Re: [PATCH v4 44/56] KVM: arm/arm64: vgic-new: vgic_kvm_device: access to VGIC registers

[Christoffer Dall <christoffer.dall@linaro.org>]

On Mon, May 16, 2016 at 10:53:32AM +0100, Andre Przywara wrote:
> From: Eric Auger <eric.auger@linaro.org>
> 
> This patch implements the switches for KVM_DEV_ARM_VGIC_GRP_DIST_REGS
> and KVM_DEV_ARM_VGIC_GRP_CPU_REGS API which allows the userspace to
> access VGIC registers.
> 
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
> Changelog v3 .. v4:
> - check for proper alignment on userland GIC accesses
> 
>  virt/kvm/arm/vgic/vgic-kvm-device.c | 53 +++++++++++++++++++++++++++++++++++--
>  virt/kvm/arm/vgic/vgic-mmio-v2.c    | 38 ++++++++++++++++++++++++++
>  virt/kvm/arm/vgic/vgic.h            |  1 +
>  3 files changed, 90 insertions(+), 2 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
> index a709097..78621283 100644
> --- a/virt/kvm/arm/vgic/vgic-kvm-device.c
> +++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
> @@ -226,6 +226,21 @@ void kvm_register_vgic_device(unsigned long type)
>  	}
>  }
>  
> +/** vgic_attr_regs_access: allows user space to read/write VGIC registers
> + *
> + * @dev: kvm device handle
> + * @attr: kvm device attribute
> + * @reg: address the value is read or written
> + * @is_write: write flag
> + *
> + */
> +static int vgic_attr_regs_access(struct kvm_device *dev,
> +				 struct kvm_device_attr *attr,
> +				 u32 *reg, bool is_write)
> +{
> +	return -ENXIO;
> +}
> +
>  /* V2 ops */
>  
>  static int vgic_v2_set_attr(struct kvm_device *dev,
> @@ -234,8 +249,23 @@ static int vgic_v2_set_attr(struct kvm_device *dev,
>  	int ret;
>  
>  	ret = vgic_set_common_attr(dev, attr);
> -	return ret;
> +	if (ret != -ENXIO)
> +		return ret;
> +
> +	switch (attr->group) {
> +	case KVM_DEV_ARM_VGIC_GRP_DIST_REGS:
> +	case KVM_DEV_ARM_VGIC_GRP_CPU_REGS: {
> +		u32 __user *uaddr = (u32 __user *)(long)attr->addr;
> +		u32 reg;
> +
> +		if (get_user(reg, uaddr))
> +			return -EFAULT;
>  
> +		return vgic_attr_regs_access(dev, attr, &reg, true);
> +	}
> +	}
> +
> +	return -ENXIO;
>  }
>  
>  static int vgic_v2_get_attr(struct kvm_device *dev,
> @@ -244,7 +274,23 @@ static int vgic_v2_get_attr(struct kvm_device *dev,
>  	int ret;
>  
>  	ret = vgic_get_common_attr(dev, attr);
> -	return ret;
> +	if (ret != -ENXIO)
> +		return ret;
> +
> +	switch (attr->group) {
> +	case KVM_DEV_ARM_VGIC_GRP_DIST_REGS:
> +	case KVM_DEV_ARM_VGIC_GRP_CPU_REGS: {
> +		u32 __user *uaddr = (u32 __user *)(long)attr->addr;
> +		u32 reg = 0;
> +
> +		ret = vgic_attr_regs_access(dev, attr, &reg, false);
> +		if (ret)
> +			return ret;
> +		return put_user(reg, uaddr);
> +	}
> +	}
> +
> +	return -ENXIO;
>  }
>  
>  static int vgic_v2_has_attr(struct kvm_device *dev,
> @@ -258,6 +304,9 @@ static int vgic_v2_has_attr(struct kvm_device *dev,
>  			return 0;
>  		}
>  		break;
> +	case KVM_DEV_ARM_VGIC_GRP_DIST_REGS:
> +	case KVM_DEV_ARM_VGIC_GRP_CPU_REGS:
> +		return vgic_v2_has_attr_regs(dev, attr);
>  	case KVM_DEV_ARM_VGIC_GRP_NR_IRQS:
>  		return 0;
>  	case KVM_DEV_ARM_VGIC_GRP_CTRL:
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> index 3925d4c..7189690 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> @@ -258,3 +258,41 @@ unsigned int vgic_v2_init_dist_iodev(struct vgic_io_device *dev)
>  
>  	return SZ_4K;
>  }
> +
> +int vgic_v2_has_attr_regs(struct kvm_device *dev, struct kvm_device_attr *attr)
> +{
> +	int nr_irqs = dev->kvm->arch.vgic.nr_spis + VGIC_NR_PRIVATE_IRQS;
> +	const struct vgic_register_region *regions;
> +	gpa_t addr;
> +	int nr_regions, i, len;
> +
> +	addr = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK;
> +
> +	switch (attr->group) {
> +	case KVM_DEV_ARM_VGIC_GRP_DIST_REGS:
> +		regions = vgic_v2_dist_registers;
> +		nr_regions = ARRAY_SIZE(vgic_v2_dist_registers);
> +		break;
> +	case KVM_DEV_ARM_VGIC_GRP_CPU_REGS:
> +		return -ENXIO;		/* TODO: describe CPU i/f regs also */
> +	default:
> +		return -ENXIO;
> +	}
> +
> +	/* We only support aligned 32-bit accesses. */
> +	if (addr & 3)
> +		return -ENXIO;
> +
> +	for (i = 0; i < nr_regions; i++) {
> +		if (regions[i].bits_per_irq)
> +			len = (regions[i].bits_per_irq * nr_irqs) / 8;
> +		else
> +			len = regions[i].len;
> +
> +		if (regions[i].reg_offset <= addr &&
> +		    regions[i].reg_offset + len > addr)
> +			return 0;
> +	}
> +
> +	return -ENXIO;
> +}
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index 6abc9a3..a264c5f 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -37,6 +37,7 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu);
>  void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr);
>  void vgic_v2_clear_lr(struct kvm_vcpu *vcpu, int lr);
>  void vgic_v2_set_underflow(struct kvm_vcpu *vcpu);
> +int vgic_v2_has_attr_regs(struct kvm_device *dev, struct kvm_device_attr *attr);
>  int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address,
>  			     enum vgic_type);
>  
> -- 
> 2.8.2
> 

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>