linux-kernel - Re: [PATCH v2 24/45] KVM: Add kvm_arch_vcpu_precreate() to handle pre-allocation issues

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Date:   Thu, 19 Dec 2019 20:28:35 +0100
From:   Cornelia Huck <cohuck@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Marc Zyngier <maz@...nel.org>, James Hogan <jhogan@...nel.org>,
        Paul Mackerras <paulus@...abs.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>,
        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 24/45] KVM: Add kvm_arch_vcpu_precreate() to handle
 pre-allocation issues

On Wed, 18 Dec 2019 13:55:09 -0800
Sean Christopherson <sean.j.christopherson@...el.com> wrote:

> Add a pre-allocation arch hook to handle checks that are currently done
> by arch specific code prior to allocating the vCPU object.  This paves
> the way for moving the allocation to common KVM code.
> 
> Acked-by: Christoffer Dall <christoffer.dall@....com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/mips/kvm/mips.c       |  5 +++++
>  arch/powerpc/kvm/powerpc.c |  5 +++++
>  arch/s390/kvm/kvm-s390.c   | 12 ++++++++----
>  arch/x86/kvm/x86.c         | 14 +++++++++-----
>  include/linux/kvm_host.h   |  1 +
>  virt/kvm/arm/arm.c         | 21 +++++++++++----------
>  virt/kvm/kvm_main.c        |  4 ++++
>  7 files changed, 43 insertions(+), 19 deletions(-)
> 

(...)

> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index d9e6bf3d54f0..57c6838dff37 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -3035,15 +3035,19 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
>  	return rc;
>  }
>  
> +int kvm_arch_vcpu_precreate(struct kvm *kvm, unsigned int id)
> +{
> +	if (!kvm_is_ucontrol(kvm) && !sca_can_add_vcpu(kvm, id))
> +		return -EINVAL;
> +	return 0;
> +}
> +
>  struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm,
>  				      unsigned int id)
>  {
>  	struct kvm_vcpu *vcpu;
>  	struct sie_page *sie_page;
> -	int rc = -EINVAL;
> -
> -	if (!kvm_is_ucontrol(kvm) && !sca_can_add_vcpu(kvm, id))
> -		goto out;
> +	int rc;

You might want to make this

int rc = -ENOMEM;

instead.

>  
>  	rc = -ENOMEM;
>  

(...)

Regardless,

Reviewed-by: Cornelia Huck <cohuck@...hat.com>