Clean up qemuBuildCommandLine to remove x86-specific

 assumptions from generic code.

This implements the minimal set of changes needed in libvirt to launch a
PowerPC-KVM based guest.
It removes x86-specific assumptions about choice of serial driver backend
from generic qemu guest commandline generation code.
It also restricts the ACPI capability to be available for an x86 or
x86_64 domain.
This is not a complete solution -- it still does not guarantee libvirt
the capability to flag non-supported options in guest XML. (Eg, an ACPI
specification in a PowerPC guest XML will still get processed, even
though qemu-system-ppc64 does not support it while qemu-system-x86_64 does.)
This drawback exists because libvirt falls back on qemu to query supported
features, and qemu '-h' blindly lists all capabilities -- irrespective
of whether they are available while emulating a given architecture or not.
The long-term solution would be for qemu to list out capabilities based
on architecture and platform -- so that libvirt can cleanly make out what
devices are supported on an arch (say 'ppc64') and platform (say, 'mac99').
Signed-off-by: NPrerna Saxena <prerna@linux.vnet.ibm.com>

src/qemu/qemu_command.c

@@ -4581,8 +4581,11 @@ qemuBuildCommandLine(virConnectPtr conn,
                 VIR_FREE(devstr);
 
                 virCommandAddArg(cmd, "-device");
-                virCommandAddArgFormat(cmd, "isa-serial,chardev=char%s,id=%s",
-                                       serial->info.alias, serial->info.alias);
+                if (!(devstr = qemuBuildChrDeviceStr(serial, def->os.arch,
+                                                     def->os.machine)))
+                   goto error;
+                virCommandAddArg(cmd, devstr);
+                VIR_FREE(devstr);
             } else {
                 virCommandAddArg(cmd, "-serial");
                 if (!(devstr = qemuBuildChrArgStr(&serial->source, NULL)))
@@ -5469,6 +5472,34 @@ qemuBuildCommandLine(virConnectPtr conn,
     return NULL;
 }
 
+/* This function generates the correct '-device' string for character
+ * devices of each architecture.
+ */
+char *
+qemuBuildChrDeviceStr(virDomainChrDefPtr serial,
+                       char *os_arch,
+                       char *machine)
+{
+    virBuffer cmd = VIR_BUFFER_INITIALIZER;
+
+    if (STREQ(os_arch, "ppc64") && STREQ(machine, "pseries"))
+        virBufferAsprintf(&cmd, "spapr-vty,chardev=char%s",
+                          serial->info.alias);
+    else
+        virBufferAsprintf(&cmd, "isa-serial,chardev=char%s,id=%s",
+                          serial->info.alias, serial->info.alias);
+
+    if (virBufferError(&cmd)) {
+        virReportOOMError();
+        goto error;
+    }
+
+    return virBufferContentAndReset(&cmd);
+
+ error:
+    virBufferFreeAndReset(&cmd);
+    return NULL;
+}
 
 /*
  * This method takes a string representing a QEMU command line ARGV set
@@ -6680,8 +6711,7 @@ virDomainDefPtr qemuParseCommandLine(virCapsPtr caps,
     def->maxvcpus = 1;
     def->vcpus = 1;
     def->clock.offset = VIR_DOMAIN_CLOCK_OFFSET_UTC;
-    def->features = (1 << VIR_DOMAIN_FEATURE_ACPI)
-        /*| (1 << VIR_DOMAIN_FEATURE_APIC)*/;
+
     def->onReboot = VIR_DOMAIN_LIFECYCLE_RESTART;
     def->onCrash = VIR_DOMAIN_LIFECYCLE_DESTROY;
     def->onPoweroff = VIR_DOMAIN_LIFECYCLE_DESTROY;
@@ -6716,6 +6746,9 @@ virDomainDefPtr qemuParseCommandLine(virCapsPtr caps,
     if (!def->os.arch)
         goto no_memory;
 
+    if (STREQ(def->os.arch, "i686")||STREQ(def->os.arch, "x86_64"))
+        def->features = (1 << VIR_DOMAIN_FEATURE_ACPI)
+        /*| (1 << VIR_DOMAIN_FEATURE_APIC)*/;
 #define WANT_VALUE()                                                   \
     const char *val = progargv[++i];                                   \
     if (!val) {                                                        \

src/qemu/qemu_command.h

@@ -53,6 +53,12 @@ virCommandPtr qemuBuildCommandLine(virConnectPtr conn,
                                    enum virNetDevVPortProfileOp vmop)
     ATTRIBUTE_NONNULL(1);
 
+/* Generate string for arch-specific '-device' parameter */
+char *
+qemuBuildChrDeviceStr (virDomainChrDefPtr serial,
+                       char *os_arch,
+                       char *machine);
+
 /* With vlan == -1, use netdev syntax, else old hostnet */
 char * qemuBuildHostNetStr(virDomainNetDefPtr net,
                            char type_sep,