On Sat, 13 Nov 2021 01:22:26 +0000,
Raghavendra Rao Ananta <rananta@xxxxxxxxxx> wrote:
>
> The upcoming patches need a way to detect if the VM, as
> a whole, has started. Hence, unionize kvm_vcpu_has_run_once()
> of all the vcpus of the VM and build kvm_vm_has_run_once()
> to achieve the functionality.
>
> No functional change intended.
>
> Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> ---
> include/linux/kvm_host.h | 2 ++
> virt/kvm/kvm_main.c | 17 +++++++++++++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index b373929c71eb..102e00c0e21c 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1854,4 +1854,6 @@ static inline bool kvm_vcpu_has_run_once(struct kvm_vcpu *vcpu)
> return vcpu->has_run_once;
> }
>
> +bool kvm_vm_has_run_once(struct kvm *kvm);
> +
> #endif
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1ec8a8e959b2..3d8d96e8f61d 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -4339,6 +4339,23 @@ static int kvm_vm_ioctl_get_stats_fd(struct kvm *kvm)
> return fd;
> }
>
> +bool kvm_vm_has_run_once(struct kvm *kvm)
> +{
> + int i, ret = false;
> + struct kvm_vcpu *vcpu;
> +
> + mutex_lock(&kvm->lock);
> +
> + kvm_for_each_vcpu(i, vcpu, kvm) {
> + ret = kvm_vcpu_has_run_once(vcpu);
> + if (ret)
> + break;
> + }
> +
> + mutex_unlock(&kvm->lock);
> + return ret;
> +}
This is horribly racy. Nothing prevents a vcpu from running behind
your back. If you want any sort of guarantee, look at what we do in
kvm_vgic_create(). Alexandru has patches that extract it to make it
generally available (at least for arm64).
M.
--
Without deviation from the norm, progress is not possible.
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