linux-kernel - Re: [PATCH 25/44] KVM: s390: Do s390 specific init without bouncing through kvm

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Date:   Thu, 3 Nov 2022 13:44:15 +0100
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        Aleksandar Markovic <aleksandar.qemu.devel@...il.com>,
        Anup Patel <anup@...infault.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Eric Farman <farman@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Atish Patra <atishp@...shpatra.org>,
        David Hildenbrand <david@...hat.com>, kvm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        kvmarm@...ts.cs.columbia.edu, linux-mips@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Isaku Yamahata <isaku.yamahata@...el.com>,
        Fabiano Rosas <farosas@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Chao Gao <chao.gao@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yuan Yao <yuan.yao@...el.com>
Subject: Re: [PATCH 25/44] KVM: s390: Do s390 specific init without bouncing
 through kvm_init()

On Wed,  2 Nov 2022 23:18:52 +0000
Sean Christopherson <seanjc@...gle.com> wrote:

> Move the guts of kvm_arch_init() into a new helper, __kvm_s390_init(),
> and invoke the new helper directly from kvm_s390_init() instead of
> bouncing through kvm_init().  Invoking kvm_arch_init() is the very
> first action performed by kvm_init(), i.e. this is a glorified nop.
> 
> Moving setup to __kvm_s390_init() will allow tagging more functions as
> __init, and emptying kvm_arch_init() will allow dropping the hook
> entirely once all architecture implementations are nops.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/s390/kvm/kvm-s390.c | 29 +++++++++++++++++++++++++----
>  1 file changed, 25 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 7fcd2d3b3558..e1c9980aae78 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -461,7 +461,7 @@ static void kvm_s390_cpu_feat_init(void)
>  	 */
>  }
>  
> -int kvm_arch_init(void *opaque)
> +static int __kvm_s390_init(void)
>  {
>  	int rc = -ENOMEM;
>  
> @@ -519,7 +519,7 @@ int kvm_arch_init(void *opaque)
>  	return rc;
>  }
>  
> -void kvm_arch_exit(void)
> +static void __kvm_s390_exit(void)
>  {
>  	gmap_unregister_pte_notifier(&gmap_notifier);
>  	gmap_unregister_pte_notifier(&vsie_gmap_notifier);
> @@ -533,6 +533,16 @@ void kvm_arch_exit(void)
>  	debug_unregister(kvm_s390_dbf_uv);
>  }
>  
> +int kvm_arch_init(void *opaque)
> +{
> +	return 0;
> +}
> +
> +void kvm_arch_exit(void)
> +{
> +
> +}
> +

I wonder at this point if it's possible to define kvm_arch_init and
kvm_arch_exit directly in kvm_main.c with __weak

>  /* Section: device related */
>  long kvm_arch_dev_ioctl(struct file *filp,
>  			unsigned int ioctl, unsigned long arg)
> @@ -5634,7 +5644,7 @@ static inline unsigned long nonhyp_mask(int i)
>  
>  static int __init kvm_s390_init(void)
>  {
> -	int i;
> +	int i, r;
>  
>  	if (!sclp.has_sief2) {
>  		pr_info("SIE is not available\n");
> @@ -5650,12 +5660,23 @@ static int __init kvm_s390_init(void)
>  		kvm_s390_fac_base[i] |=
>  			stfle_fac_list[i] & nonhyp_mask(i);
>  
> -	return kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
> +	r = __kvm_s390_init();
> +	if (r)
> +		return r;
> +
> +	r = kvm_init(NULL, sizeof(struct kvm_vcpu), 0, THIS_MODULE);
> +	if (r) {
> +		__kvm_s390_exit();
> +		return r;
> +	}
> +	return 0;
>  }
>  
>  static void __exit kvm_s390_exit(void)
>  {
>  	kvm_exit();
> +
> +	__kvm_s390_exit();
>  }
>  
>  module_init(kvm_s390_init);