linux-kernel - Re: [PATCH 07/13] KVM: monolithic: x86: remove __init section prefix from kvm_x86_cpu_has_kvm

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Message-ID: <232b6fcf-c441-7d85-00a4-43187e3393a6@redhat.com>
Date:   Tue, 5 Nov 2019 11:16:45 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Andrea Arcangeli <aarcange@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH 07/13] KVM: monolithic: x86: remove __init section prefix
 from kvm_x86_cpu_has_kvm_support

On 04/11/19 23:59, Andrea Arcangeli wrote:
> Adjusts the section prefixes of some KVM x86 code function because
> with the monolithic KVM model the section checker can now do a more
> accurate static analysis at build time. This also allows to build
> without CONFIG_SECTION_MISMATCH_WARN_ONLY=n.
> 
> The __init needs to be removed on vmx despite it's only svm calling it
> from kvm_x86_hardware_enable which is eventually called by
> hardware_enable_nolock() or there's a (potentially false positive)
> warning (false positive because this function isn't called in the vmx
> case). If this isn't needed the right cleanup isn't to put it in the
> __init section, but to drop it. As long as it's defined in vmx as a
> kvm_x86 operation, it's expectable that might eventually be called at
> runtime while hot plugging new CPUs.
> 
> Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 4 ++--
>  arch/x86/kvm/vmx/vmx.c          | 2 +-
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 2b03ec80f6d7..2ddc61fdcd09 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -998,7 +998,7 @@ struct kvm_lapic_irq {
>  	bool msi_redir_hint;
>  };
>  
> -extern __init int kvm_x86_cpu_has_kvm_support(void);
> +extern int kvm_x86_cpu_has_kvm_support(void);
>  extern __init int kvm_x86_disabled_by_bios(void);
>  extern int kvm_x86_hardware_enable(void);
>  extern void kvm_x86_hardware_disable(void);
> @@ -1190,7 +1190,7 @@ extern bool kvm_x86_apic_init_signal_blocked(struct kvm_vcpu *vcpu);
>  extern int kvm_x86_enable_direct_tlbflush(struct kvm_vcpu *vcpu);
>  
>  struct kvm_x86_ops {
> -	int (*cpu_has_kvm_support)(void);          /* __init */
> +	int (*cpu_has_kvm_support)(void);
>  	int (*disabled_by_bios)(void);             /* __init */
>  	int (*hardware_enable)(void);
>  	void (*hardware_disable)(void);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index e406707381a4..87e5d7276ea4 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2178,7 +2178,7 @@ void kvm_x86_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
>  	}
>  }
>  
> -__init int kvm_x86_cpu_has_kvm_support(void)
> +int kvm_x86_cpu_has_kvm_support(void)
>  {
>  	return cpu_has_vmx();
>  }
> 

I think we should eliminate all the complications in cpu_has_svm(), so
that svm_hardware_enable can use it.  I'll post a patch.

Paolo