Re: [Qemu-devel] [PATCH for-2.9 15/17] target-i386: Define static "base" CPU model

[Eduardo Habkost]

On Mon, Dec 05, 2016 at 07:18:47PM +0100, David Hildenbrand wrote:
> Am 02.12.2016 um 22:18 schrieb Eduardo Habkost:
> > The query-cpu-model-expand QMP command needs at least one static
> > model, to allow the "static" expansion mode to be implemented.
> > Instead of defining static versions of every CPU model, define a
> > "base" CPU model that has absolutely no feature flag enabled.
> > 
> 
> Introducing separate ones makes feature lists presented to the user much
> shorter (and therefore easier to maintain). But I don't know how libvirt
> wants to deal with models on x86 in the future.

I understand that having a larger set of static models would make
expansions shorter. But I worry that by defining a complete set
of static models on x86 would require extra maintenance work on
the QEMU side with no visible benefit for libvirt.

I would like to hear from libvirt developers what they think. I
still don't know what they plan to use the type=static expansion
results for.

> 
> How long is the static expansion on a recent intel CPU?

CPU model "Broadwell" returns 165 entries on return.model.props:

(QEMU) query-cpu-model-expansion type=static model={"name":"Broadwell"}
{"return": {"migration-safe": true, "model": {"name": "base", "props": 
{"pfthreshold": false, "pku": false, "rtm": true, "tsc-deadline": true, 
"xstore-en": false, "tsc-scale": false, "abm": true, "ia64": false, "kvm-mmu": 
false, "xsaveopt": true, "tce": false, "smep": true, "fpu": true, "xcrypt": 
false, "clflush": true, "flushbyasid": false, "kvm-steal-time": false, "lm": 
true, "tsc": true, "adx": true, "fxsr": true, "tm": false, "xgetbv1": false, 
"xstore": false, "vme": false, "vendor": "GenuineIntel", "arat": true, "de": 
true, "aes": true, "pse": true, "ds-cpl": false, "tbm": false, "sse": true, 
"phe-en": false, "f16c": true, "ds": false, "mpx": false, "tsc-adjust": false, 
"avx512f": false, "avx2": true, "pbe": false, "cx16": true, "avx512pf": false, 
"movbe": true, "perfctr-nb": false, "ospke": false, "avx512ifma": false, 
"stepping": 2, "sep": true, "sse4a": false, "avx512dq": false, "avx512-4vnniw": 
false, "xsave": true, "pmm": false, "hle": true, "est": false, "xop": false, 
"smx": false, "monitor": false, "avx512er": false, "apic": true, "sse4.1": 
true, "sse4.2": true, "pause-filter": false, "lahf-lm": true, "kvm-nopiodelay": 
false, "acpi": false, "mmx": true, "osxsave": false, "pcommit": false, "mtrr": 
true, "clwb": false, "dca": false, "pdcm": false, "xcrypt-en": false, "3dnow": 
false, "invtsc": false, "tm2": false, "hypervisor": true, 
"kvmclock-stable-bit": false, "fxsr-opt": false, "pcid": true, "lbrv": false, 
"avx512-4fmaps": false, "svm-lock": false, "popcnt": true, "nrip-save": false, 
"avx512vl": false, "x2apic": true, "kvmclock": false, "smap": true, "family": 
6, "min-level": 13, "dtes64": false, "ace2": false, "fma4": false, "xtpr": 
false, "avx512bw": false, "nx": true, "lwp": false, "msr": true, "ace2-en": 
false, "decodeassists": false, "perfctr-core": false, "pge": true, "pn": false, 
"fma": true, "nodeid-msr": false, "cx8": true, "mce": true, "avx512cd": false, 
"cr8legacy": false, "mca": true, "pni": true, "rdseed": true, "osvw": false, 
"fsgsbase": true, "model-id": "Intel Core Processor (Broadwell)", "cmp-legacy": 
false, "kvm-pv-unhalt": false, "rdtscp": true, "mmxext": false, "cid": false, 
"vmx": false, "ssse3": true, "extapic": false, "pse36": true, "min-xlevel": 
2147483656, "ibs": false, "avx": true, "syscall": true, "umip": false, 
"invpcid": true, "bmi1": true, "bmi2": true, "vmcb-clean": false, "erms": true, 
"cmov": true, "misalignsse": false, "clflushopt": false, "pat": true, 
"3dnowprefetch": true, "rdpid": false, "pae": true, "wdt": false, "skinit": 
false, "pmm-en": false, "phe": false, "3dnowext": false, "lmce": false, "ht": 
false, "pdpe1gb": false, "kvm-pv-eoi": false, "npt": false, "xsavec": false, 
"pclmulqdq": true, "svm": false, "sse2": true, "ss": false, "topoext": false, 
"rdrand": true, "avx512vbmi": false, "kvm-asyncpf": false, "xsaves": false, 
"model": 61}}, "static": true}}


-- 
Eduardo