linux-kernel - Re: [PATCH v2 41/45] KVM: PPC: Move all vcpu init code into kvm_arch_vcpu

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Date:   Mon, 20 Jan 2020 14:46:58 +1100
From:   Paul Mackerras <paulus@...abs.org>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Marc Zyngier <maz@...nel.org>, James Hogan <jhogan@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-mips@...r.kernel.org, kvm-ppc@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kurz <groug@...d.org>
Subject: Re: [PATCH v2 41/45] KVM: PPC: Move all vcpu init code into
 kvm_arch_vcpu_create()

On Wed, Dec 18, 2019 at 01:55:26PM -0800, Sean Christopherson wrote:
> Fold init() into create() now that the two are called back-to-back by
> common KVM code (kvm_vcpu_init() calls kvm_arch_vcpu_init() as its last
> action, and kvm_vm_ioctl_create_vcpu() calls kvm_arch_vcpu_create()
> immediately thereafter).  Rinse and repeat for kvm_arch_vcpu_uninit()
> and kvm_arch_vcpu_destroy().  This paves the way for removing
> kvm_arch_vcpu_{un}init() entirely.
> 
> Note, calling kvmppc_mmu_destroy() if kvmppc_core_vcpu_create() fails
> may or may not be necessary.  Move it along with the more obvious call
> to kvmppc_subarch_vcpu_uninit() so as not to inadvertantly introduce a
> functional change and/or bug.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>

This doesn't compile.  I get:

  CC [M]  arch/powerpc/kvm/powerpc.o
/home/paulus/kernel/kvm/arch/powerpc/kvm/powerpc.c: In function ‘kvm_arch_vcpu_create’:
/home/paulus/kernel/kvm/arch/powerpc/kvm/powerpc.c:733:34: error: ‘kvmppc_decrementer_wakeup’ undeclared (first use in this function)
  vcpu->arch.dec_timer.function = kvmppc_decrementer_wakeup;
                                  ^
/home/paulus/kernel/kvm/arch/powerpc/kvm/powerpc.c:733:34: note: each undeclared identifier is reported only once for each function it appears in
/home/paulus/kernel/kvm/arch/powerpc/kvm/powerpc.c: At top level:
/home/paulus/kernel/kvm/arch/powerpc/kvm/powerpc.c:794:29: warning: ‘kvmppc_decrementer_wakeup’ defined but not used [-Wunused-function]
 static enum hrtimer_restart kvmppc_decrementer_wakeup(struct hrtimer *timer)
                             ^
make[3]: *** [/home/paulus/kernel/kvm/scripts/Makefile.build:266: arch/powerpc/kvm/powerpc.o] Error 1

The problem is that kvmppc_decrementer_wakeup() is a static function
defined in this file (arch/powerpc/kvm/powerpc.c) after
kvm_arch_vcpu_create() but before kvm_arch_vcpu_init().  You need a
forward static declaration of kvmppc_decrementer_wakeup() before
kvm_arch_vcpu_create(), or else move one or other function.

Paul.