Subject: [PATCH v3 45/55] KVM: arm/arm64: vgic-new: Add userland access to VGIC dist registers

From: [email-masked] (Christoffer Dall)
Date: Thu, 12 May 2016 20:41:10 +0200

On Fri, May 06, 2016 at 11:45:58AM +0100, Andre Przywara wrote:
> Userland may want to save and restore the state of the in-kernel VGIC,
> so we provide the code which takes a userland request and translate
> that into calls to our MMIO framework.
> 
> Signed-off-by: Andre Przywara <[email-masked]>
> ---
>  virt/kvm/arm/vgic/vgic-kvm-device.c | 50 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 49 insertions(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
> index c952f6f..bb33af8 100644
> --- a/virt/kvm/arm/vgic/vgic-kvm-device.c
> +++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
> @@ -264,7 +264,55 @@ static int vgic_attr_regs_access(struct kvm_device *dev,

come to think of it, this is GICv2 specific right?

why don't we call it vgic_v2_attr_regs_access then?

and should it really live in this file?

>  				 struct kvm_device_attr *attr,
>  				 u32 *reg, bool is_write)
>  {
> -	return -ENXIO;
> +	gpa_t addr;
> +	int cpuid, ret, c;
> +	struct kvm_vcpu *vcpu, *tmp_vcpu;
> +
> +	cpuid = (attr->attr & KVM_DEV_ARM_VGIC_CPUID_MASK) >>
> +		 KVM_DEV_ARM_VGIC_CPUID_SHIFT;
> +	vcpu = kvm_get_vcpu(dev->kvm, cpuid);
> +	addr = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK;
> +
> +	mutex_lock(&dev->kvm->lock);
> +
> +	ret = vgic_init(dev->kvm);
> +	if (ret)
> +		goto out;
> +
> +	if (cpuid >= atomic_read(&dev->kvm->online_vcpus)) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	/*
> +	 * Ensure that no other VCPU is running by checking the vcpu->cpu
> +	 * field.  If no other VPCUs are running we can safely access the VGIC
> +	 * state, because even if another VPU is run after this point, that
> +	 * VCPU will not touch the vgic state, because it will block on
> +	 * getting the vgic->lock in kvm_vgic_sync_hwstate().
> +	 */

eh, I don't see us grabbing any vgic->lock (does that still exist?)
here?

> +	kvm_for_each_vcpu(c, tmp_vcpu, dev->kvm) {
> +		if (unlikely(tmp_vcpu->cpu != -1)) {
> +			ret = -EBUSY;
> +			goto out;
> +		}
> +	}
> +
> +	switch (attr->group) {
> +	case KVM_DEV_ARM_VGIC_GRP_CPU_REGS:
> +		ret = -EINVAL;
> +		break;
> +	case KVM_DEV_ARM_VGIC_GRP_DIST_REGS:
> +		ret = vgic_v2_dist_uaccess(vcpu, is_write, addr, reg);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +out:
> +	mutex_unlock(&dev->kvm->lock);
> +	return ret;
>  }
>  
>  /* V2 ops */
> -- 
> 2.7.3
> 
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Thanks,
-Christoffer