From: Prerna Saxena <prerna@linux.vnet.ibm.com>
Date: Tue, 4 Nov 2014 22:52:44 +0530
Subject: [PATCH] PowerPC : Add support for launching VM in 'compat' mode.

PowerISA allows processors to run VMs in binary compatibility ("compat")
mode supporting an older version of ISA. QEMU has recently added support to
explicitly denote a VM running in compatibility mode through commit 6d9412ea
& 8dfa3a5e85. Now, a "compat" mode VM can be run by invoking this qemu
commandline on a POWER8 host:  -cpu host,compat=power7.

This patch allows libvirt to exploit cpu mode 'host-model' to describe this
new mode for PowerKVM guests. For example, when a user wants to request a
power7 vm to run in compatibility mode on a Power8 host, this can be
described in XML as follows :

  <cpu mode='host-model'>
    <model>power7</model>
  </cpu>

Signed-off-by: Prerna Saxena <prerna@linux.vnet.ibm.com>
Signed-off-by: Li Zhang <zhlcindy@linux.vnet.ibm.com>
Signed-off-by: Pradipta Kr. Banerjee <bpradip@in.ibm.com>
Acked-by: Michal Privoznik <mprivozn@redhat.com>
(cherry picked from commit addce06c9221f948072cd222b56ea9c3f70ec066)
---
 src/conf/cpu_conf.c     |  1 +
 src/cpu/cpu_powerpc.c   | 11 ++---------
 src/qemu/qemu_command.c | 10 +++++++++-
 3 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/conf/cpu_conf.c b/src/conf/cpu_conf.c
index 9b7fbb0..0e7a979 100644
--- a/src/conf/cpu_conf.c
+++ b/src/conf/cpu_conf.c
@@ -619,6 +619,7 @@ virCPUDefFormatBuf(virBufferPtr buf,
         return 0;
 
     formatModel = (def->mode == VIR_CPU_MODE_CUSTOM ||
+                   def->mode == VIR_CPU_MODE_HOST_MODEL ||
                    (flags & VIR_DOMAIN_XML_UPDATE_CPU));
     formatFallback = (def->type == VIR_CPU_TYPE_GUEST &&
                       (def->mode == VIR_CPU_MODE_HOST_MODEL ||
diff --git a/src/cpu/cpu_powerpc.c b/src/cpu/cpu_powerpc.c
index d591c18..4ea1835 100644
--- a/src/cpu/cpu_powerpc.c
+++ b/src/cpu/cpu_powerpc.c
@@ -562,8 +562,8 @@ ppcUpdate(virCPUDefPtr guest,
 static virCPUDefPtr
 ppcBaseline(virCPUDefPtr *cpus,
             unsigned int ncpus,
-            const char **models,
-            unsigned int nmodels,
+            const char **models ATTRIBUTE_UNUSED,
+            unsigned int nmodels ATTRIBUTE_UNUSED,
             unsigned int flags)
 {
     struct ppc_map *map = NULL;
@@ -583,13 +583,6 @@ ppcBaseline(virCPUDefPtr *cpus,
         goto error;
     }
 
-    if (!cpuModelIsAllowed(model->name, models, nmodels)) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                        _("CPU model %s is not supported by hypervisor"),
-                        model->name);
-        goto error;
-    }
-
     for (i = 0; i < ncpus; i++) {
         const struct ppc_vendor *vnd;
 
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index d60f274..34f6535 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6221,7 +6221,9 @@ qemuBuildCpuModelArgStr(virQEMUDriverPtr driver,
         *hasHwVirt = hasSVM > 0 ? true : false;
     }
 
-    if (cpu->mode == VIR_CPU_MODE_HOST_PASSTHROUGH) {
+    if ((cpu->mode == VIR_CPU_MODE_HOST_PASSTHROUGH) ||
+        ((cpu->mode == VIR_CPU_MODE_HOST_MODEL) &&
+          ARCH_IS_PPC64(def->os.arch))) {
         const char *mode = virCPUModeTypeToString(cpu->mode);
         if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_CPU_HOST)) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
@@ -6236,6 +6238,12 @@ qemuBuildCpuModelArgStr(virQEMUDriverPtr driver,
             goto cleanup;
         }
         virBufferAddLit(buf, "host");
+
+        if (ARCH_IS_PPC64(def->os.arch) &&
+            cpu->mode == VIR_CPU_MODE_HOST_MODEL) {
+            virBufferAsprintf(buf, ",compat=%s", def->cpu->model);
+        }
+
     } else {
         if (VIR_ALLOC(guest) < 0)
             goto cleanup;