On Thu, Apr 11, 2019 at 03:53:01PM +0200, Cédric Le Goater wrote:
> When a P9 sPAPR VM boots, the CAS negotiation process determines which
> interrupt mode to use (XICS legacy or XIVE native) and invokes a
> machine reset to activate the chosen mode.
>
> To be able to switch from one interrupt mode to another, we introduce
> the capability to release a KVM device without destroying the VM. The
> KVM device interface is extended with a new 'release' method which is
> called when the file descriptor of the device is closed.
>
> Once 'release' is called, the 'destroy' method will not be called
> anymore as the device is removed from the device list of the VM.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
Kind of a hack, but a better way to solve this that doesn't involve
inordinate amounts of work doesn't occur to me.
> ---
> include/linux/kvm_host.h | 9 +++++++++
> virt/kvm/kvm_main.c | 13 +++++++++++++
> 2 files changed, 22 insertions(+)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 831d963451d8..722692e2f745 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -1240,6 +1240,15 @@ struct kvm_device_ops {
> */
> void (*destroy)(struct kvm_device *dev);
>
> + /*
> + * Release is an alternative method to free the device. It is
> + * called when the device file descriptor is closed. Once
> + * release is called, the destroy method will not be called
> + * anymore as the device is removed from the device list of
> + * the VM. kvm->lock is held.
> + */
> + void (*release)(struct kvm_device *dev);
> +
> int (*set_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
> int (*get_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
> int (*has_attr)(struct kvm_device *dev, struct kvm_device_attr *attr);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index ea2018ae1cd7..ea2619d5ca98 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2938,6 +2938,19 @@ static int kvm_device_release(struct inode *inode, struct file *filp)
> struct kvm_device *dev = filp->private_data;
> struct kvm *kvm = dev->kvm;
>
> + if (!dev)
> + return -ENODEV;
> +
> + if (dev->kvm != kvm)
> + return -EPERM;
> +
> + if (dev->ops->release) {
> + mutex_lock(&kvm->lock);
> + list_del(&dev->vm_node);
> + dev->ops->release(dev);
> + mutex_unlock(&kvm->lock);
> + }
> +
> kvm_put_kvm(kvm);
> return 0;
> }
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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