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Re: [qemu-s390x] [PATCH v1] s390x/cpu_models: Add "-cpu max" support

From: Cornelia Huck
Subject: Re: [qemu-s390x] [PATCH v1] s390x/cpu_models: Add "-cpu max" support
Date: Fri, 27 Jul 2018 14:55:51 +0200

On Wed, 25 Jul 2018 11:12:33 +0200
David Hildenbrand <address@hidden> wrote:

> The "max" CPU model behaves like "-cpu host" when KVM is enabled, and like
> a CPU with the maximum possible feature set when TCG is enabled.
> While the "host" model can not be used under TCG ("kvm_required"), the
> "max" model can and "Enables all features supported by the accelerator in
> the current host".
> So we can treat "host" just as a special case of "max" (like x86 does).
> It differs to the "qemu" CPU model under TCG such that compatibility
> handling will not be performed and that some experimental CPU features
> not yet part of the "qemu" model might be indicated.
> These are right now under TCG (see "qemu_MAX"):
> - stfle53
> - msa5-base
> - zpci
> This will result right now in the following warning when starting QEMU TCG
> with the "max" model:
>     "qemu-system-s390x: warning: 'msa5-base' requires 'kimd-sha-512'."
> The "qemu" model (used as default in QEMU under TCG) will continue to
> work without such warnings. The "max" mdel in the current form
> might be interesting for kvm-unit-tests (where we would e.g. now also
> test "msa5-base").
> The "max" model is neither static nor migration safe (like the "host"
> model). It is independent of the machine but dependends on the accelerator.
> It can be used to detect the maximum CPU model also under TCG from upper
> layers without having to care about CPU model names for CPU model
> expansion.
> Signed-off-by: David Hildenbrand <address@hidden>
> ---
>  target/s390x/cpu_models.c | 81 +++++++++++++++++++++++++++------------
>  1 file changed, 56 insertions(+), 25 deletions(-)

So, what's the outcome? Can I merge this with the discussed minor
edits, or should I wait for a v2?

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