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Date: Wed, 26 Aug 2015 12:54:04 -0300
From: Eduardo Habkost <ehabkost@redhat.com>
Message-ID: <20150826155404.GH4230@thinpad.lan.raisama.net>
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Subject: Re: [Qemu-devel] [PATCH] target-i386: add a list of enforceable CPU
 models to the help output
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To: Peter Lieven <pl@kamp.de>
Cc: pbonzini@redhat.com, rth@twiddle.net, qemu-devel@nongnu.org, afaerber@suse.de

On Mon, Aug 24, 2015 at 11:17:04AM +0200, Peter Lieven wrote:
> this patch adds a probe that lists all enforceable and migrateable
> CPU models to the -cpu help output. The idea is to know a priory
> which CPU modules can be exposed to the user without loosing any
> feature flags.
> 
> Signed-off-by: Peter Lieven <pl@kamp.de>
[...]
> +/*
> + * Check if the CPU Definition is enforcable on the current host CPU
> + * and contains no unmigratable flags.
> + *
> + * Returns: true if the CPU can be enforced and migrated.
> + */
> +static bool x86_cpu_enforce_and_migratable(X86CPUDefinition *def)
> +{
> +    int i;
> +    for (i = 0; i < ARRAY_SIZE(feature_word_info); i++) {
> +        FeatureWordInfo *fw = &feature_word_info[i];
> +        uint32_t eax, ebx, ecx, edx, host;
> +        host_cpuid(fw->cpuid_eax, 0, &eax, &ebx, &ecx, &edx);

This isn't how you check if the CPU model can run in "enforce" mode.
Please read x86_cpu_filter_features().

Also, you can't tell if a CPU model is runnable in enforce mode unless
you know what's the accelerator being used (see
x86_cpu_filter_features()). How do you suggest we show
accelerator-specific information in help output?

-- 
Eduardo