linux-kernel - Re: [PATCH 1/3] KVM: introduce kvm->created

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Date:	Mon, 13 Jun 2016 16:43:06 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Christian Borntraeger <christian.borntraeger@...ibm.com>
Subject: Re: [PATCH 1/3] KVM: introduce kvm->created_vcpus

On Mon, 13 Jun 2016 15:25:30 +0200
Paolo Bonzini <pbonzini@...hat.com> wrote:

> The race between creating the irqchip and the first VCPU is
> currently fixed by checking the presence of an irqchip before
> updating kvm->online_vcpus, and undoing the whole VCPU creation
> if someone created the irqchip in the meanwhile.
> 
> Instead, introduce a new field in struct kvm that will count VCPUs
> under a mutex, without the atomic access and memory ordering that we
> need elsewhere to protect the vcpus array.  This also plugs the race
> and is more easily applicable in all similar circumstances.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>  include/linux/kvm_host.h |  8 ++++++++
>  virt/kvm/kvm_main.c      | 23 +++++++++++++++++------
>  2 files changed, 25 insertions(+), 6 deletions(-)

Reviewed-by: Cornelia Huck <cornelia.huck@...ibm.com>