+     .help = N_("virtualization type (/domain/@type)"),
+    },
+    {.name = "emulatorbin",
+     .type = VSH_OT_STRING,
+     .help = N_("path to emulator binary (/domain/devices/emulator)"),
+    },
+    {.name = "arch",
+     .type = VSH_OT_STRING,
+     .help = N_("domain architecture (/domain/os/type/@arch)"),
+    },
+    {.name = "machine",
+     .type = VSH_OT_STRING,
+     .help = N_("machine type (/domain/os/type/@machine)"),
+    },
+    {.name = NULL}
+};
+
+static bool
+cmdDomCapabilities(vshControl *ctl, const vshCmd *cmd)
+{
+    bool ret = false;
+    char *caps = NULL;
+    const char *virttype = NULL;
+    const char *emulatorbin = NULL;
+    const char *arch = NULL;
+    const char *machine = NULL;
+    const unsigned int flags = 0; /* No flags so far */
+
+    if (vshCommandOptStringReq(ctl, cmd, "virttype", &virttype) < 0 ||
+        vshCommandOptStringReq(ctl, cmd, "emulatorbin", &emulatorbin) < 0 ||
+        vshCommandOptStringReq(ctl, cmd, "arch", &arch) < 0 ||
+        vshCommandOptStringReq(ctl, cmd, "machine", &machine) < 0)
+        return ret;
+
+    caps = virConnectGetDomainCapabilities(ctl->conn, emulatorbin,
+                                           arch, machine, virttype, flags);
+    if (!caps) {
+        vshError(ctl, "%s", _("failed to get emulator capabilities"));
+        goto cleanup;
+    }
+
+    vshPrint(ctl, "%s\n", caps);
+    ret = true;
+ cleanup:
+    VIR_FREE(caps);
+    return ret;
+}
+
 /*
  * "freecell" command
  */
@@ -1131,6 +1195,12 @@ const vshCmdDef hostAndHypervisorCmds[] = {
      .info = info_cpu_models,
      .flags = 0
     },
+    {.name = "domcapabilities",
+     .handler = cmdDomCapabilities,
+     .opts = opts_domcapabilities,
+     .info = info_domcapabilities,
+     .flags = 0
+    },
     {.name = "freecell",
      .handler = cmdFreecell,
      .opts = opts_freecell,

tools/virsh.pod

@@ -350,6 +350,41 @@ description see:
   L<http://libvirt.org/formatcaps.html>
 The XML also show the NUMA topology information if available.
 
+=item B<domcapabilities> [I<virttype>] [I<emulatorbin>]
+[I<arch>] [I<machine>]
+
+Print an XML document describing the domain capabilities for the
+hypervisor we are connected to using information either sourced from an
+existing domain or taken from the B<virsh capabilities> output. This may
+be useful if you intend to create a new domain and are curious if for
+instance it could make use of VFIO by creating a domain for the
+hypervisor with a specific emulator and architecture.
+
+Each hypervisor will have different requirements regarding which options
+are required and which are optional. A hypervisor can support providing
+a default value for any of the options.
+
+The I<virttype> option specifies the virtualization type used. The value
+to be used is either from the 'type' attribute of the <domain/> top
+level element from the domain XML or the 'type' attribute found within
+each <guest/> element from the B<virsh capabilities> output.  The
+I<emulatorbin> option specifies the path to the emulator. The value to
+be used is either the <emulator> element in the domain XML or the
+B<virsh capabilities> output. The I<arch> option specifies the
+architecture to be used for the domain. The value to be used is either
+the "arch" attribute from the domain's XML <os/> element and <type/>
+subelement or the "name" attribute of an <arch/> element from the
+B<virsh capabililites> output. The I<machine> specifies the machine type
+for the emulator. The value to be used is either the "machine" attribute
+from the domain's XML <os/> element and <type/> subelement or one from a
+list of machines from the B<virsh capabilities> output for a specific
+architecture and domain type.
+
+For the qemu hypervisor, a I<virttype> of either 'qemu' or 'kvm' must be
+supplied along with either the I<emulatorbin> or I<arch> in order to
+generate output for the default I<machine>.  Supplying a I<machine>
+value will generate output for the specific machine.
+
 =item B<inject-nmi> I<domain>
 
 Inject NMI to the guest.