Re: [PATCH 2/3] add get/set irqchip ioctls for in kernel PIC live migration support

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

He, Qing wrote:
> This patch adds two new ioctls to dump and write kernel irqchips for
> save/restore and live migration. PIC s/r and l/m is implemented in this
> patch.
>
> Signed-off-by: Yaozu (Eddie) Dong <eddie.dong-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Signed-off-by: Qing He <qing.he-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>
>
> @@ -2902,6 +2949,39 @@ static long kvm_vm_ioctl(struct file *filp,
>  		}
>  		break;
>  	}
> +	case KVM_GET_IRQCHIP: {
> +		/* 0: PIC master, 1: PIC slave, 2: IOAPIC */
> +		struct kvm_irqchip chip;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&chip, argp, sizeof chip))
> +			goto out;
> +		if (irqchip_in_kernel(kvm)) {
> +			r = kvm_vm_ioctl_get_irqchip(kvm, &chip);
> +			if (r)
> +				goto out;
> +			r = -EFAULT;
> +			if (copy_to_user(argp, &chip, sizeof chip))
> +				goto out;
> +			r = 0;
> +		}
>   

We should return something other than EFAULT if !irqchip_in_kernel(). 
Maybe ENXIO?

> +		break;
> +	}
> +	case KVM_SET_IRQCHIP: {
> +		/* 0: PIC master, 1: PIC slave, 2: IOAPIC */
> +		struct kvm_irqchip chip;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&chip, argp, sizeof chip))
> +			goto out;
> +		if (irqchip_in_kernel(kvm)) {
> +			r = kvm_vm_ioctl_set_irqchip(kvm, &chip);
> +			if (r)
> +				goto out;
> +			r = 0;
> +		}
>   

Same here.

> +		break;
> +	}
>  	default:
>  		;
>  	}
> diff --git a/include/linux/kvm.h b/include/linux/kvm.h
> index 49d8124..1b49a7a 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -45,6 +45,38 @@ struct kvm_irq_level {
>  	__u32 level;
>  };
>  
> +
> +struct kvm_irqchip {
> +	__u32  chip_id;
>   
Add 32-bits of padding here in case the union needs to be 64-bit aligned
in the future.

> +        union {
> +		struct kvm_ioctl_pic pic;
>   

Reserve some space here so that other members can be added to the union
without changing the ioctl number.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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