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Subject: Re: [PATCH -next] x86/kvm: Fix build with CONFIG_SMP disabled
To:     Wang ShaoBo <bobo.shaobowang@huawei.com>
Cc:     weiyongjun1@huawei.com, huawei.libin@huawei.com,
        cj.chengjian@huawei.com, sean.j.christopherson@intel.com,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org
References: <20200929115013.3913359-1-bobo.shaobowang@huawei.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <38a60580-ef79-474f-030f-f15f2f1af6bf@redhat.com>
Date:   Tue, 29 Sep 2020 14:32:08 +0200
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On 29/09/20 13:50, Wang ShaoBo wrote:
> When CONFIG_SMP is disabled, build failed like this:
> 
> arch/x86/kernel/kvm.c: In function ‘kvm_alloc_cpumask’:
> arch/x86/kernel/kvm.c:823:35: error: ‘kvm_send_ipi_mask_allbutself’
>  undeclared (first use in this function); did you mean ‘apic_send_IPI_allbutself’?
>   apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
>                                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
>                                    apic_send_IPI_allbutself
> arch/x86/kernel/kvm.c:823:35: note: each undeclared identifier
>  is reported only once for each function it appears in
> 
> It is because the declaration of kvm_send_ipi_mask_allbutself() is guarded
> by CONFIG_SMP. kvm_send_ipi_mask_allbutself() do not need do anything at
> this time.
> 
> Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com>
> ---
>  arch/x86/kernel/kvm.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index a44398d2bc44..47d65864e29c 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -611,6 +611,13 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
>  	local_irq_enable();
>  	return 0;
>  }
> +
> +#else /* !CONFIG_SMP */
> +
> +static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
> +{
> +}
> +
>  #endif
>  
>  static void kvm_flush_tlb_others(const struct cpumask *cpumask,
> 

Hi,

a patch for this is already on the list, though I haven't committed it yet.

Thanks for the report.

Paolo