[PATCH 2/7] qemu: Do not drop unknown CPU features from domain XML

[Jiri Denemark <jdenemar@xxxxxxxxxx>]

CPU features with policy='disable' which are unknown to QEMU may be
safely skipped when generating the -cpu command line, but we should
still keep them in the domain definition so that we can properly check
they are disabled after migrating the domain to a newer QEMU.

Signed-off-by: Jiri Denemark <jdenemar@xxxxxxxxxx>
---
 src/qemu/qemu_command.c | 13 ++++++++++++-
 src/qemu/qemu_process.c | 32 --------------------------------
 2 files changed, 12 insertions(+), 33 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index a0c9e5f8b3..b4888a5822 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6095,6 +6095,7 @@ qemuBuildCpuModelArgStr(virQEMUDriver *driver,
 {
     size_t i;
     virCPUDef *cpu = def->cpu;
+    g_auto(GStrv) knownFeatures = NULL;
 
     switch ((virCPUMode) cpu->mode) {
     case VIR_CPU_MODE_HOST_PASSTHROUGH:
@@ -6153,9 +6154,14 @@ qemuBuildCpuModelArgStr(virQEMUDriver *driver,
     if (cpu->vendor_id)
         virBufferAsprintf(buf, ",vendor=%s", cpu->vendor_id);
 
+    if (ARCH_IS_X86(def->os.arch) &&
+        virQEMUCapsGetCPUFeatures(qemuCaps, def->virtType, false, &knownFeatures) < 0)
+        return -1;
+
     for (i = 0; i < cpu->nfeatures; i++) {
         const char *featname =
             virQEMUCapsCPUFeatureToQEMU(def->os.arch, cpu->features[i].name);
+
         switch ((virCPUFeaturePolicy) cpu->features[i].policy) {
         case VIR_CPU_FEATURE_FORCE:
         case VIR_CPU_FEATURE_REQUIRE:
@@ -6164,7 +6170,12 @@ qemuBuildCpuModelArgStr(virQEMUDriver *driver,
 
         case VIR_CPU_FEATURE_DISABLE:
         case VIR_CPU_FEATURE_FORBID:
-            virBufferAsprintf(buf, ",%s=off", featname);
+            /* Features unknown to QEMU are implicitly disabled and we can just
+             * skip them. */
+            if (!knownFeatures ||
+                g_strv_contains((const char **) knownFeatures, cpu->features[i].name)) {
+                virBufferAsprintf(buf, ",%s=off", featname);
+            }
             break;
 
         case VIR_CPU_FEATURE_OPTIONAL:
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index a00066e88e..0e9e1a8efc 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -6212,26 +6212,6 @@ qemuProcessSetupHotpluggableVcpus(virDomainObj *vm,
 }
 
 
-static bool
-qemuProcessDropUnknownCPUFeatures(const char *name,
-                                  virCPUFeaturePolicy policy,
-                                  void *opaque)
-{
-    const char **features = opaque;
-
-    if (policy != VIR_CPU_FEATURE_DISABLE &&
-        policy != VIR_CPU_FEATURE_FORBID)
-        return true;
-
-    if (g_strv_contains(features, name))
-        return true;
-
-    /* Features unknown to QEMU are implicitly disabled, we can just drop them
-     * from the definition. */
-    return false;
-}
-
-
 static int
 qemuProcessUpdateGuestCPU(virDomainDef *def,
                           virQEMUCaps *qemuCaps,
@@ -6325,18 +6305,6 @@ qemuProcessUpdateGuestCPU(virDomainDef *def,
                                 &def->os.arch) < 0)
         return -1;
 
-    if (ARCH_IS_X86(def->os.arch)) {
-        g_auto(GStrv) features = NULL;
-
-        if (virQEMUCapsGetCPUFeatures(qemuCaps, def->virtType, false, &features) < 0)
-            return -1;
-
-        if (features &&
-            virCPUDefFilterFeatures(def->cpu, qemuProcessDropUnknownCPUFeatures,
-                                    features) < 0)
-            return -1;
-    }
-
     return 0;
 }
 
-- 
2.46.2