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 14:21:17 +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 Thu, 3 Nov 2022 13:44:15 +0100
Claudio Imbrenda <imbrenda@...ux.ibm.com> wrote:

> 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

ah, nevermind, you get rid of them completely in the next patch

> 
> >  /* 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);  
>