Re: [RFC PATCH v2 1/6] kvm: add device control API

["tiejun.chen" <tiejun.chen@windriver.com>]

On 04/02/2013 06:47 AM, Scott Wood wrote:
> Currently, devices that are emulated inside KVM are configured in a
> hardcoded manner based on an assumption that any given architecture
> only has one way to do it.  If there's any need to access device state,
> it is done through inflexible one-purpose-only IOCTLs (e.g.
> KVM_GET/SET_LAPIC).  Defining new IOCTLs for every little thing is
> cumbersome and depletes a limited numberspace.
>
> This API provides a mechanism to instantiate a device of a certain
> type, returning an ID that can be used to set/get attributes of the
> device.  Attributes may include configuration parameters (e.g.
> register base address), device state, operational commands, etc.  It
> is similar to the ONE_REG API, except that it acts on devices rather
> than vcpus.
>
> Both device types and individual attributes can be tested without having
> to create the device or get/set the attribute, without the need for
> separately managing enumerated capabilities.
>
> Signed-off-by: Scott Wood <scottwood@freescale.com>
> ---
>   Documentation/virtual/kvm/api.txt        |   70 ++++++++++++++++++++++++++++++
>   Documentation/virtual/kvm/devices/README |    1 +
>   arch/powerpc/include/asm/kvm_host.h      |    6 +++
>   arch/powerpc/include/asm/kvm_ppc.h       |    2 +
>   arch/powerpc/kvm/powerpc.c               |    7 +++
>   include/uapi/linux/kvm.h                 |   27 ++++++++++++
>   virt/kvm/kvm_main.c                      |   31 +++++++++++++
>   7 files changed, 144 insertions(+)
>   create mode 100644 Documentation/virtual/kvm/devices/README
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 976eb65..77328aa 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2173,6 +2173,76 @@ header; first `n_valid' valid entries with contents from the data
>   written, then `n_invalid' invalid entries, invalidating any previously
>   valid entries found.
>
> +4.79 KVM_CREATE_DEVICE
> +
> +Capability: KVM_CAP_DEVICE_CTRL
> +Type: vm ioctl
> +Parameters: struct kvm_create_device (in/out)
> +Returns: 0 on success, -1 on error
> +Errors:
> +  ENODEV: The device type is unknown or unsupported
> +  EEXIST: Device already created, and this type of device may not
> +          be instantiated multiple times
> +  ENOSPC: Too many devices have been created
> +
> +  Other error conditions may be defined by individual device types.
> +
> +Creates an emulated device in the kernel.  The file descriptor returned
> +in fd can be used with KVM_SET/GET/HAS_DEVICE_ATTR.
> +
> +If the KVM_CREATE_DEVICE_TEST flag is set, only test whether the
> +device type is supported (not necessarily whether it can be created
> +in the current vm).
> +
> +Individual devices should not define flags.  Attributes should be used
> +for specifying any behavior that is not implied by the device type
> +number.
> +
> +struct kvm_create_device {
> +	__u32	type;	/* in: KVM_DEV_TYPE_xxx */
> +	__u32	fd;	/* out: device handle */
> +	__u32	flags;	/* in: KVM_CREATE_DEVICE_xxx */
> +};
> +
> +4.80 KVM_SET_DEVICE_ATTR/KVM_GET_DEVICE_ATTR
> +
> +Capability: KVM_CAP_DEVICE_CTRL
> +Type: device ioctl
> +Parameters: struct kvm_device_attr
> +Returns: 0 on success, -1 on error
> +Errors:
> +  ENXIO:  The group or attribute is unknown/unsupported for this device
> +  EPERM:  The attribute cannot (currently) be accessed this way
> +          (e.g. read-only attribute, or attribute that only makes
> +          sense when the device is in a different state)
> +
> +  Other error conditions may be defined by individual device types.
> +
> +Gets/sets a specified piece of device configuration and/or state.  The
> +semantics are device-specific.  See individual device documentation in
> +the "devices" directory.  As with ONE_REG, the size of the data
> +transferred is defined by the particular attribute.
> +
> +struct kvm_device_attr {
> +	__u32	flags;		/* no flags currently defined */
> +	__u32	group;		/* device-defined */
> +	__u64	attr;		/* group-defined */
> +	__u64	addr;		/* userspace address of attr data */
> +};
> +
> +4.81 KVM_HAS_DEVICE_ATTR
> +
> +Capability: KVM_CAP_DEVICE_CTRL
> +Type: device ioctl
> +Parameters: struct kvm_device_attr
> +Returns: 0 on success, -1 on error
> +Errors:
> +  ENXIO:  The group or attribute is unknown/unsupported for this device
> +
> +Tests whether a device supports a particular attribute.  A successful
> +return indicates the attribute is implemented.  It does not necessarily
> +indicate that the attribute can be read or written in the device's
