linux-kernel - Re: [PATCH 5/5] KVM: cpuid: remove has_leaf_count from struct kvm_cpuid

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Message-ID: <5a7d222e-3c49-2485-e11d-45c9e9ece8c8@redhat.com>
Date:   Wed, 10 Jul 2019 08:34:10 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jing Liu <jing2.liu@...ux.intel.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH 5/5] KVM: cpuid: remove has_leaf_count from struct
 kvm_cpuid_param

On 08/07/19 09:09, Jing Liu wrote:
> It seems the two func are introduced by 2b5e97e, as paravirtual cpuid.
> But when searching KVM_CPUID_SIGNATURE, there seems no caller requesting
> this cpuid. Meanwhile, I felt curious if KVM_CPUID_FEATURES is still in
> use but it seems kvm_update_cpuid() uses that. Not sure which spec
> introduces the latest pv cpuid.

Yes, KVM_CPUID_SIGNATURE is generally not very interesting for
userspace.  But KVM_CPUID_FEATURES is called here:

        for (w = 0; w < FEATURE_WORDS; w++) {
            /* Override only features that weren't set explicitly
             * by the user.
             */
            env->features[w] |=
                x86_cpu_get_supported_feature_word(w, cpu->migratable) &
                ~env->user_features[w] & \
                ~feature_word_info[w].no_autoenable_flags;
        }

Paolo