linux-kernel - Re: [PATCH 02/43] KVM: VMX: Set EDX at INIT with CPUID.0x1, Family-Model-Stepping

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Message-ID: <CAAeT=FyNo1CGvnamc3_J9EEQUn6WcdkMp50-QgmLYYVCFA2fZA@mail.gmail.com>
Date:   Tue, 18 May 2021 22:59:27 -0700
From:   Reiji Watanabe <reijiw@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/43] KVM: VMX: Set EDX at INIT with CPUID.0x1, Family-Model-Stepping

> @@ -4504,7 +4505,11 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
>
>         vmx->msr_ia32_umwait_control = 0;
>
> -       vmx->vcpu.arch.regs[VCPU_REGS_RDX] = get_rdx_init_val();
> +       eax = 1;
> +       if (!kvm_cpuid(vcpu, &eax, &dummy, &dummy, &dummy, true))
> +               eax = get_rdx_init_val();
> +       kvm_rdx_write(vcpu, eax);

Reviewed-by: Reiji Watanabe <reijiw@...gle.com>

For RESET, I assume that rdx should be set by userspace
when userspace changes CPUID.0x1.EAX.

BTW, I would think having a default CPUID for CPUID.(EAX=0x1)
would be better for consistency of a vCPU state for RESET.
I would think it doesn't matter practically anyway though.

Thanks,
Reiji