linux-kernel - Re: [PATCH v2 4/4] KVM: Do compatibility checks on hotplugged CPUs

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Message-ID: <YgMMlaMnjQRqwW6w@google.com>
Date:   Wed, 9 Feb 2022 00:36:37 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Chao Gao <chao.gao@...el.com>
Cc:     kvm@...r.kernel.org, pbonzini@...hat.com, kevin.tian@...el.com,
        tglx@...utronix.de, Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] KVM: Do compatibility checks on hotplugged CPUs

On Tue, Jan 18, 2022, Chao Gao wrote:
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 528741601122..83f87fb1fa0a 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4858,7 +4858,13 @@ static void hardware_enable_nolock(void *junk)
>  
>  static int kvm_online_cpu(unsigned int cpu)
>  {
> -	int ret = 0;
> +	int ret;
> +
> +	ret = kvm_arch_check_processor_compat();
> +	if (ret) {
> +		pr_warn("kvm: CPU%d is incompatible with online CPUs", cpu);

Hmm, I'd say omit the pr_warn() here too and instead add a pr_err() for the
setup_vmcs_config() path in vmx_check_processor_compat().

> +		return ret;
> +	}