On Fri, Mar 15, 2019 at 01:06:08PM +0100, Cédric Le Goater wrote:
> The 'destroy' method is currently used to destroy all devices when the
> VM is destroyed after the vCPUs have been freed.
>
> This new KVM ioctl exposes the same KVM device method. It acts as a
> software reset of the VM to 'destroy' selected devices when necessary
> and perform the required cleanups on the vCPUs. Called with the
> kvm->lock.
>
> The 'destroy' method could be improved by returning an error code.
>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx>
> ---
>
> Changes since v2 :
>
> - checked that device is owned by VM
>
> include/uapi/linux/kvm.h | 7 ++++++
> virt/kvm/kvm_main.c | 42 +++++++++++++++++++++++++++++++
> Documentation/virtual/kvm/api.txt | 20 +++++++++++++++
> 3 files changed, 69 insertions(+)
>
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 52bf74a1616e..d78fafa54274 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1183,6 +1183,11 @@ struct kvm_create_device {
> __u32 flags; /* in: KVM_CREATE_DEVICE_xxx */
> };
>
> +struct kvm_destroy_device {
> + __u32 fd; /* in: device handle */
> + __u32 flags; /* in: unused */
> +};
> +
> struct kvm_device_attr {
> __u32 flags; /* no flags currently defined */
> __u32 group; /* device-defined */
> @@ -1331,6 +1336,8 @@ struct kvm_s390_ucas_mapping {
> #define KVM_GET_DEVICE_ATTR _IOW(KVMIO, 0xe2, struct kvm_device_attr)
> #define KVM_HAS_DEVICE_ATTR _IOW(KVMIO, 0xe3, struct kvm_device_attr)
>
> +#define KVM_DESTROY_DEVICE _IOWR(KVMIO, 0xf0, struct kvm_destroy_device)
> +
> /*
> * ioctls for vcpu fds
> */
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e4881a8c2a6f..7b616a1d48cf 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -3026,6 +3026,34 @@ static int kvm_ioctl_create_device(struct kvm *kvm,
> return 0;
> }
>
> +static int kvm_ioctl_destroy_device(struct kvm *kvm,
> + struct kvm_destroy_device *dd)
> +{
> + struct fd f;
> + struct kvm_device *dev;
> +
> + f = fdget(dd->fd);
> + if (!f.file)
> + return -EBADF;
> +
> + dev = kvm_device_from_filp(f.file);
> + fdput(f);
> +
> + if (!dev)
> + return -ENODEV;
> +
> + if (dev->kvm != kvm)
> + return -EPERM;
> +
> + mutex_lock(&kvm->lock);
> + list_del(&dev->vm_node);
> + dev->ops->destroy(dev);
> + mutex_unlock(&kvm->lock);
> +
> + /* TODO: kvm_put_kvm() crashes the host on some occasion ? */
> + return 0;
> +}
> +
> static long kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
> {
> switch (arg) {
> @@ -3270,6 +3298,20 @@ static long kvm_vm_ioctl(struct file *filp,
> r = 0;
> break;
> }
> + case KVM_DESTROY_DEVICE: {
> + struct kvm_destroy_device dd;
> +
> + r = -EFAULT;
> + if (copy_from_user(&dd, argp, sizeof(dd)))
> + goto out;
> +
> + r = kvm_ioctl_destroy_device(kvm, &dd);
> + if (r)
> + goto out;
> +
> + r = 0;
> + break;
> + }
> case KVM_CHECK_EXTENSION:
> r = kvm_vm_ioctl_check_extension_generic(kvm, arg);
> break;
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 1db1435769b4..914471494602 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -3857,6 +3857,26 @@ number of valid entries in the 'entries' array, which is then filled.
> 'index' and 'flags' fields in 'struct kvm_cpuid_entry2' are currently reserved,
> userspace should not expect to get any particular value there.
>
> +4.119 KVM_DESTROY_DEVICE
> +
> +Capability: KVM_CAP_DEVICE_CTRL
> +Type: vm ioctl
> +Parameters: struct kvm_destroy_device (in)
> +Returns: 0 on success, -1 on error
> +Errors:
> + ENODEV: The device type is unknown or unsupported
> + EPERM: The device does not belong to the VM
> +
> + Other error conditions may be defined by individual device types or
> + have their standard meanings.
> +
> +Destroys an emulated device in the kernel.
> +
> +struct kvm_destroy_device {
> + __u32 fd; /* in: device handle */
> + __u32 flags; /* unused */
> +};
> +
> 5. The kvm_run structure
> ------------------------
>
--
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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