Subject: [PATCH v3 1/4] ARM: KVM: Implement kvm_vcpu_preferred_target() function

From: [email-masked] (Marc Zyngier)
Date: Thu, 19 Sep 2013 15:27:54 +0100

On 19/09/13 14:11, Anup Patel wrote:
> This patch implements kvm_vcpu_preferred_target() function for
> KVM ARM which will help us implement KVM_ARM_PREFERRED_TARGET ioctl
> for user space.
> 
> Signed-off-by: Anup Patel <[email-masked]>
> Signed-off-by: Pranavkumar Sawargaonkar <[email-masked]>
> ---
>  arch/arm/kvm/guest.c              |   20 ++++++++++++++++++++
>  arch/arm64/include/asm/kvm_host.h |    1 +
>  2 files changed, 21 insertions(+)
> 
> diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
> index 152d036..b407e6c 100644
> --- a/arch/arm/kvm/guest.c
> +++ b/arch/arm/kvm/guest.c
> @@ -222,6 +222,26 @@ int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
>  	return kvm_reset_vcpu(vcpu);
>  }
>  
> +int kvm_vcpu_preferred_target(struct kvm_vcpu_init *init)
> +{
> +	int target = kvm_target_cpu();
> +
> +	if (target < 0)
> +		return -ENODEV;
> +
> +	memset(init, 0, sizeof(*init));
> +
> +	/* 
> +	 * For now, we return all optional features are available
> +	 * for preferred target. In future, we might have features
> +	 * available based on underlying host.
> +	 */
> +	init->target = (__u32)target;
> +	init->features[0] |= (1 << KVM_ARM_VCPU_POWER_OFF);

I'm in two minds about this feature reporting. I see they serve a
purpose, but they also duplicate capabilities, which is the standard way
to advertise what KVM can do.

It means we end up having to sync two reporting mechanism, and I feel
this is in general a bad idea.

Furthermore, KVM_ARM_VCPU_POWER_OFF is hardly a feature of the HW, but
rather a firmware emulation thing.

Peter, Christoffer: Thoughts?

	M.

> +	return 0;
> +}
> +
>  int kvm_arch_vcpu_ioctl_get_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
>  {
>  	return -EINVAL;
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index f318c43..b609db3 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -156,6 +156,7 @@ struct kvm_vcpu_stat {
>  struct kvm_vcpu_init;
>  int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
>  			const struct kvm_vcpu_init *init);
> +int kvm_vcpu_preferred_target(struct kvm_vcpu_init *init);
>  unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
>  int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);
>  struct kvm_one_reg;
> 

-- 
Jazz is not dead. It just smells funny...