Previous version here (different subject line):
https://mail.gnu.org/archive/html/qemu-devel/2024-04/msg03200.html
Changelog
v3
- removed optional disable-deprecated-feats argument
- added deprecated-props array to CpuModelInfo struct
- amended cover letter language to reflect design
v2
- removed "static-recommended" expansion type
- implemented optional disable-deprecated-feats argument
---
The current implementation of query-cpu-model-expansion is lacking a way to
retrieve
CPU models with properties (i.e. features) that are flagged as deprecated. To
remedy
this, a list of deprecated-props has been appended to the CpuModelInfo struct,
and
will currently be reported by a query-cpu-model-expansion.
Check patch #2 description for an example output.
A simple interface is designed that contains an array of feature bits that are
flagged
as deprecated. This list may be easily populated with more features in the
future.
void s390_get_deprecated_features(S390FeatBitmap features)
{
static const int feats[] = {
/* CSSKE is deprecated on newer generations */
S390_FEAT_CONDITIONAL_SSKE,
S390_FEAT_BPB,
/* Deprecated on z16 */
S390_FEAT_CONSTRAINT_TRANSACTIONAL_EXE,
S390_FEAT_TRANSACTIONAL_EXE
};
int i;
for (i = 0; i < ARRAY_SIZE(feats); i++) {
set_bit(feats[i], features);
}
}
Use case example:
Newer s390 machines may signal the end-of-support for particular CPU features,
rendering guests operating with older CPU models incapable of running on
said machines. A manual effort to disable certain CPU features would be
required.
Reporting a list of deprecated features allows the user / management app to
take the next steps to ensure the guest is defined in a way that ensures
a migration in the future.
Collin L. Walling (2):
target/s390x: report deprecated-props in cpu-model-expansion reply
target/s390x: flag te and cte as deprecated
qapi/machine-target.json | 5 ++++-
target/s390x/cpu_features.c | 17 +++++++++++++++++
target/s390x/cpu_features.h | 1 +
target/s390x/cpu_models_sysemu.c | 6 ++++++
4 files changed, 28 insertions(+), 1 deletion(-)
--
2.43.0
