Re: [patch 01/12] [PATCH] kvm-s390: ioctl to switch to user controlled virtual machines

[Avi Kivity <avi@redhat.com>]

On 12/01/2011 02:57 PM, Carsten Otte wrote:
> This patch introduces a new config option for user controlled kernel
> virtual machines. It introduces a new ioctl named
> KVM_S390_ENABLE_UCONTROL on the kvm file descriptor which allows for
> a one way transition from a regular kernel virtual machine to a
> user controlled virtual machine. The virtual machine must not have
> any memory slots installed, and no virtual cpus defined.
> Note that the user controlled virtual machines require CAP_SYS_ADMIN
> privileges.
>
> Signed-off-by: Carsten Otte <cotte@de.ibm.com>
> ---
> ---
>  arch/s390/kvm/Kconfig    |    9 +++++++++
>  arch/s390/kvm/kvm-s390.c |   30 ++++++++++++++++++++++++++++++
>  arch/s390/kvm/kvm-s390.h |   10 ++++++++++
>  include/linux/kvm.h      |    3 +++
>  4 files changed, 52 insertions(+)

Documentation/virtual/kvm/api.txt +++++++++++++++++++

>  
> +int kvm_s390_enable_ucontrol(struct kvm *kvm)
> +{
> +#ifdef CONFIG_KVM_UCONTROL
> +	int i;
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
> +	for (i = 0; i < KVM_MAX_VCPUS; i++)
> +		if (kvm->vcpus[i])
> +			return -EINVAL;
> +
> +	if (kvm->memslots->nmemslots)
> +		return -EPERM;

Why different errors?


> +
> +	if (kvm->arch.gmap)
> +		gmap_free(kvm->arch.gmap);
> +
> +	kvm->arch.gmap = NULL;

Locking?

What happens if a vcpu is created afterwards?

I guess you don't mind too much since this is a privileged interface for
a single purpose.

> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -654,6 +654,9 @@ struct kvm_clock_data {
>  					struct kvm_userspace_memory_region)
>  #define KVM_SET_TSS_ADDR          _IO(KVMIO,   0x47)
>  #define KVM_SET_IDENTITY_MAP_ADDR _IOW(KVMIO,  0x48, __u64)
> +/* enable ucontrol for s390 */
> +#define KVM_S390_ENABLE_UCONTROL  _IO(KVMIO,  0x49)
> +
>  /* Device model IOC */
>  #define KVM_CREATE_IRQCHIP        _IO(KVMIO,   0x60)
>  #define KVM_IRQ_LINE              _IOW(KVMIO,  0x61, struct kvm_irq_level)
>

#define KVM_CAP_S390_UCONTROL


-- 
error compiling committee.c: too many arguments to function