[libvirt] [PATCH v6 2/5] PowerPC : Add support for launching VM in 'compat' mode.

[Prerna Saxena]

>From 3ad5caf37bfa48e43c88660255e6a3bbb8afddeb Mon Sep 17 00:00:00 2001
From: Prerna Saxena <prerna at linux.vnet.ibm.com>
Date: Tue, 28 Oct 2014 15:05:59 +0530


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. As an 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 at linux.vnet.ibm.com>
Signed-off-by: Li Zhang <zhlcindy at linux.vnet.ibm.com>
Signed-off-by: Pradipta Kr. Banerjee <bpradip at in.ibm.com>
Acked-by: Michal Privoznik <mprivozn at redhat.com>
---
 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 96071d8..1333c35 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6222,7 +6222,9 @@ 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,
@@ -6237,6 +6239,12 @@ 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;
-- 
1.9.3

-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India