Newer S390 machines may drop support for features completely, rendering
guests operating with older CPU models incapable of running on said
machines. A manual effort to disable certain CPU features would be
required.
To alleviate this issue, a list of "deprecated" features are now
retained within QEMU, and a new "static-recommended" CPU model expansion
type has been created to allow a query of the host-model with deprecated
features explicitly disabled.
Signed-off-by: Collin Walling <wall...@linux.ibm.com>
---
qapi/machine-target.json | 8 +++++++-
target/s390x/cpu_features.c | 14 ++++++++++++++
target/s390x/cpu_features.h | 1 +
target/s390x/cpu_models_sysemu.c | 26 +++++++++++++++++++++-----
4 files changed, 43 insertions(+), 6 deletions(-)
diff --git a/qapi/machine-target.json b/qapi/machine-target.json
index f0a6b72414..4dc891809d 100644
--- a/qapi/machine-target.json
+++ b/qapi/machine-target.json
@@ -42,6 +42,12 @@
# to be migration-safe, but allows tooling to get an insight and
# work with model details.
#
+# @static-recommended: Expand to a static CPU model with property
+# changes suggested by the architecture. This is useful for
+# expanding a CPU model expected to operate in mixed
+# CPU-generation environments. The @static-recommended CPU
+# models are migration-safe.
+#
# Note: When a non-migration-safe CPU model is expanded in static
# mode, some features enabled by the CPU model may be omitted,
# because they can't be implemented by a static CPU model
@@ -55,7 +61,7 @@
# Since: 2.8
##
{ 'enum': 'CpuModelExpansionType',
- 'data': [ 'static', 'full' ] }
+ 'data': [ 'static', 'full', 'static-recommended' ] }
##
# @CpuModelCompareResult:
diff --git a/target/s390x/cpu_features.c b/target/s390x/cpu_features.c
index d28eb65845..efafc9711c 100644
--- a/target/s390x/cpu_features.c
+++ b/target/s390x/cpu_features.c
@@ -212,6 +212,20 @@ void s390_feat_bitmap_to_ascii(const S390FeatBitmap
features, void *opaque,
};
}
+void s390_get_deprecated_features(S390FeatBitmap features)
+{
+ static const int feats[] = {
+ /* CSSKE is deprecated on newer generations */
+ S390_FEAT_CONDITIONAL_SSKE,
+ S390_FEAT_BPB,
+ };
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(feats); i++) {
+ set_bit(feats[i], features);
+ }
+}
+
#define FEAT_GROUP_INIT(_name, _group, _desc) \
{ \
.name = _name, \
diff --git a/target/s390x/cpu_features.h b/target/s390x/cpu_features.h
index 87463f064d..5421762db5 100644
--- a/target/s390x/cpu_features.h
+++ b/target/s390x/cpu_features.h
@@ -68,6 +68,7 @@ void s390_add_from_feat_block(S390FeatBitmap features,
S390FeatType type,
uint8_t *data);
void s390_feat_bitmap_to_ascii(const S390FeatBitmap features, void *opaque,
void (*fn)(const char *name, void *opaque));
+void s390_get_deprecated_features(S390FeatBitmap features);
/* Definition of a CPU feature group */
typedef struct {
diff --git a/target/s390x/cpu_models_sysemu.c b/target/s390x/cpu_models_sysemu.c
index 63981bf36b..1aa3d076b4 100644
--- a/target/s390x/cpu_models_sysemu.c
+++ b/target/s390x/cpu_models_sysemu.c
@@ -176,7 +176,7 @@ static void qdict_add_enabled_feat(const char *name, void
*opaque)
/* convert S390CPUDef into a static CpuModelInfo */
static void cpu_info_from_model(CpuModelInfo *info, const S390CPUModel *model,
- bool delta_changes)
+ bool delta_changes, bool disable_dep_feats)
{
QDict *qdict = qdict_new();
S390FeatBitmap bitmap;
@@ -198,6 +198,13 @@ static void cpu_info_from_model(CpuModelInfo *info, const
S390CPUModel *model,
if (!bitmap_empty(bitmap, S390_FEAT_MAX)) {
s390_feat_bitmap_to_ascii(bitmap, qdict, qdict_add_enabled_feat);
}
+
+ /* features flagged as deprecated */
+ if (disable_dep_feats) {
+ bitmap_zero(bitmap, S390_FEAT_MAX);
+ s390_get_deprecated_features(bitmap);
+ s390_feat_bitmap_to_ascii(bitmap, qdict, qdict_add_disabled_feat);
+ }
} else {
/* expand all features */
s390_feat_bitmap_to_ascii(model->features, qdict,
@@ -221,6 +228,7 @@ CpuModelExpansionInfo
*qmp_query_cpu_model_expansion(CpuModelExpansionType type,
CpuModelExpansionInfo *expansion_info = NULL;
S390CPUModel s390_model;
bool delta_changes = false;
+ bool disable_dep_feats = false;
/* convert it to our internal representation */
cpu_model_from_info(&s390_model, model, &err);
@@ -229,9 +237,16 @@ CpuModelExpansionInfo
*qmp_query_cpu_model_expansion(CpuModelExpansionType type,
return NULL;
}
- if (type == CPU_MODEL_EXPANSION_TYPE_STATIC) {
+ switch (type) {
+ case CPU_MODEL_EXPANSION_TYPE_STATIC_RECOMMENDED:
+ disable_dep_feats = true;
+ /* fall through */
+ case CPU_MODEL_EXPANSION_TYPE_STATIC:
delta_changes = true;
- } else if (type != CPU_MODEL_EXPANSION_TYPE_FULL) {
+ break;
+ case CPU_MODEL_EXPANSION_TYPE_FULL:
+ break;
+ default:
error_setg(errp, "The requested expansion type is not supported.");
return NULL;
}
@@ -239,7 +254,8 @@ CpuModelExpansionInfo
*qmp_query_cpu_model_expansion(CpuModelExpansionType type,
/* convert it back to a static representation */
expansion_info = g_new0(CpuModelExpansionInfo, 1);
expansion_info->model = g_malloc0(sizeof(*expansion_info->model));
- cpu_info_from_model(expansion_info->model, &s390_model, delta_changes);
+ cpu_info_from_model(expansion_info->model, &s390_model,
+ delta_changes, disable_dep_feats);
return expansion_info;
}
@@ -388,7 +404,7 @@ CpuModelBaselineInfo
*qmp_query_cpu_model_baseline(CpuModelInfo *infoa,
baseline_info = g_new0(CpuModelBaselineInfo, 1);
baseline_info->model = g_malloc0(sizeof(*baseline_info->model));
- cpu_info_from_model(baseline_info->model, &model, true);
+ cpu_info_from_model(baseline_info->model, &model, true, false);
return baseline_info;
}
--
2.41.0
