[PATCH 0/3] target: RFC: display deprecation note for '-cpu help'

[Daniel P . Berrangé]

When querying '-cpu help' there is no presentation of fact that a
CPU may be deprecated. The user just has to try it and see if they
get a depecation message at runtime.  The QMP command for querying
CPUs report a deprecation bool flag, but not the explanatory
reason.

The Icelake-Client CPU (removed in 6df39f5e583ca0f67bd934d1327f9ead2e3bd49c)
handled this by modifying the '.notes' section to add the word
'deprecated':

            {
                .version = 2,
                .note = "no TSX, deprecated",
                .alias = "Icelake-Client-noTSX",
                .props = (PropValue[]) {
                    { "hle", "off" },
                    { "rtm", "off" },
                    { /* end of list */ }
                },
            },

This relies on the person deprecating the CPU to remember to do this,
and is redundant when this info is already expressed in the
'.deprecation_note' field.

This short series suggests just modifying the '-cpu help'
formatter so that it displays the full deprecation message

eg

$ qemu-system-x86_64 -cpu help:
Available CPUs:
x86 486                   (alias configured by machine type) (deprecated: use 
at least 'Nehalem' / 'Opteron_G4', or 'host' / 'max')

I wonder if this is too verbose, and we should just do a
concise flag like approach, similar to QMP:

$ qemu-system-x86_64 -cpu help:
Available CPUs:
x86 486                   (alias configured by machine type) (deprecated)

leaving the full message to be displayed at runtime ? I'm slightly
inclined to the simpler more concise output.

This series touched x86_64, s390x, and aarch64 because that's all I
personally needed from a downstream POV, but any & all of the targets
would benefit from this. They have each implemneted the '-cpu help'
logic independantly though, and unifying that code is not entirely
straightforward.

Daniel P. Berrangé (3):
  target/i386: display deprecation note in '-cpu help'
  target/s390x: display deprecation note in '-cpu help'
  target/arm: display deprecation note in '-cpu help'

 target/arm/helper.c       | 10 +++++++++-
 target/i386/cpu.c         | 13 ++++++++++++-
 target/s390x/cpu_models.c | 28 +++++++++++++++++++++++-----
 3 files changed, 44 insertions(+), 7 deletions(-)

-- 
2.36.1