> +current state.  "addr" is ignored.
>
>   4.77 KVM_ARM_VCPU_INIT
>
> diff --git a/Documentation/virtual/kvm/devices/README b/Documentation/virtual/kvm/devices/README
> new file mode 100644
> index 0000000..34a6983
> --- /dev/null
> +++ b/Documentation/virtual/kvm/devices/README
> @@ -0,0 +1 @@
> +This directory contains specific device bindings for KVM_CAP_DEVICE_CTRL.
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index e34f8fe..e0caae2 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -370,6 +370,9 @@ struct kvmppc_booke_debug_reg {
>   	u64 dac[KVMPPC_BOOKE_MAX_DAC];
>   };
>
> +#define KVMPPC_IRQCHIP_NONE	0
> +#define KVMPPC_IRQCHIP_MPIC	1
> +
>   struct kvm_vcpu_arch {
>   	ulong host_stack;
>   	u32 host_pid;
> @@ -549,6 +552,9 @@ struct kvm_vcpu_arch {
>   	unsigned long magic_page_pa; /* phys addr to map the magic page to */
>   	unsigned long magic_page_ea; /* effect. addr to map the magic page to */
>
> +	int irqchip_type;
> +	void *irqchip_priv;
> +
>   #ifdef CONFIG_KVM_BOOK3S_64_HV
>   	struct kvm_vcpu_arch_shared shregs;
>
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h b/arch/powerpc/include/asm/kvm_ppc.h
> index f589307..f44932c 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -323,4 +323,6 @@ static inline ulong kvmppc_get_ea_indexed(struct kvm_vcpu *vcpu, int ra, int rb)
>   	return ea;
>   }
>
> +void mpic_put(void *priv);
> +
>   #endif /* __POWERPC_KVM_PPC_H__ */
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 16b4595..bdfa526 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -459,6 +459,13 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
>   	tasklet_kill(&vcpu->arch.tasklet);
>
>   	kvmppc_remove_vcpu_debugfs(vcpu);
> +
> +	switch (vcpu->arch.irqchip_type) {
> +	case KVMPPC_IRQCHIP_MPIC:
> +		mpic_put(vcpu->arch.irqchip_priv);
> +		break;
> +	}
> +
>   	kvmppc_core_vcpu_free(vcpu);
>   }
>
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 74d0ff3..20ce2d2 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -668,6 +668,7 @@ struct kvm_ppc_smmu_info {
>   #define KVM_CAP_PPC_EPR 86
>   #define KVM_CAP_ARM_PSCI 87
>   #define KVM_CAP_ARM_SET_DEVICE_ADDR 88
> +#define KVM_CAP_DEVICE_CTRL 89
>
>   #ifdef KVM_CAP_IRQ_ROUTING
>
> @@ -909,6 +910,32 @@ struct kvm_s390_ucas_mapping {
>   #define KVM_ARM_SET_DEVICE_ADDR	  _IOW(KVMIO,  0xab, struct kvm_arm_device_addr)
>
>   /*
> + * Device control API, available with KVM_CAP_DEVICE_CTRL
> + */
> +#define KVM_CREATE_DEVICE_TEST		1
> +
> +struct kvm_create_device {
> +	__u32	type;	/* in: KVM_DEV_TYPE_xxx */
> +	__u32	fd;	/* out: device handle */
> +	__u32	flags;	/* in: KVM_CREATE_DEVICE_xxx */
> +};
> +
> +struct kvm_device_attr {
> +	__u32	flags;		/* no flags currently defined */
> +	__u32	group;		/* device-defined */
> +	__u64	attr;		/* group-defined */
> +	__u64	addr;		/* userspace address of attr data */
> +};
> +
> +/* ioctl for vm fd */
> +#define KVM_CREATE_DEVICE	  _IOWR(KVMIO,  0xe0, struct kvm_create_device)
> +
> +/* ioctls for fds returned by KVM_CREATE_DEVICE */
> +#define KVM_SET_DEVICE_ATTR	  _IOW(KVMIO,  0xe1, struct kvm_device_attr)
> +#define KVM_GET_DEVICE_ATTR	  _IOW(KVMIO,  0xe2, struct kvm_device_attr)
> +#define KVM_HAS_DEVICE_ATTR	  _IOW(KVMIO,  0xe3, struct kvm_device_attr)
> +
> +/*
>    * ioctls for vcpu fds
>    */
>   #define KVM_RUN                   _IO(KVMIO,   0x80)
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index ff71541..ed033c0 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2158,6 +2158,17 @@ out:
>   }
>   #endif
>
> +static int kvm_ioctl_create_device(struct kvm *kvm,
> +				   struct kvm_create_device *cd)
> +{
> +	bool test = cd->flags & KVM_CREATE_DEVICE_TEST;
> +
> +	switch (cd->type) {
> +	default:
> +		return -ENODEV;
> +	}

Even after apply patch 5, looks here still misses something like:

	if (test)
		WARN_ON_ONCE(!cd->type);

	return -ENODEV;

Tiejun

> +}
> +
>   static long kvm_vm_ioctl(struct file *filp,
>   			   unsigned int ioctl, unsigned long arg)
>   {
> @@ -2272,6 +2283,26 @@ static long kvm_vm_ioctl(struct file *filp,
>   		break;
>   	}
>   #endif
> +	case KVM_CREATE_DEVICE: {
> +		struct kvm_create_device cd;
> +
> +		r = -EFAULT;
> +		if (copy_from_user(&cd, argp, sizeof(cd)))
> +			goto out;
> +
> +		mutex_lock(&kvm->lock);
> +		r = kvm_ioctl_create_device(kvm, &cd);
> +		mutex_unlock(&kvm->lock);
> +		if (r)
> +			goto out;
> +
> +		r = -EFAULT;
> +		if (copy_to_user(argp, &cd, sizeof(cd)))
> +			goto out;
> +
> +		r = 0;
> +		break;
> +	}
>   	default:
>   		r = kvm_arch_vm_ioctl(filp, ioctl, arg);
>   		if (r == -ENOTTY)
>